Changeset 587 for soft/giet_vm

Timestamp:

Jul 8, 2015, 3:35:36 PM (9 years ago)

Author:

alain

Message:

Major evolution of the FAT32 library: i
Introduce a distributed File-Caches architecture,
a distributed FAT-Cache, and a distributed Inodes-Tree structure.
Provide Posix-like system calls.

Location:

soft/giet_vm/giet_fat32

Files:

• fat32.c (modified) (16 diffs)
• fat32.h (modified) (3 diffs)

soft/giet_vm/giet_fat32/fat32.c

@@ -1 +1 @@
 //////////////////////////////////////////////////////////////////////////////////
-// File     : fat32.c 
-// Date     : 01/09/2013
-// Authors  : Marco Jankovic, Cesar Fuguet & Alain Greiner
+// Date     : 01/06/2015
+// Authors  : Alain Greiner
 // Copyright (c) UPMC-LIP6
 //////////////////////////////////////////////////////////////////////////////////
 // The fat32.h and fat32.c files define a library of access functions
-// to a FAT32 disk on a block device. It is intended to be used
-// by the GIET_VM nano-kernel for both the boot code and the kernel code.
+// to a FAT32 disk on a block device. It is intended to be used by both 
+// the boot code and the kernel code.
 //////////////////////////////////////////////////////////////////////////////////
 // Implementation notes:
@@ -13 +12 @@
 //    the block device. The physical sector size is supposed to be 512 bytes.
 // 2. the "cluster" variable is actually a cluster index. A cluster contains
-//    typically 8 sectors (4K bytes) and the cluster index is a 32 bits word.
-// 3. This FAT32 library uses a FAT cache whose storage capacity is one sector.
+//    8 sectors (4K bytes) and the cluster index is a 32 bits word.
+// 3. Each file or directory referenced by the software is represented
+//    by an "inode". The set of "inodes" is organised as a tree, that is 
+//    a sub-tree of the complete file system existing on the block device.
+// 4. A given file can be referenced by several software tasks, and each task
+//    will use a private handler, called a "file descriptor", allocated by the OS
+//    when the task open the file, that is organised as an indexed array.
+// 5. This FAT32 library implements (N+1) caches : one private "File_ Cache" 
+//    for each referenced file or directory, and a specific "Fat_Cache" for 
+//    the FAT itself. Each cache contain a variable number of clusters that are
+//    dynamically allocated when they are accessed, and organised as a 64-Tree.
+//////////////////////////////////////////////////////////////////////////////////
+// General Debug Policy:
+// The global variable GIET_DEBUG_FAT is defined in the giet_config.h file.
+// The debug is activated if (proctime > GIET_DEBUG_FAT) && (GIET_DEBUG_FAT != 0)
+// The GIET_DEBUG_FAT bit 0 defines the level of debug:
+//    if   (GIET_DEBUG_FAT & 0x1)    => detailed debug 
+//    else                           => external functions only
 //////////////////////////////////////////////////////////////////////////////////
 
@@ -22 +37 @@
 #include <utils.h>
 #include <vmem.h>
+#include <kernel_malloc.h>
 #include <bdv_driver.h>
 #include <hba_driver.h>
@@ -30 +46 @@
 
 //////////////////////////////////////////////////////////////////////////////////
-//      Global variable : internal FAT representation
-//////////////////////////////////////////////////////////////////////////////////
-
-extern fat32_fs_t _fat;
-
-extern unsigned int _ptabs_vaddr[GIET_NB_VSPACE_MAX][X_SIZE][Y_SIZE];
-  
+//               Global variables 
+//////////////////////////////////////////////////////////////////////////////////
+
+// Fat-Descriptor
+__attribute__((section(".kdata")))
+fat_desc_t _fat __attribute__((aligned(64))); 
+
+// buffer used by boot code as a simple cache when scanning FAT
+__attribute__((section(".kdata")))
+unsigned char  _fat_buffer_fat[4096] __attribute__((aligned(64)));
+
+// buffer used by boot code as a simple cache when scanning a directory in DATA region
+__attribute__((section(".kdata")))
+unsigned char  _fat_buffer_data[4096] __attribute__((aligned(64)));
+
+// lba of cluster in fat_buffer_fat
+__attribute__((section(".kdata")))
+unsigned int   _fat_buffer_fat_lba;
+
+// lba of cluster in fat_buffer_data 
+__attribute__((section(".kdata")))
+unsigned int   _fat_buffer_data_lba;
+
+//////////////////////////////////////////////////////////////////////////////////
+//////////////////////////////////////////////////////////////////////////////////
+//                  Static functions declaration
+//////////////////////////////////////////////////////////////////////////////////
+//////////////////////////////////////////////////////////////////////////////////
+
+
+///////////////////////////////////////////////////////////////////////////////////
+// This debug function displays the content of a 512 bytes buffer "buf",
+// with an identifier defined by the "string" and "block_id" arguments.
+///////////////////////////////////////////////////////////////////////////////////
+
+#if GIET_DEBUG_FAT
+static void _display_one_block( unsigned char* buf,
+                                char*          string,
+                                unsigned int   block_id );
+#endif
+
+//////////////////////////////////////////////////////////////////////////////////
+// This debug function displays the FAT descriptor. 
+//////////////////////////////////////////////////////////////////////////////////
+
+#if GIET_DEBUG_FAT
+static void _display_fat_descriptor();
+#endif
+
 /////////////////////////////////////////////////////////////////////////////////
-// This function computes the memory buffer physical address, and calls 
-// the proper IOC driver depending on the subtype (BDV / HBA / SDC / SPI / RDK). 
-// The use_irq argument allows to activate the descheduling mode, if it 
-// supported by the IOC driver subtype
+// This debug function displays the sequence of clusters allocated to a 
+// file (or directory) identified by the "inode" argument.
 /////////////////////////////////////////////////////////////////////////////////
-// Return 0 in case of success, return -1 in case of error
+
+#if GIET_DEBUG_FAT
+static void _display_clusters_list( fat_inode_t* inode );
+#endif
+
 /////////////////////////////////////////////////////////////////////////////////
-static
-int _fat_ioc_access( unsigned int use_irq,
-                     unsigned int to_mem,
-                     unsigned int lba,
-                     unsigned int buf_vaddr,
-                     unsigned int count ) 
+// The following function transfers one or several blocks between the device 
+// and a memory buffer identified by a virtual address.
+// It computes the memory buffer physical address, and calls the proper 
+// IOC driver depending on the subtype (BDV / HBA / SDC / SPI / RDK). 
+// The use_irq argument allows to activate the descheduling mode,
+// if it supported by the IOC driver subtype
+// It returns O  in case of success.
+// It returns -1 in case of error.
+/////////////////////////////////////////////////////////////////////////////////
+
+static int _fat_ioc_access( unsigned int use_irq,
+                            unsigned int to_mem,
+                            unsigned int lba,
+                            unsigned int buf_vaddr,
+                            unsigned int count );
+
+//////////////////////////////////////////////////////////////////////////////////
+// The following function returns in the "desc" argument a pointer on a buffer 
+// descriptor contained in a File_Cache, or in the Fat_Cache. 
+// The searched buffer is idenfified by the "inode" and "cluster_id" arguments.
+// If the "inode" pointer is not NULL, the searched cache is a File-Cache.
+// If the "inode" pointer is NULL, the searched cache is the Fat-Cache, 
+// The "cluster_id" argument is the buffer index in the file (or in the FAT). 
+// In case of miss, it allocate a 4 Kbytes buffer and a cluster descriptor 
+// from the local kernel heap, and calls the _fat_ioc_access() function to load 
+// the missing cluster from the block device.
+// It returns O  in case of success.
+// It returns 1 in case of error.
+//////////////////////////////////////////////////////////////////////////////////
+
+static unsigned int _get_buffer_from_cache( fat_inode_t*        inode,
+                                            unsigned int        cluster_id,
+                                            fat_cache_desc_t**  desc );
+
+////////////////////////////////////////////////////////////////////////////////
+// This function extract a (partial) name from a LFN directory entry.
+////////////////////////////////////////////////////////////////////////////////
+
+static void _get_name_from_long( unsigned char* buffer, 
+                                 char*          name );
+
+////////////////////////////////////////////////////////////////////////////////
+// The following function extract a name from a NORMAL directory entry.
+////////////////////////////////////////////////////////////////////////////////
+
+static void _get_name_from_short( unsigned char* buffer,
+                                  char*          name );
+
+//////////////////////////////////////////////////////////////////////////////////
+// This function returns the number of levels of a File-Cache (or Fat-Cache)
+// from the size of the file (or FAT).
+//////////////////////////////////////////////////////////////////////////////////
+
+static inline unsigned int _get_levels_from_size( unsigned int size );
+
+///////////////////////////////////////////////////////////////////////////////////
+// The following function analyses the "pathname" argument, from the character 
+// defined by the "nb_read" argument.
+// It copies the found name in the "name" buffer (without '/'), 
+// and updates the "nb_read" argument.
+// It returns 0 if success.
+// It returns 1 if one name length > NAME_MAX_SIZE characters
+///////////////////////////////////////////////////////////////////////////////////
+
+static unsigned int _get_name_from_path( char*          pathname,
+                                         char*          name,
+                                         unsigned int*  nb_read );
+
+////////////////////////////////////////////////////////////////////////////////
+// The following function scan the "pathname" argument, and copies in the
+// "name" buffer the last name in path (leaf name).
+// It returns 0 if success.
+// It returns 1 if one name length > NAME_MAX_SIZE characters
+////////////////////////////////////////////////////////////////////////////////
+static unsigned int _get_last_name( char*   pathname,
+                                    char*   name );
+
+//////////////////////////////////////////////////////////////////////////////////
+// The following function access the Fat-Cache and returns in the "value"
+// argument the content of the FAT slot identified by the "cluster" argument.
+// It loads the missing cluster from block device into cache in case of miss.
+// It returns 0 if success.
+// It returns 1 if error.
+//////////////////////////////////////////////////////////////////////////////////
+
+static unsigned int _get_fat_entry( unsigned int  cluster,
+                                    unsigned int* value );
+
+//////////////////////////////////////////////////////////////////////////////////
+// The following function writes a new "value" in the Fat-Cache, in the slot 
+// identified by the "cluster" argument.  
+// It loads the missing cluster from block device into cache in case of miss.
+// It returns 0 if success,
+// It returns 1 if error.
+//////////////////////////////////////////////////////////////////////////////////
+
+static unsigned int _set_fat_entry( unsigned int  cluster,
+                                    unsigned int  value );
+
+//////////////////////////////////////////////////////////////////////////////////
+// The following function introduces the inode identified by the "child" argument,
+// as a new child of the "parent" inode in the Inode-Tree.
+// All checking are supposed to be done by the caller.
+// Nor the File-Cache, neither the block device are modified.
+//////////////////////////////////////////////////////////////////////////////////
+
+static void _add_inode_in_tree( fat_inode_t*  child,
+                                fat_inode_t*  parent );
+
+//////////////////////////////////////////////////////////////////////////////////
+// The following function removes one inode identified by the "inode" argument 
+// from the Inode-Tree. All checking are supposed to be done by the caller.
+// Nor the File-Cache, neither the block device are modified.
+//////////////////////////////////////////////////////////////////////////////////
+
+static void _remove_inode_from_tree( fat_inode_t* inode );
+
+//////////////////////////////////////////////////////////////////////////////////
+// This recursive function scan one File-Cache (or Fat-Cache) from root to leaves,
+// to writes all dirty clusters to block device, and reset the dirty bits.
+// The cache is identified by the "root" an "levels" arguments.
+// The "string" argument is only used for debug : inode name or Fat.
+// It returns 0 if success.
+// It returns 1 if error.
+//////////////////////////////////////////////////////////////////////////////////
+
+static unsigned int _update_device_from_cache( unsigned int      levels,
+                                               fat_cache_node_t* root,
+                                               char*             string );
+
+//////////////////////////////////////////////////////////////////////////////////
+// The following function access directly the FS_INFO block on the block device, 
+// to update the "first_free_cluster" and "free_clusters_number" values,
+// using only the Fat-Descriptor single block buffer.
+// It return 0 in case of success.
+// It return 1 in case of error.
+//////////////////////////////////////////////////////////////////////////////////
+
+static unsigned int _update_fs_info();
+
+//////////////////////////////////////////////////////////////////////////////
+// The following function read a data field (from one to four bytes) 
+// from an unsigned char[] buffer, taking endianness into account. 
+// The analysed field is defined by the "offset" and "size" arguments.
+//////////////////////////////////////////////////////////////////////////////
+
+static unsigned int _read_entry( unsigned int    offset,
+                                 unsigned int    size,
+                                 unsigned char*  buffer,
+                                 unsigned int    little_indian );
+
+//////////////////////////////////////////////////////////////////////////////////
+// The following function returns the lba of first sector in DATA region 
+// from the cluster index. The cluster index must be larger than 2. 
+//////////////////////////////////////////////////////////////////////////////////
+
+static unsigned int _cluster_to_lba( unsigned int cluster );
+
+//////////////////////////////////////////////////////////////////////////////////
+// The following function returns in the "nb_entries" argument the number of files
+// (or directories) contained in a directory identidied by the "inode " pointer.
+// It returns  0 if success.
+// It returns  1 if error.
+//////////////////////////////////////////////////////////////////////////////////
+
+static unsigned int _get_nb_entries( fat_inode_t*   inode,
+                                     unsigned int*  nb_entries );
+
+//////////////////////////////////////////////////////////////////////////////////
+// The following function search in the directory identified by the "parent"
+// inode pointer a child (file or directory) identified by its "name".
+// It returns in the "inode" argument the searched child inode pointer.
+// If the searched name is not found in the Inode-Tree, the function access
+// the "file_cache" associated to the parent directory.
+// If the child exist on block device, the Inode-Tree is updated, and
+// a success code is returned.
+// If the file/dir does not exist on block device, a error code is returned.
+// It returns 0 if inode found.
+// It returns 1 if inode not found.
+// It returns 2 if error in cache access.
+//////////////////////////////////////////////////////////////////////////////////
+
+static unsigned int _get_child_from_parent( fat_inode_t*   parent,
+                                            char*          name,
+                                            fat_inode_t**  inode ); 
+
+/////////////////////////////////////////////////////////////////////////////////
+// For a file (or a directory) identified by the "pathname" argument, the
+// following function returns in the "inode" argument the inode pointer 
+// associated to the searched file (or directory), with code (0).
+// If the searched file (or directory) is not found, but the parent directory 
+// is found, it returns in the "inode" argument the pointer on the parent inode,
+// with code (1).  Finally, code (2) and code (3) are error codes.
+// Both the Inode-Tree and the involved Cache-Files are updated from the block
+// device in case of miss on one inode during the search in path.
+// Neither the Fat-Cache, nor the block device are updated.
+// It returns 0 if searched inode found
+// It returns 1 if searched inode not found but parent directory found
+// It returns 2 if searched inode not found and parent directory not found
+// It returns 3 if one name too long
+/////////////////////////////////////////////////////////////////////////////////
+
+static unsigned int _get_inode_from_path( char*          pathname,
+                                          fat_inode_t**  inode );
+
+//////////////////////////////////////////////////////////////////////////////////
+// This function computes the length and the number of LFN entries required
+// to store a node name in the "length" and "nb_lfn" arguments.
+// Short name (less than 13 characters) require 1 LFN entry.
+// Medium names (from 14 to 26 characters require 2 LFN entries.
+// Large names (up to 31 characters) require 3 LFN entries. 
+// It returns 0 if success.
+// It returns 1 if length larger than 31 characters.
+//////////////////////////////////////////////////////////////////////////////////
+
+static unsigned int _check_name_length( char* name,
+                                        unsigned int* length,
+                                        unsigned int* nb_lfn );
+
+//////////////////////////////////////////////////////////////////////////////////
+// For a node identified by the "inode" argument, this function updates the
+// "size" and "cluster" values in the entry of the parent directory File-Cache.
+// It set the dirty bit in the modified buffer of the parent directory File-Cache.
+//////////////////////////////////////////////////////////////////////////////////
+
+static unsigned int _update_dir_entry( fat_inode_t*  inode );
+
+//////////////////////////////////////////////////////////////////////////////////
+// The following function add new "child" in Cache-File of "parent" directory.
+// It access the File_Cache associated to the parent directory, and scan the
+// clusters allocated to this directory to find the NO_MORE entry.
+// This entry will be the first modified entry in the directory.
+// Regarding the name storage, it uses LFN entries for all names. 
+// Therefore, it writes 1, 2, or 3 LFN entries (depending on the child name
+// actual length, it writes one NORMAL entry, and writes the new NOMORE entry.
+// It updates the dentry field in the child inode.
+// It set the dirty bit for all modified File-Cache buffers.
+// The block device is not modified by this function.
+//////////////////////////////////////////////////////////////////////////////////
+
+static unsigned int _add_dir_entry( fat_inode_t* child,
+                                    fat_inode_t* parent );
+
+//////////////////////////////////////////////////////////////////////////////////
+// The following function invalidates all dir_entries associated to the "inode"
+// argument from its parent directory.
+// It set the dirty bit for all modified buffers in parent directory Cache-File.
+// The inode itself is not modified by this function.
+// The block device is not modified by this function.
+//////////////////////////////////////////////////////////////////////////////////
+
+static unsigned int _remove_dir_entry( fat_inode_t*  inode );
+
+//////////////////////////////////////////////////////////////////////////////////
+// The following function add the special entries "." and ".." in the File-Cache
+// of the directory identified by the "child" argument.
+// The parent directory is defined by the "parent" argument.
+// The child directory File-Cache is supposed to be empty.
+// We use two NORMAL entries for these "." and ".." entries.
+// The block device is not modified by this function.
+//////////////////////////////////////////////////////////////////////////////////
+
+static void _add_special_directories( fat_inode_t* child,
+                                      fat_inode_t* parent );
+
+//////////////////////////////////////////////////////////////////////////////////
+// The following function releases all clusters allocated to a file or directory,
+// from the cluster index defined by the "cluster" argument, until the end 
+// of the FAT linked list.
+// It calls _get_fat_entry() and _set_fat_entry() functions to scan the FAT,
+// and to update the clusters chaining.
+// The FAT region on block device is updated.
+// It returns 0 if success.
+// It returns 1 if error.
+//////////////////////////////////////////////////////////////////////////////////
+
+static unsigned int _clusters_release( unsigned int cluster );
+
+//////////////////////////////////////////////////////////////////////////////////
+// This function allocate "nb_clusters_more" new clusters to a file (or directory)
+// identified by the "inode" pointer. It allocates also the associated buffers
+// and buffer descriptors in the Cache-File.
+// It calls _get_fat_entry() and _set_fat_entry() functions to update the
+// clusters chaining in the Cache-Fat. The FAT region on block device is updated.
+// It returns 0 if success.
+// It returns 1 if error.
+//////////////////////////////////////////////////////////////////////////////////
+
+static unsigned int _clusters_allocate( fat_inode_t* inode, 
+                                        unsigned int nb_clusters_current,
+                                        unsigned int nb_clusters_more );
+
+//////////////////////////////////////////////////////////////////////////////////
+// This recursive function scan one File-Cache (or Fat-Cache) from root to leaves.
+// The cache 64-Tree infrastructure is kept, but all memory allocated for 4 Kbytes 
+// buffers, and for buffer descriptors (in leaves) is released.
+// The cache is identified by the "root" an "levels" arguments.
+// It should not contain any dirty clusters.
+// It returns 0 if success.
+// It returns 1 if error.
+//////////////////////////////////////////////////////////////////////////////////
+
+static unsigned int _release_cache_memory( fat_cache_node_t*  root,
+                                           unsigned int       levels );
+
+//////////////////////////////////////////////////////////////////////////////////
+// The following function allocates and initializes a new inode, 
+// using the values defined by the arguments.
+// If the "cache_allocate" argument is true ans empty cache is allocated.
+// The Fat-Cache is initialised as empty: all children set to NULL.
+// It returns a pointer on the new inode.
+//////////////////////////////////////////////////////////////////////////////////
+
+static fat_inode_t* _allocate_one_inode( char*        name,
+                                         unsigned int is_dir,
+                                         unsigned int cluster,
+                                         unsigned int size,
+                                         unsigned int count,
+                                         unsigned int dentry,
+                                         unsigned int cache_allocate );
+
+//////////////////////////////////////////////////////////////////////////////////
+// The following function allocates one 4 Kbytes buffer and associated cluster 
+// descriptor for the file (or directory) identified by the "inode" argument,
+// and updates the Cache_File slot identified by the "cluster_id" argument. 
+// The File-Cache slot must be empty.
+// It updates the cluster descriptor, using the "cluster" argument, that is 
+// the cluster index in FAT.  The cluster descriptor dirty field is set.
+// It traverse the 64-tree Cache-file from top to bottom to find the last level.
+//////////////////////////////////////////////////////////////////////////////////
+
+static void _allocate_one_buffer( fat_inode_t*    inode,
+                                  unsigned int    cluster_id,
+                                  unsigned int    cluster );
+
+//////////////////////////////////////////////////////////////////////////////////
+// The following function allocates one free cluster from the FAT "heap" of free 
+// clusters, and returns the cluster index in the "cluster" argument.
+// It updates the FAT slot, and the two FAT global variables: first_free_cluster,
+// and free_clusters_number.
+// It returns O if success.
+// It returns 1 if error.
+//////////////////////////////////////////////////////////////////////////////////
+
+static unsigned int _allocate_one_cluster( unsigned int*  cluster );
+
+/////////////////////////////////////////////////////////////////////////////
+// This function remove from the file system a file or a directory 
+// identified by the "inode" argument. 
+// The remove condition must be checked by the caller.
+// The relevant lock(s) must have been taken by te caller.
+// It returns O if success.
+// It returns 1 if error.
+/////////////////////////////////////////////////////////////////////////////
+
+static unsigned int _remove_node_from_fs( fat_inode_t* inode );
+
+/////////////////////////////////////////////////////////////////////////////
+// This function return the cluster index and the size for a file 
+// identified by the "pathname" argument, scanning directly the block
+// device DATA region.
+// It is intended to be called only by the _fat_load_no_cache() function, 
+// it does not use the dynamically allocated File Caches, but uses only
+// the 4 Kbytes _fat_buffer_data. 
+// It returns 0 if success.
+// It returns 1 if error.
+/////////////////////////////////////////////////////////////////////////////
+
+static unsigned int _file_info_no_cache( char*          pathname,
+                                         unsigned int*  file_cluster,
+                                         unsigned int*  file_size );
+
+/////////////////////////////////////////////////////////////////////////////
+// This function scan directly the FAT region on the block device, 
+// and returns in the "next" argument the value stored in the fat slot 
+// identified by the "cluster" argument.
+// It is intended to be called only by the _fat_load_no_cache() function,
+// as it does not use the dynamically allocated Fat-Cache, but uses only 
+// the 4 Kbytes _fat_buffer_fat.
+// It returns 0 if success.
+// It returns 1 if error.
+/////////////////////////////////////////////////////////////////////////////
+
+static unsigned int _next_cluster_no_cache( unsigned int   cluster,
+                                            unsigned int*  next );
+
+
+//////////////////////////////////////////////////////////////////////////////////
+// The following functions return the length or the size of a FAT field, 
+// identified by an (offset,length) mnemonic defined in the fat32.h file.
+//////////////////////////////////////////////////////////////////////////////////
+
+static inline int get_length( int offset , int length ) { return length; }
+
+static inline int get_offset( int offset , int length ) { return offset; }
+
+
+
+
+
+//////////////////////////////////////////////////////////////////////////////////
+//////////////////////////////////////////////////////////////////////////////////
+//                  Static functions definition
+//////////////////////////////////////////////////////////////////////////////////
+//////////////////////////////////////////////////////////////////////////////////
+
+#if GIET_DEBUG_FAT
+///////////////////////////////////////////////////
+static void _display_one_block( unsigned char* buf,
+                                char*          string,
+                                unsigned int   block_id )
+{
+    unsigned int line;
+    unsigned int word;
+
+    _printf("\n***  <%s>  block %x  ***********************************\n",
+            string , block_id );
+
+    for ( line = 0 ; line < 16 ; line++ )
+    {
+        // display line index 
+        _printf("%x : ", line );
+
+        // display 8*4 bytes hexa
+        for ( word=0 ; word<8 ; word++ )
+        {
+            unsigned int byte  = (line<<5) + (word<<2);
+            unsigned int hexa  = (buf[byte  ]<<24) |
+                                 (buf[byte+1]<<16) |
+                                 (buf[byte+2]<< 8) |
+                                 (buf[byte+3]      );
+            _printf(" %X |", hexa );
+        }
+        _printf("\n");
+    }
+    _printf("*******************************************************************\n"); 
+} // end _display_one_block()  
+#endif
+
+
+
+#if GIET_DEBUG_FAT
+/////////////////////////////////////
+static void _display_fat_descriptor()
+{
+    _printf("\n###############  FAT DESCRIPTOR  ################################"  
+            "\nFAT initialised                  %x"
+            "\nBlock Size  (bytes)              %x"
+            "\nCluster Size  (bytes)            %x"
+            "\nFAT region first lba             %x"
+            "\nFAT region size (blocks)         %x"
+            "\nDATA region first lba            %x"
+            "\nDATA region size (blocks)        %x"
+            "\nNumber of free clusters          %x"
+            "\nFirst free cluster index         %x" 
+            "\nFat_cache_levels                 %d" 
+            "\n#################################################################\n",
+            _fat.initialised,
+            _fat.sector_size,
+            _fat.cluster_size,
+            _fat.fat_lba,
+            _fat.fat_sectors,
+            _fat.data_lba,
+            _fat.data_sectors,
+            _fat.free_clusters_number,
+            _fat.first_free_cluster,
+            _fat.fat_cache_levels );
+
+} // end _display_fat_descriptor()
+#endif
+
+
+
+#if GIET_DEBUG_FAT
+////////////////////////////////////////////////////////
+static void _display_clusters_list( fat_inode_t* inode )
+{
+    _printf("\n**************** clusters for <%s> ***********************\n", inode->name );
+    unsigned int next;
+    unsigned int n       = 0;
+    unsigned int current = inode->cluster;
+    while( (current < END_OF_CHAIN_CLUSTER_MIN) && (n < 1024) )
+    {
+        _get_fat_entry( current , &next );
+        _printf(" > %X", current );
+        n++;
+        if ( (n & 0x7) == 0 ) _printf("\n");
+        current = next;
+    }
+    _printf("\n");
+}  // end _display_clusters_list()
+#endif
+
+
+
+/////////////////////////////////////////////////////////////////////////////////
+static int _fat_ioc_access( unsigned int use_irq,       // descheduling if non zero
+                            unsigned int to_mem,        // read / write
+                            unsigned int lba,           // first sector on device
+                            unsigned int buf_vaddr,     // memory buffer vaddr
+                            unsigned int count )        // number of sectors
 {
     // compute memory buffer physical address
@@ -57 +612 @@
 
     if ( ((_get_mmu_mode() & 0x4) == 0 ) || USE_IOC_RDK )  // identity
-    {
+    { 
         buf_paddr = (unsigned long long)buf_vaddr;
     }
@@ -65 +620 @@
     }
 
-#if GIET_DEBUG_FAT 
-unsigned int procid  = _get_procid();
-unsigned int x       = procid >> (Y_WIDTH + P_WIDTH);
-unsigned int y       = (procid >> P_WIDTH) & ((1<<Y_WIDTH)-1);
-unsigned int p       = procid & ((1<<P_WIDTH)-1);
-if ( _get_proctime() > GIET_DEBUG_FAT )
-_printf("\n[DEBUG FAT] P[%d,%d,%d] enters _fat_ioc_access() at cycle %d\n"
+#if (GIET_DEBUG_FAT & 1)
+if ( _get_proctime() > GIET_DEBUG_FAT )
+_printf("\n[DEBUG FAT] _fat_ioc_access() : enters at cycle %d\n"
         "  to_mem = %d / vaddr = %x / paddr = %l / sectors = %d / lba = %x\n",
-        x, y , p, _get_proctime(), to_mem, buf_vaddr, buf_paddr, count, lba );
+        _get_proctime(), to_mem, buf_vaddr, buf_paddr, count, lba );
 #endif
 
@@ -100 +651 @@
 
 
-//////////////////////////////////////////////////////////////////////////////////
-// This function displays the content of the FAT cache
-//////////////////////////////////////////////////////////////////////////////////
-#if GIET_DEBUG_FAT 
-static
-void _display_fat_cache()
-{
-    unsigned int line;
-    unsigned int word;
-    unsigned int temp[9];
-
-    temp[8] = 0;
-
-    _puts("\n*********************** fat_cache_lba = ");
-    _putx( _fat.cache_lba );
-    _puts(" *****************************\n");
-
-    for ( line = 0 ; line < 16 ; line++ )
-    {
-        // display line index 
-        _putx( line );
-        _puts(" : ");
-
-        // display 8*4 bytes hexa
-        for ( word=0 ; word<8 ; word++ )
-        {
-            unsigned int byte  = (line<<5) + (word<<2);
-            unsigned int hexa  = (_fat.fat_cache[byte  ]<<24) |
-                                 (_fat.fat_cache[byte+1]<<16) |
-                                 (_fat.fat_cache[byte+2]<< 8) |
-                                 (_fat.fat_cache[byte+3]);
-            _putx( hexa );
-            _puts(" | ");
-
-            // prepare display ascii
-            temp[word] = _fat.fat_cache[byte]         |
-                         (_fat.fat_cache[byte+1]<<8)  |
-                         (_fat.fat_cache[byte+2]<<16) |
-                         (_fat.fat_cache[byte+3]<<24) ;
-        }
-        
-        // display data ascii 
-        _puts( (char*)temp );
-        _puts("\n");
-    }
-    _puts("***************************************************************************\n");
-
-} // end _display_fat_cache()  
-#endif
-
-//////////////////////////////////////////////////////////////////////////////////
-// This function displays the FAT descriptor.
-//////////////////////////////////////////////////////////////////////////////////
-#if GIET_DEBUG_FAT
-static
-void _fat_print()
-{
-    _printf("\n########################## FAT32 ################################"  
-            "\nFAT initialised                  %x"
-            "\nSector Size  (bytes)             %x"
-            "\nSectors per cluster              %x"
-            "\nFAT region first lba             %x"
-            "\nData region first lba            %x"
-            "\nNumber of sectors for one FAT    %x"
-            "\nNumber of free clusters          %x"
-            "\nLast allocated cluster           %x" 
-            "\n#################################################################\n",
-            _fat.initialised,
-            _fat.sector_size,
-            _fat.sectors_per_cluster,
-            _fat.fat_lba,
-            _fat.data_lba,
-            _fat.fat_sectors,
-            _fat.number_free_cluster,
-            _fat.last_cluster_allocated );
-} // end _fat_print()
-#endif
-
-//////////////////////////////////////////////////////////////////////////////////
-// This function returns the length of a FAT field. This field is identified
-// by an (offset,length) mnemonic defined in fat32.h file.
-//////////////////////////////////////////////////////////////////////////////////
-static inline 
-int get_length( int offset, 
-                int length )
-{
-    return length;
+
+
+/////////////////////////////////////////////////////////////////////
+static inline unsigned int _get_levels_from_size( unsigned int size )
+{ 
+    if      ( size <= (1<<18) ) return 1;     // 64 clusters == 256 Kbytes
+    else if ( size <= (1<<24) ) return 2;     // 64 * 64 clusters => 16 Mbytes
+    else if ( size <= (1<<30) ) return 3;     // 64 * 64 * 64 cluster => 1 Gbytes
+    else                        return 4;     // 64 * 64 * 64 * 64 clusters 
 }
 
-//////////////////////////////////////////////////////////////////////////////
-// Write one 32 bits word "value" in a char[] buffer. 
-// The modified field in buffer is defined by the offset and size arguments.
-//////////////////////////////////////////////////////////////////////////////
-static 
-void _write_entry( unsigned int   offset,
-                   unsigned int   size,
-                   char*          buffer,
-                   unsigned int   value )
-{
-    unsigned int turn = 0;
-    unsigned int res  = value;
-    unsigned int mask = 0x000000ff;
-
-    while( turn != size - 1 )
-    {
-        buffer[ offset + turn ] = res & mask;
-        res = res >> 8;
-        turn++;
-    }
-    buffer[offset + turn] = res & mask;
+
+
+////////////////////////////////////////////////////////
+static unsigned int _read_entry( unsigned int    offset,
+                                 unsigned int    size,
+                                 unsigned char*  buffer,
+                                 unsigned int    little_endian )
+{
+    unsigned int n;
+    unsigned int res  = 0;
+
+    if ( little_endian)
+    {
+        for( n = size ; n > 0 ; n-- ) res = (res<<8) | buffer[offset+n-1];
+    }
+    else
+    {
+        for( n = 0 ; n < size ; n++ ) res = (res<<8) | buffer[offset+n];
+    }
+    return res;
+
+}  // end _read_entry
+
+
+
+//////////////////////////////////////////////////////////////////
+static inline unsigned int _cluster_to_lba( unsigned int cluster )       
+{
+    if ( cluster < 2 )
+    { 
+        _printf("\n[FAT ERROR] in _cluster_to_lba() cluster smaller than 2\n"); 
+        _exit();
+    }
+
+   return  ((cluster - 2) << 3) + _fat.data_lba;
 }
 
-//////////////////////////////////////////////////////////////////////////////
-// Read one 32 bits word in a char[] buffer, taking endianness into account. 
-// The analysed field in buffer is defined by the offset and size arguments.
-//////////////////////////////////////////////////////////////////////////////
-static 
-unsigned int _read_entry( unsigned int   offset,
-                          unsigned int   size,
-                          char*          buffer,
-                          unsigned int   little_indian )
-{
-    unsigned int turn;
-    unsigned int res  = 0;
-    unsigned int mask = 0x000000ff;
-
-    if( little_indian )
-    {
-        turn = size;
-        while( turn != 1 )
-        {
-            res = res | (buffer[offset + (turn-1)] & mask);
-            res = res << 8;
-            turn--;
-        }
-        res = (buffer[offset + (turn-1)] & mask) | res;
-    }
-    else
-    {
-        turn = 0;
-        while( turn != size - 1 )
-        {
-
-            res = res  | (buffer[ offset + turn ] & mask );
-            res = res << 8;
-            turn++;
-        }
-        res = res | (buffer[offset + turn] & mask);
-    }
-    return res;
-}
-
-//////////////////////////////////////////////////////////////////////////////////
-// This function retuns the cluster index from the lba of a DATA sector.
-// The lba must be larger than the lba of the first DATA sector.
-// The DATA region indexing starts a cluster 2.
-//////////////////////////////////////////////////////////////////////////////////
-static inline 
-unsigned int lba_to_cluster( unsigned int lba )                   
-{
-   if (lba < _fat.data_lba ) return 0;
-
-   return ( (lba - _fat.data_lba) / _fat.sectors_per_cluster) + 2; 
-}
-
-//////////////////////////////////////////////////////////////////////////////////
-// This function retuns the lba of first sector in DATA region 
-// from the cluster index. The cluster index must be larger than 2. 
-//////////////////////////////////////////////////////////////////////////////////
-static inline 
-unsigned int cluster_to_lba( unsigned int cluster )       
-{
-   if ( cluster < 2 ) return 0; 
-
-   return  (_fat.sectors_per_cluster * (cluster - 2)) + _fat.data_lba;
-}
-
-///////////////////////////////////////////////////////////////////////////////// 
-// This function search the FAT (using the FAT cache), and returns 
-// the next cluster index from the current cluster index in the FAT.
-// remark: a sector of FAT contains 128 cluster indexes.
-/////////////////////////////////////////////////////////////////////////////////
-static 
-unsigned int _get_next_cluster( unsigned int use_irq,
-                                unsigned int cluster )
-{
-    // compute lba of the sector containing the cluster index
-    unsigned int lba = _fat.fat_lba + (cluster / 128);
-
-    if ( lba != _fat.cache_lba )      // miss in fat_cache
-    {
-        // access fat
-        if( _fat_ioc_access( use_irq,
-                             1,               // read
-                             lba, 
-                             (unsigned int)_fat.fat_cache,
-                             1 ) )            // one sector
-        {
-            _printf("[FAT_ERROR] in get_next_cluster_id() : cannot read block %x", 
-                    lba );
-            return 1;
-        }
-        _fat.cache_lba = lba;
-    }
-
-    unsigned int next = _read_entry( ((cluster % 128) * 4), 
-                                     4, 
-                                     _fat.fat_cache,
-                                     1 );
-#if GIET_DEBUG_FAT 
-unsigned int procid  = _get_procid();
-unsigned int x       = procid >> (Y_WIDTH + P_WIDTH);
-unsigned int y       = (procid >> P_WIDTH) & ((1<<Y_WIDTH)-1);
-unsigned int p       = procid & ((1<<P_WIDTH)-1);
-if ( _get_proctime() > GIET_DEBUG_FAT )
-_printf("\n[DEBUG FAT] P[%d,%d,%d] in _get_next_cluster() :  next = %x\n",
-        x , y , p , next );
-if ( (_get_proctime() > GIET_DEBUG_FAT) && (GIET_DEBUG_FAT & 0x1) )
-_display_fat_cache();
-#endif
-
-    return next;
-}
 
 //////////////////////////////////////////////////////
-static inline unsigned char to_upper(unsigned char c)
+static inline unsigned char _to_upper(unsigned char c)
 {
    if (c >= 'a' && c <= 'z') return (c & ~(0x20));
@@ -331 +707 @@
 }
 
-////////////////////////////////////////////////////////////////
-// This function is a filter:
-// Return the c character if c is a legal short name character
-// Return the '_' character if c is illegal
-////////////////////////////////////////////////////////////////
-static 
-unsigned char illegal_short(unsigned char c)
-{
-   const unsigned char illegal_char [] =";+=[]’,\"*\\<>/?:|\0";
-   short i = 0;
-   while (illegal_char[i]!='\0')
-   {
-      if (c == illegal_char[i])
-         return '_';
-      i++;
-   }
-   return c;
-}
-
-/////////////////////////////////////////////////////////////////////////////////
-// This function test if the string argument is a legal SFN (Short File Name)
-// and copies this name (removing the .) in the sfn_string argument.
-// Criteria for a Short File Name are:
-// - separator is '.' (extension is not mandatory)
-// - 1 <= name length <= 8
-// - 0 <= extension length <= 3
-// - no illegal character (see illega_short() function)
-// Return 1 if it string is a legal SFN
-// Return 0 if not legal SFN
-/////////////////////////////////////////////////////////////////////////////////
-static 
-int is_short( char* string, 
-              char* sfn_string)
-{
-    int s_size   = 0;
-    int dot_ext  = 0;       // dot offset in the filename
-    int name_len = 0;       // length of file name
-    int ext_len  = 0;       // length of extension
-    int i        = 0;
-    int sc_i     = 0;
-    char ch;
-
-    if(string[0] == '.' && string[1] == '\0')
-    {
-        sfn_string[0] = '.';
-        return 1;
-    }
-    if(string[0] == '.' && string[1] == '.' && string[2] == '\0')
-    {
-        sfn_string[0] = '.';
-        sfn_string[1] = '.';
-        return 1;
-    }
-    sfn_string[11] = '\0';
-    while (string[s_size] != '\0')
-    {
-        if (string[s_size] == '.')
-        {
-            dot_ext = s_size;
-            ext_len = -1;
-        }
-        ext_len++;
-        s_size++;
-    }
-    if (dot_ext != 0)
-    {
-        name_len = s_size - ext_len - 1;
-    }
-    else
-    {
-        name_len = s_size;
-        ext_len = 0;
-    }
-    if ( ext_len > 3 || ( name_len > 8))
-    {
-        return 0;
-    }
-    if (dot_ext != 0)
-    {
-        while (i != ext_len)
-        {
-            ch = to_upper(string[dot_ext + 1 + i]);
-            ch = illegal_short(ch);
-            sfn_string[8+i] = ch;
-            i++;
-        } 
-    }
-    i = 0;
-    sc_i = 0;
-    while (i!= name_len)
-    {
-        ch = to_upper(string[i]);
-        ch = illegal_short(ch);
-        if (ch != '.') sfn_string[sc_i++] = ch;
-        i++;
-    }
-    return 1;
-}
-
-///////////////////////////////////////////////////////////////////////
-// This function analyses the pathname argument, from the character 
-// defined by the *nb_read argument.
-// It copies the found name (between '/') in the name[] buffer, 
-// and updates the nb_read argument.
-// Return 1 if name found, Return 0 if NUL character found, 
-///////////////////////////////////////////////////////////////////////
-static 
-int get_name_from_path( char*          pathname,
-                        char*          name,
-                        unsigned int*  nb_read )        
-{
-    if ( pathname[*nb_read] == 0 ) return 0;
-
-    int i = (pathname[*nb_read] == '/')? (*nb_read) + 1 : *nb_read;
-    int j = 0;
+
+
+///////////////////////////////////////////////////////////////////////////
+static unsigned int _get_name_from_path( char*          pathname,  // input
+                                         char*          name,      // output
+                                         unsigned int*  nb_read )  // input & output    
+{
+    // skip leading "/" character
+    if ( pathname[*nb_read] == '/' ) *nb_read = *nb_read + 1;
+
+    // initialises current indexes
+    unsigned int i = *nb_read;
+    unsigned int j = 0;
    
-    while(pathname[i] != '/' && pathname[i] != '\0')
-    {
-        name[j] = pathname[i];    
-        j++;
-        i++;
-    }
+    while ( (pathname[i] != '/') && (pathname[i] != 0) )
+    {
+        name[j++] = pathname[i++];    
+        if ( j > NAME_MAX_SIZE ) return 1;
+    }
+
+    // set end of string
     name[j] = 0;
 
+    // skip trailing "/" character
     if ( pathname[i] == '/' ) *nb_read += j+1;
     else                      *nb_read += j;
 
-    return 1;
+    return 0;
 }
 
+
+
+////////////////////////////////////////////////////////////////////
+static unsigned int _get_last_name( char*   pathname,       // input
+                                    char*   name )          // output
+{
+    unsigned int nb_read = 0;      
+    while ( pathname[nb_read] != 0 )
+    {
+        if ( _get_name_from_path( pathname, name, &nb_read ) ) return 1;
+    }
+
+    return 0;
+}   // end _get_last_name()
+
+
+
 ////////////////////////////////////////////////////////////////////////////////
-static int get_name_from_short( char* dir_entry,     // input:  SFN dir_entry
-                                char* entry_name )   // output: name
+static void _get_name_from_short( unsigned char* buffer,  // input:  SFN dir_entry
+                                  char*          name )   // output: name
 {
     unsigned int i   = 0;
@@ -470 +763 @@
     while ( i < length )
     {
-        entry_name[i] = dir_entry[i];
+        name[i] = buffer[i];
         i++;
     }
-    entry_name[i] = '\0';
-
-    return i;
+    name[i] = 0;
 }
 
 ///////////////////////////////////////////////////////////////////////////////
-static int get_name_from_long( char *dir_entry,     // input : LFN dir_entry
-                               char *entry_name )   // output : name
-{
-    unsigned int   entry_name_offset   = 0;
-    unsigned int   dir_entry_offset    = get_length(LDIR_ORD);
+static void _get_name_from_long( unsigned char*  buffer, // input : LFN dir_entry
+                                 char*           name )  // output : name
+{
+    unsigned int   name_offset         = 0;
+    unsigned int   buffer_offset       = get_length(LDIR_ORD);
     unsigned int   l_name_1            = get_length(LDIR_NAME_1);
     unsigned int   l_name_2            = get_length(LDIR_NAME_2);
@@ -495 +786 @@
     unsigned int eof          = 0;
 
-    while ( (dir_entry_offset != DIR_ENTRY_SIZE)  && (!eof) )
+    while ( (buffer_offset != DIR_ENTRY_SIZE)  && (!eof) )
     {
         while (j != l_name_1 && !eof )
         {
-            if ( (dir_entry[dir_entry_offset] == 0x00) || 
-                 (dir_entry[dir_entry_offset] == 0xFF) )
+            if ( (buffer[buffer_offset] == 0x00) || 
+                 (buffer[buffer_offset] == 0xFF) )
             {
                 eof = 1;
                 continue;
             }
-            entry_name[entry_name_offset] = dir_entry[dir_entry_offset];
-            dir_entry_offset += 2;
+            name[name_offset] = buffer[buffer_offset];
+            buffer_offset += 2;
             j += 2;
-            entry_name_offset++;
-        }
-
-        dir_entry_offset += (l_attr + l_type + l_chksum);
+            name_offset++;
+        }
+
+        buffer_offset += (l_attr + l_type + l_chksum);
         j = 0;
 
         while (j != l_name_2 && !eof )
         {
-            if ( (dir_entry[dir_entry_offset] == 0x00) || 
-                 (dir_entry[dir_entry_offset] == 0xFF) )
+            if ( (buffer[buffer_offset] == 0x00) || 
+                 (buffer[buffer_offset] == 0xFF) )
             {
                 eof = 1;
                 continue;
             }
-            entry_name[entry_name_offset] = dir_entry[dir_entry_offset];
-            dir_entry_offset += 2;
+            name[name_offset] = buffer[buffer_offset];
+            buffer_offset += 2;
             j += 2;
-            entry_name_offset++;
-        }
-
-        dir_entry_offset += l_rsvd;
+            name_offset++;
+        }
+
+        buffer_offset += l_rsvd;
         j = 0;
 
         while (j != l_name_3 && !eof )
         {
-            if ( (dir_entry[dir_entry_offset] == 0x00) || 
-                 (dir_entry[dir_entry_offset] == 0xFF) )
+            if ( (buffer[buffer_offset] == 0x00) || 
+                 (buffer[buffer_offset] == 0xFF) )
             {
                 eof = 1;
                 continue;
             }
-            entry_name[entry_name_offset] = dir_entry[dir_entry_offset];
-            dir_entry_offset += 2;
+            name[name_offset] = buffer[buffer_offset];
+            buffer_offset += 2;
             j += 2;
-            entry_name_offset++;
-        }
-    }
-    entry_name[entry_name_offset] = '\0';
-
-    return entry_name_offset;
+            name_offset++;
+        }
+    }
+    name[name_offset] = 0;
 } // end get_name_from_long()
 
-///////////////////////////////////////////////////////////////////////////////////
-// This function update a DIR_ENTRY, write a new value into a specific field 
-// (ex : DIR_FILE_SIZE, when we want update the file size after a fat_write)
-// Return 0 in case of success, > 0 if failure.
-///////////////////////////////////////////////////////////////////////////////////
-// TODO : make this function less complex
-///////////////////////////////////////////////////////////////////////////////////
-static inline 
-unsigned int _update_entry( unsigned int use_irq,
-                            unsigned int fd_id, 
-                            unsigned int field,
-                            unsigned int size,
-                            unsigned int value )
-{
-    char dir_entry[32];   // buffer to store a full directory_entry
-    char name_entry[14];  // buffer to store a 13 characters (partial) name
-    char file_name[256];  // buffer to store the name (not pathname) of the file
-
-    char sfn_string[12]  = {[0 ... 10] = ' ', '\0'};     // buffer Short File Name
-    unsigned int lba     = _fat.fd[fd_id].lba_dir_entry;  // Lba of file dir_entry
-    unsigned int is_sfn;         
-    unsigned int attr    = 0;                            // dir entry attribute
-    unsigned int ord     = 0;                            // dir entry sequence
-    unsigned int found   = 0;                            // name found
-    unsigned int offset  = 0;                            // offset in fat_cache
-    unsigned int i       = 0;
-    unsigned int nb_read = 0;
-
-    for ( i = 0 ; i < 32 ; i++ ) dir_entry[i]  = 0;
-    for ( i = 0 ; i < 14 ; i++ ) name_entry[i] = 0;
-    
-    // Get the name of the file.
-    while ( get_name_from_path( _fat.fd[fd_id].name, file_name, &nb_read ) )
-    {
-    }
-
-    // Format file_name to SFN format
-    is_sfn = is_short( file_name, sfn_string );
-
-    // access FAT
-    if ( _fat_ioc_access( use_irq,
-                          1,               // read
-                          lba, 
-                          (unsigned int)_fat.fat_cache,
-                          1 ) )            // one sector
-    {
-        _printf("\n[FAT ERROR] in _update_entry() cannot read sector %x\n", 
-                lba );
-        return 1;
-    }
-    _fat.cache_lba = lba;
-
-    // - the offset increment is an integer number of directory entry (32 bytes)
-    // - the exit condition is success (name found) or failure (end of directory) 
-    while ( !found )
-    {
-        attr = _read_entry( DIR_ATTR, _fat.fat_cache + offset, 0 );
-        ord  = _read_entry( LDIR_ORD, _fat.fat_cache + offset, 0 );
-
-        if ( is_sfn == 1 )                                     // searched name is short
-        {
-            if      ( (ord != FREE_ENTRY ) &&
-                    (ord != NO_MORE_ENTRY) &&
-                    (attr == ATTR_LONG_NAME_MASK) )    // LFN entry : skipped
+
+
+
+////////////////////////////////////////////////////////////
+static fat_inode_t* _allocate_one_inode( char*        name,
+                                         unsigned int is_dir,
+                                         unsigned int cluster,
+                                         unsigned int size, 
+                                         unsigned int count,
+                                         unsigned int dentry,
+                                         unsigned int cache_allocate )
+{
+    fat_inode_t* new_inode  = _malloc( sizeof(fat_inode_t) );
+
+    new_inode->parent   = NULL;                 // set by _add_inode_in_tree()
+    new_inode->next     = NULL;                 // set by _add_inode_in_tree()
+    new_inode->child    = NULL;                 // set by _add_inode_in_tree()
+    new_inode->cluster  = cluster;
+    new_inode->size     = size; 
+    new_inode->cache    = NULL;
+    new_inode->levels   = 0;
+    new_inode->count    = count;
+    new_inode->is_dir   = (is_dir != 0);
+    new_inode->dentry   = dentry;             
+
+    _strcpy( new_inode->name , name );  
+
+    if ( cache_allocate )
+    {
+        fat_cache_node_t* new_cache  = _malloc( sizeof(fat_cache_node_t) );
+
+        new_inode->cache    = new_cache;
+        new_inode->levels   = _get_levels_from_size( size );
+        
+        unsigned int index;
+        for ( index = 0 ; index < 64 ; index ++ )  new_cache->children[index] = NULL;
+    }
+
+    return new_inode;
+}   // end _allocate_one_inode()
+
+
+
+
+////////////////////////////////////////////////////
+static void _add_inode_in_tree( fat_inode_t*  child,
+                                fat_inode_t*  parent )
+{
+    child->parent = parent;
+    child->next   = parent->child;
+    parent->child = child;
+}   // end _add_inode-in_tree()
+
+
+
+
+//////////////////////////////////////////////////////////
+static void _remove_inode_from_tree( fat_inode_t*  inode )
+{
+    fat_inode_t*  current;
+    fat_inode_t*  prev = inode->parent->child;
+
+    if ( inode == prev )  // removed inode is first in its linked list
+    {
+        inode->parent->child = inode->next;
+    }
+    else                  // removed inode is not the first
+    {
+        for( current = prev->next ; current ; current = current->next )
+        {
+            if ( current == inode )
             {
-                offset     = offset + ((ord & 0xF) * DIR_ENTRY_SIZE);
-                continue;
+                prev->next = current->next;
             }
-            else if ( (attr != ATTR_LONG_NAME_MASK) && 
-                    (ord  != FREE_ENTRY) && 
-                    (ord  != NO_MORE_ENTRY ) )         // SFN entry : checked
+            prev = current;
+        }    
+    }    
+}  // end _delete_one_inode()
+
+
+
+
+//////////////////////////////////////////////////////////////////////
+static unsigned int _get_buffer_from_cache( fat_inode_t*        inode,
+                                            unsigned int        cluster_id,
+                                            fat_cache_desc_t**  desc )
+{
+    // get cache pointer and levels
+    fat_cache_node_t*   node;         // pointer on a 64-tree node
+    unsigned int        level;        // cache level
+
+    if ( inode == NULL )   // searched cache is the Fat-Cache
+    {
+        node   = _fat.fat_cache_root;
+        level  = _fat.fat_cache_levels;
+
+#if (GIET_DEBUG_FAT & 1)
+if ( _get_proctime() > GIET_DEBUG_FAT )
+_printf("\n[DEBUG FAT] _get_buffer_from_cache() : enters in FAT-Cache"
+        " for cluster_id = %d\n", cluster_id );
+#endif
+
+    }
+    else                   // searched cache is a File-Cache
+    {
+        node   = inode->cache;
+        level  = inode->levels;
+
+#if (GIET_DEBUG_FAT & 1)
+if ( _get_proctime() > GIET_DEBUG_FAT )
+_printf("\n[DEBUG FAT] _get_buffer_from_cache() : enters in File-Cache <%s>"
+        " for cluster_id = %d\n", inode->name , cluster_id );
+#endif
+
+    }
+
+    // search the 64-tree cache from top to bottom 
+    while ( level )
+    {
+        // compute child index at each level
+        unsigned int index = (cluster_id >> (6*(level-1))) & 0x3F;
+
+        if ( level == 1 )        // last level => children are cluster descriptors
+        {
+            fat_cache_desc_t* pdesc = (fat_cache_desc_t*)node->children[index];
+
+            if ( pdesc == NULL )      // miss 
             {
-                memcpy( dir_entry, _fat.fat_cache + offset, DIR_ENTRY_SIZE );    
+                // allocate one cluster descriptor and one 4K buffer
+                unsigned char* buf = _malloc( 4096 );
+                pdesc              = _malloc( sizeof(fat_cache_desc_t) );
+
+                // get missing cluster index lba
+                unsigned int lba;
+                unsigned int next;
+                unsigned int current = inode->cluster;
+                unsigned int count   = cluster_id;
+
+                if ( inode == NULL )      // searched cache is the Fat-Cache
+                {
+
+#if (GIET_DEBUG_FAT & 1)
+if ( _get_proctime() > GIET_DEBUG_FAT )
+_printf("\n[DEBUG FAT] _get_buffer_from_cache() : miss in FAT-Cache for cluster_id %d\n",
+        cluster_id );
+#endif
+                    lba = _fat.fat_lba + (cluster_id << 3);
+                }
+                else                      // searched cache is a File-Cache
+                {
+
+#if (GIET_DEBUG_FAT & 1)
+if ( _get_proctime() > GIET_DEBUG_FAT )
+_printf("\n[DEBUG FAT] _get_buffer_from_cache() : miss in File-Cache <%s> "
+        "for cluster_id %d\n", inode->name, cluster_id );
+#endif
+                    while ( count )
+                    { 
+                        if ( _get_fat_entry( current , &next ) ) return 1;
+                        current = next;
+                        count--;
+                    }
+                    lba = _cluster_to_lba( current );
+                }
+
+                // load one cluster (8 blocks) from block device
+                if ( _fat_ioc_access( 1,         // descheduling
+                                      1,         // to memory
+                                      lba,
+                                      (unsigned int)buf,
+                                      8 ) )
+                {
+                    _printf("\n[FAT ERROR] in _get_buffer_from_cache()"
+                            " : cannot access block device for lba = %x\n", lba );
+                    return 1;
+                }
+
+                // update cache and buffer descriptor
+                node->children[index] = pdesc;
+                pdesc->lba     = lba;
+                pdesc->buffer  = buf;
+                pdesc->dirty   = 0;
+
+#if (GIET_DEBUG_FAT & 1)
+if ( _get_proctime() > GIET_DEBUG_FAT )
+_printf("\n[DEBUG FAT] _get_buffer_from_cache() : buffer loaded from device"
+        " at vaddr = %x\n", (unsigned int)buf );
+#endif
             }
-            else if (ord == NO_MORE_ENTRY )            // end of directory : return
+
+            // return pdesc pointer
+            *desc = pdesc;
+
+            // prepare next iteration
+            level--;
+        }
+        else                      // not last level => children are 64-tree nodes
+        {
+            fat_cache_node_t* child = (fat_cache_node_t*)node->children[index];
+            if ( child == NULL )  // miss 
             {
-                _printf("\n[FAT ERROR] in _update_entry() : reaches end\n");
-                return 1;
+                // allocate a cache node if miss
+                child = (fat_cache_node_t*)_malloc( sizeof(fat_cache_node_t) );
+                node->children[index] = child;    
             }
-            else                                                                           // free entry : skipped
-            {
-                offset = offset + DIR_ENTRY_SIZE;
-                continue;
-            }
-        }
-        else                                           // searched name is long
-        {
-            if      ( (attr == ATTR_LONG_NAME_MASK) && 
-                    (ord != FREE_ENTRY) &&
-                    (ord != NO_MORE_ENTRY) )           // LFN entry : checked
-            {
-                memcpy( dir_entry, _fat.fat_cache + offset, DIR_ENTRY_SIZE );    
-            }
-            else if ( (attr != ATTR_LONG_NAME_MASK) && 
-                    (ord  != FREE_ENTRY) && 
-                    (ord  != NO_MORE_ENTRY))               // SFN entry : skipped
-            {
-                offset = offset + DIR_ENTRY_SIZE;
-                continue;
-            }
-            else if (ord == NO_MORE_ENTRY )                        // end of directory : return
-            {
-                _printf("\n[FAT ERROR] in _update_entry() reaches end\n");
-                return 1;
-            }
-            else                                       // free entry : skipped
-            {
-                offset = offset + DIR_ENTRY_SIZE;
-                continue;
-            }
-        }
-
-        // testing the name extracted from dir entry
-
-        if ( is_sfn == 1 )                             // searched name is short
-        {
-            get_name_from_short( dir_entry, name_entry );
-
-            if ( _strncmp( (char*)sfn_string, (char*)name_entry, 13 ) == 0 )
-            {
-                _write_entry(offset + field, size, _fat.fat_cache, value);
-                found = 1;
-            }
-            else                                                                       // no matching : skip
-            {
-                offset = offset + DIR_ENTRY_SIZE;
-            }
-        }
-        else                                           // searched name is long
-        {
-            get_name_from_long( dir_entry, name_entry );
-
-            unsigned shift = ((ord & 0xf) - 1) * 13;
-            if ( _strncmp( (char*)(file_name + shift), 
-                           (char*)name_entry, 13 ) == 0 )
-            {
-                if ( (ord & 0xf) == 1 )
-                {
-                    offset = offset + DIR_ENTRY_SIZE;
-                    _write_entry(offset + field, size, _fat.fat_cache, value);
-                    found = 1;
-                }
-                offset = offset + DIR_ENTRY_SIZE;
-                continue;
-            }
-            else                                                                       // no matching : skip
-            {
-                offset = offset + ((ord & 0xf) * DIR_ENTRY_SIZE) + DIR_ENTRY_SIZE;
-            }
-        }
-    }
-
-    // write block to FAT
-    if ( _fat_ioc_access( use_irq,
-                          0,                // write
-                          lba, 
-                          (unsigned int)_fat.fat_cache, 
-                          1 ) )             // one sector
-    {
-        _printf("\n[FAT ERROR] in _update_entry() cannot write sector %x\n", 
-                lba );
-        return 1;
-    }
+
+            // prepare next iteration
+            node = child;
+            level--;
+        }
+    } // end while
 
     return 0;
-} // end _update_entry()
-
-
-//////////////////////////////////////////////////////////////////////////////////
-// This function update the FS_INFO block:
-// last cluster allocated and number of free cluster. 
-// Return 0 in case of success, > 0 if failure.
-//////////////////////////////////////////////////////////////////////////////////
-static inline 
-unsigned int _update_fs_info( unsigned int use_irq )
-{
-    unsigned int lba = _fat.fs_info_lba;
-
-#if GIET_DEBUG_FAT
-if ( _get_proctime() > GIET_DEBUG_FAT )
-_printf("\n[DEBUG FAT] _update_fs_info()\n");
-#endif
-
-    // update FAT cache in case of miss
-    if ( lba != _fat.cache_lba )
-    {
-        if ( _fat_ioc_access( use_irq,
+}  // end _get_buffer_from_cache()
+
+
+
+
+/////////////////////////////////////
+static unsigned int _update_fs_info()
+{
+    // update buffer if miss
+    if ( _fat.fs_info_lba != _fat.block_buffer_lba )
+    {
+        if ( _fat_ioc_access( 1,                 // descheduling
                               1,                 // read
-                              lba, 
-                              (unsigned int)_fat.fat_cache, 
-                              1 ) )              // one sector
+                              _fat.fs_info_lba, 
+                              (unsigned int)_fat.block_buffer, 
+                              1 ) )              // one block
         {
             _printf("\n[FAT_ERROR] in _update_fs_info() cannot read block\n");
             return 1;
         }
-        _fat.cache_lba = lba;
-    }
-
-    _write_entry( FS_FREE_CLUSTER     , _fat.fat_cache, _fat.number_free_cluster );
-    _write_entry( FS_FREE_CLUSTER_HINT, _fat.fat_cache, _fat.last_cluster_allocated );
+        _fat.block_buffer_lba = _fat.fs_info_lba;
+    }
+
+    // update FAT buffer
+    unsigned int* ptr;
+    ptr  = (unsigned int*)(_fat.block_buffer + get_offset(FS_FREE_CLUSTERS) );
+    *ptr = _fat.free_clusters_number;
+
+    ptr  = (unsigned int*)(_fat.block_buffer + get_offset(FS_FREE_CLUSTER_HINT) );
+    *ptr = _fat.first_free_cluster;
    
     // write bloc to FAT
-    if ( _fat_ioc_access( use_irq,
+    if ( _fat_ioc_access( 1,                // descheduling
                           0,                // write
-                          lba,
-                          (unsigned int)_fat.fat_cache, 
-                          1 ) )             // one sector
+                          _fat.fs_info_lba,
+                          (unsigned int)_fat.block_buffer, 
+                          1 ) )             // one block
     {
         _printf("\n[FAT_ERROR] in _update_fs_info() cannot write block\n");
@@ -762 +1094 @@
     }
 
+#if (GIET_DEBUG_FAT & 1)
+if ( _get_proctime() > GIET_DEBUG_FAT )
+_printf("\n[DEBUG FAT] _update_fs_info() : nb_free = %x / first_free = %x\n",
+        _fat.free_clusters_number , _fat.first_free_cluster );
+#endif
+
     return 0;
 }  // end _update_fs_info()
 
-//////////////////////////////////////////////////////////////////////////////////
-// This function update FAT, write a new value into cluster index.
-// Used by the function _fat_allocate to update the chaining of clusters.
-// Return 0 in case of success, > 0 if failure.
-//////////////////////////////////////////////////////////////////////////////////
-static inline 
-unsigned int _update_fat( unsigned int use_irq,
-                          unsigned int cluster, 
-                          unsigned int value  )
-{
-    unsigned int lba = _fat.fat_lba + (cluster / 128);
+
+
+/////////////////////////////////////////////////////////////////
+static inline unsigned int _get_fat_entry( unsigned int  cluster,
+                                           unsigned int* value )
+{
+    // compute cluster_id & entry_id in FAT
+    // a FAT cluster is an array of 1024 unsigned int entries
+    unsigned int       cluster_id = cluster >> 10;       
+    unsigned int       entry_id   = cluster & 0x3FF;
+
+    // get pointer on the relevant cluster descriptor in FAT cache
+    fat_cache_desc_t*  pdesc;
+    unsigned int*      buffer;
+    if ( _get_buffer_from_cache( NULL,               // Fat-Cache
+                                 cluster_id,
+                                 &pdesc ) ) return 1;
+
+    // get value from FAT slot
+    buffer = (unsigned int*)pdesc->buffer;
+    *value = buffer[entry_id];
+
+    return 0;
+}  // end _get_fat_entry()
+
+
+
+////////////////////////////////////////////////////////////////
+static inline unsigned int _set_fat_entry( unsigned int cluster, 
+                                           unsigned int value  )
+{
+    // compute cluster_id & entry_id in FAT
+    // a FAT cluster is an array of 1024 unsigned int entries
+    unsigned int cluster_id = cluster >> 10;
+    unsigned int entry_id   = cluster & 0x3FF;
+
+    // get pointer on the relevant cluster descriptor in FAT cache
+    fat_cache_desc_t*  pdesc;
+    unsigned int*      buffer; 
+    if ( _get_buffer_from_cache( NULL,               // Fat-Cache
+                                 cluster_id,
+                                 &pdesc ) )  return 1;           
+
+    // set value into FAT slot
+    buffer           = (unsigned int*)pdesc->buffer;
+    buffer[entry_id] = value;
+    pdesc->dirty     = 1;
+
+    return 0;
+} // end _set_fat_entry()
+
+
+
+//////////////////////////////////////////////////////
+static void _allocate_one_buffer( fat_inode_t*  inode,
+                                  unsigned int  cluster_id,
+                                  unsigned int  cluster )
+{
+    // search the 64-tree cache from top to bottom 
+    fat_cache_node_t*  node   = inode->cache;
+    unsigned int       level  = inode->levels;
+
+    while ( level )
+    {
+        // compute child index
+        unsigned int index = (cluster_id >> (6*(level-1))) & 0x3F;
+
+        if ( level == 1 )        // last level => children are cluster descriptors
+        {
+            fat_cache_desc_t* pdesc = (fat_cache_desc_t*)node->children[index];
+            if ( pdesc != NULL )      // slot not empty!!!
+            {
+                _printf("\n[FAT ERROR] in allocate_one buffer() : slot not empty "
+                        "in File-Cache <%s> / cluster_id = %d\n", inode->name , cluster_id );
+                _exit();
+            }
+ 
+            // allocate a cluster descriptor and a 4K buffer
+            pdesc = _malloc( sizeof(fat_cache_desc_t) );
+            unsigned char* buffer = _malloc( 4096 );
+
+#if (GIET_DEBUG_FAT & 1)
+if ( _get_proctime() > GIET_DEBUG_FAT )
+_printf("\n[DEBUG FAT] _allocate_one_buffer() : buffer allocated to <%s> for cluster_id %d\n",
+        inode->name, cluster_id );
+#endif
+
+            // update cache and pdesc
+            node->children[index] = pdesc;
+            pdesc->lba     = _cluster_to_lba( cluster );
+            pdesc->buffer  = buffer;
+            pdesc->dirty   = 1;
+
+            // prepare next iteration
+            level--;
+        }
+        else                      // not last level => children are 64-tree nodes
+        {
+            fat_cache_node_t* child = (fat_cache_node_t*)node->children[index];
+            if ( child == NULL )  // miss 
+            {
+                // allocate a cache node if miss
+                child = (fat_cache_node_t*)_malloc( sizeof(fat_cache_node_t) );
+                node->children[index] = child;    
+            }
+
+            // prepare next iteration
+            node  = child;
+            level--;
+        }
+    } // end while
+} // end _allocate_one_buffer
+
+
+
+
+///////////////////////////////////////////////////////////////////
+static unsigned int _allocate_one_cluster( unsigned int*  cluster )  
+{
+    unsigned int nb_free = _fat.free_clusters_number;
+    unsigned int free    = _fat.first_free_cluster;
+
+    // scan FAT to get next free cluster index
+    unsigned int current = free;
+    unsigned int found   = 0;
+    unsigned int max     = (_fat.data_sectors >> 3);
+    unsigned int value;
+    do
+    {
+        // increment current
+        current++;
+
+        // get FAT entry indexed by current
+        if ( _get_fat_entry( current , &value ) ) return 1;
+        // test if free
+        if ( value == FREE_CLUSTER ) found = 1;
+    }
+    while ( (current < max) && (found == 0) );
+        
+    // check found  
+    if ( found == 0 )
+    {
+        _printf("\n[FAT_ERROR] in _allocate_one_cluster() : unconsistent FAT state");
+        return 1;
+    }
+
+    // update allocated FAT slot
+    if ( _set_fat_entry( free , END_OF_CHAIN_CLUSTER_MAX ) ) return 1;
+
+    // update FAT descriptor global variables
+    _fat.free_clusters_number = nb_free - 1;
+    _fat.first_free_cluster   = current;
+
+#if (GIET_DEBUG_FAT & 1)
+if ( _get_proctime() > GIET_DEBUG_FAT )
+_printf("\n[DEBUG FAT] _allocate_one_cluster() : cluster = %x / first_free = %x\n",
+        free , current );
+#endif
+
+    // returns free cluster index
+    *cluster = free;
+    return 0;
+
+}  // end _allocate_one_cluster()
+
+
+
+
+//////////////////////////////////////////////////////////////////////////
+static unsigned int _update_device_from_cache( unsigned int        levels,
+                                               fat_cache_node_t*   root,
+                                               char*               string )
+{
+    unsigned int index;
+    unsigned int ret = 0;
+
+    if ( levels == 1 )  // last level => children are cluster descriptors
+    {
+        for( index = 0 ; index < 64 ; index++ )
+        { 
+            fat_cache_desc_t* pdesc = root->children[index];
+            if ( pdesc != NULL )
+            { 
+                // update cluster on device if dirty
+                if ( pdesc->dirty )
+                {
+                    if ( _fat_ioc_access( 1,           // descheduling
+                                          0,           // to block device
+                                          pdesc->lba,
+                                          (unsigned int)pdesc->buffer,
+                                          8 ) )
+                    {
+                        _printf("\n[FAT_ERROR] in _update_device from_cache() : "
+                                " cannot access lba = %x\n", pdesc->lba );
+                        ret = 1;
+                    }
+                    else
+                    {
+                        pdesc->dirty = 0;
+
+#if (GIET_DEBUG_FAT & 1)
+if ( _get_proctime() > GIET_DEBUG_FAT )
+_printf("\n[DEBUG FAT] _update_device_from_cache() : cluster_id = %d for <%s>\n",
+        index , string );
+#endif
+
+                    }
+                }
+            }
+        }
+    }
+    else               // not the last level = recursive call on each children
+    {
+        for( index = 0 ; index < 64 ; index++ )
+        { 
+            fat_cache_node_t* pnode = root->children[index];
+            if ( pnode != NULL )
+            {
+                if ( _update_device_from_cache( levels - 1,
+                                                root->children[index],
+                                                string ) ) ret = 1;
+            }    
+        }
+    }
+    return ret;
+}  // end _update_device_from_cache()
+
+
+
+///////////////////////////////////////////////////////////////////
+static unsigned int _release_cache_memory( fat_cache_node_t*  root,
+                                           unsigned int       levels )
+{
+    unsigned int index;
+    unsigned int ret = 0;
+
+    if ( levels == 1 )  // last level => children are cluster descriptors
+    {
+        for( index = 0 ; index < 64 ; index++ )
+        { 
+            fat_cache_desc_t* pdesc = root->children[index];
+
+            if ( pdesc != NULL )
+            { 
+                // check dirty
+                if ( pdesc->dirty )
+                {
+                    _printf("\n[FAT_ERROR] in _release_cache_memory() : dirty cluster\n");
+                    ret = 1;
+                }
+                else
+                {
+                    _free( pdesc->buffer );
+                    _free( pdesc );
+                    root->children[index] = NULL;
+                }
+            }
+        }
+    }
+    else               // not the last level = recursive call on each children
+    {
+        for( index = 0 ; index < 64 ; index++ )
+        { 
+            fat_cache_node_t*    cnode = root->children[index];
+
+            if ( cnode != NULL ) ret   = _release_cache_memory( root->children[index],
+                                                                levels - 1 );
+        }
+    }
+    return ret;
+}  // end _release_cache_memory()
+
+
+
+
+
+/////////////////////////////////////////////////////////////
+static unsigned int _clusters_allocate( fat_inode_t* inode, 
+                                        unsigned int nb_current_clusters,
+                                        unsigned int nb_required_clusters )
+{
+    // Check if FAT contains enough free clusters
+    if ( nb_required_clusters > _fat.free_clusters_number )
+    {
+        _printf("\n[FAT ERROR] in _clusters_allocate() : required_clusters = %d"
+                " / free_clusters = %d\n", nb_required_clusters , _fat.free_clusters_number );
+        return 1;
+    }
+
+#if (GIET_DEBUG_FAT & 1)
+if ( _get_proctime() > GIET_DEBUG_FAT )
+_printf("\n[DEBUG FAT] _clusters_allocate() : enters for <%s> / nb_current_clusters = %d "
+        "/ nb_required_clusters = %d\n", 
+        inode->name , nb_current_clusters , nb_required_clusters );
+#endif
+ 
+    // compute last allocated cluster index when (nb_current_clusters > 0)
+    unsigned int current = inode->cluster;
+    unsigned int next;
+    unsigned int last;
+    if ( nb_current_clusters )   // clusters allocated => search last
+    {    
+        while ( current < END_OF_CHAIN_CLUSTER_MIN )
+        {
+            // get next cluster
+            if ( _get_fat_entry( current , &next ) )  return 1;
+            last    = current;
+            current = next;
+        }
+    }  
+
+    // Loop on the new clusters to be allocated
+    // if (nb_current_clusters == 0) the first new cluster index must
+    //                               be written in inode->cluster field 
+    // if (nb_current_clusters >  0) the first new cluster index must
+    //                               be written in FAT[last]
+    unsigned int      cluster_id;
+    unsigned int      new;
+    for ( cluster_id = nb_current_clusters ; 
+          cluster_id < (nb_current_clusters + nb_required_clusters) ; 
+          cluster_id ++ )
+    {
+        // allocate one cluster on block device
+        if ( _allocate_one_cluster( &new ) ) return 1;
+
+        // allocate one 4K buffer to File-Cache
+        _allocate_one_buffer( inode,
+                              cluster_id,
+                              new );
+
+        if ( cluster_id == 0 )  // update inode 
+        {
+            inode->cluster = new;
+        }
+        else                    // update FAT
+        {
+            if ( _set_fat_entry( last , new ) ) return 1;
+        }
+
+#if (GIET_DEBUG_FAT & 1)
+if ( _get_proctime() > GIET_DEBUG_FAT )
+_printf("\n[DEBUG FAT] _clusters_allocate() : done for cluster_id = %d / cluster = %x\n",
+        cluster_id , new );
+#endif
+
+        // update loop variables
+        last = new;
+
+    } // end for loop
+
+    // update FAT : last slot should contain END_OF_CHAIN_CLUSTER_MAX
+    if ( _set_fat_entry( last , END_OF_CHAIN_CLUSTER_MAX ) )  return 1;
+
+    // update the FAT on block device
+    if ( _update_device_from_cache( _fat.fat_cache_levels,
+                                    _fat.fat_cache_root,
+                                    "FAT" ) )              return 1;
+    return 0;
+}  // end _clusters_allocate()
+
+
+
+//////////////////////////////////////////////////////////////
+static unsigned int _clusters_release( unsigned int cluster )
+{
+    // scan the FAT
+    unsigned int current = cluster;
+    unsigned int next;
+    do
+    { 
+        // get next_cluster index
+        if ( _get_fat_entry( current , &next ) )  return 1;
+
+        // release current_cluster
+        if ( _set_fat_entry( current , FREE_CLUSTER ) )   return 1;
+
+        // update first_free_cluster and free_clusters_number in FAT descriptor
+        _fat.free_clusters_number = _fat.free_clusters_number + 1;
+        if ( _fat.first_free_cluster > current ) _fat.first_free_cluster = current;
+
+        // update loop variable
+        current = next;
+    }
+    while ( next < END_OF_CHAIN_CLUSTER_MIN );
+
+    // update the FAT on block device
+    if ( _update_device_from_cache( _fat.fat_cache_levels,
+                                    _fat.fat_cache_root,
+                                    "FAT" ) )                return 1;
+    return 0;
+}  // end _clusters_release()
+
+
+
+///////////////////////////////////////////////////////////
+static void _add_special_directories( fat_inode_t*  child, 
+                                      fat_inode_t*  parent )
+{
+    // get first File-Cache buffer for child
+    fat_cache_desc_t*   pdesc  = (fat_cache_desc_t*)child->cache->children[0];
+    unsigned char*      entry;
+
+    unsigned int i;
+    unsigned int cluster;
+    unsigned int size;
+
+    // set "." entry (32 bytes)
+    cluster = child->cluster;
+    size    = child->size;
+    entry   = pdesc->buffer;
+    
+    for ( i = 0 ; i < 32 ; i++ )
+    {
+        if      (i == 0 )     entry[i] = 0x2E;          // SFN
+        else if (i <  11)     entry[i] = 0x20;          // SFN
+        else if (i == 11)     entry[i] = 0x10;          // ATTR == dir
+        else if (i == 20)     entry[i] = cluster>>16;   // cluster.B2
+        else if (i == 21)     entry[i] = cluster>>24;   // cluster.B3
+        else if (i == 26)     entry[i] = cluster>>0;    // cluster.B0
+        else if (i == 27)     entry[i] = cluster>>8;    // cluster.B1
+        else if (i == 28)     entry[i] = size>>0;       // size.B0
+        else if (i == 29)     entry[i] = size>>8;       // size.B1
+        else if (i == 30)     entry[i] = size>>16;      // size.B2
+        else if (i == 31)     entry[i] = size>>24;      // size.B3
+        else                  entry[i] = 0x00;
+    }
+
+    // set ".." entry (32 bytes)
+    cluster = parent->cluster;
+    size    = parent->size;
+    entry   = pdesc->buffer + 32;
+
+    for ( i = 0 ; i < 32 ; i++ )
+    {
+        if      (i <  2 )     entry[i] = 0x2E;          // SFN
+        else if (i <  11)     entry[i] = 0x20;          // SFN
+        else if (i == 11)     entry[i] = 0x10;          // ATTR == dir
+        else if (i == 20)     entry[i] = cluster>>16;   // cluster.B2
+        else if (i == 21)     entry[i] = cluster>>24;   // cluster.B3
+        else if (i == 26)     entry[i] = cluster>>0;    // cluster.B0
+        else if (i == 27)     entry[i] = cluster>>8;    // cluster.B1
+        else if (i == 28)     entry[i] = size>>0;       // size.B0
+        else if (i == 29)     entry[i] = size>>8;       // size.B1
+        else if (i == 30)     entry[i] = size>>16;      // size.B2
+        else if (i == 31)     entry[i] = size>>24;      // size.B3
+        else                  entry[i] = 0x00;
+    }
+}  // end _add_special_directories
+
+
+
+////////////////////////////////////////////////////////////
+static unsigned int _check_name_length( char* name,
+                                        unsigned int* length,
+                                        unsigned int* nb_lfn )
+{
+    unsigned int len = _strlen( name );
+    if      ( len <= 13 )
+    {
+        *length  = len;
+        *nb_lfn  = 1;
+        return 0;
+    }
+    else if ( len <= 26 )
+    {
+        *length  = len;
+        *nb_lfn  = 2;
+        return 0;
+    }
+    else if ( len <= 31 )
+    {
+        *length  = len;
+        *nb_lfn  = 3;
+        return 0;
+    }
+    else
+    {
+        return 1;
+    }
+}  // _check_name_length()
+
+
+
+
+///////////////////////////////////////////////////////////
+static unsigned int _get_nb_entries( fat_inode_t*   inode,
+                                     unsigned int*  nb_entries )
+{
+    // scan directory until "end of directory" with two embedded loops:
+    // - scan the clusters allocated to this directory
+    // - scan the entries to find NO_MORE_ENTRY
+    fat_cache_desc_t*  pdesc;                      // pointer on buffer descriptor
+    unsigned char*     buffer;                     // 4 Kbytes buffer (one cluster)
+    unsigned int       ord;                        // ORD field in directory entry
+    unsigned int       attr;                       // ATTR field in directory entry
+    unsigned int       cluster_id = 0;             // cluster index in directory
+    unsigned int       offset     = 0;             // position in scanned buffer
+    unsigned int       found      = 0;             // NO_MORE_ENTRY found
+    unsigned int       count      = 0;             // number of valid NORMAL entries
+
+    // loop on clusters allocated to directory
+    while ( found == 0 )
+    {
+        // get one 4 Kytes buffer from File_Cache  
+        if ( _get_buffer_from_cache( inode,
+                                     cluster_id,
+                                     &pdesc ) )   return 1;
+
+        buffer = pdesc->buffer;
+        
+        // loop on directory entries in buffer
+        while ( (offset < 4096) && (found == 0) )
+        {
+            attr = _read_entry( DIR_ATTR , buffer + offset , 0 );   
+            ord  = _read_entry( LDIR_ORD , buffer + offset , 0 );
+
+            if ( ord == NO_MORE_ENTRY )
+            {
+                found = 1;
+            }  
+            else if ( ord == FREE_ENTRY )             // free entry => skip
+            {
+                offset = offset + 32;
+            }
+            else if ( attr == ATTR_LONG_NAME_MASK )   // LFN entry => skip
+            {
+                offset = offset + 32;
+            }
+            else                                      // NORMAL entry
+            {
+                count++;
+            }
+
+            offset = offset + 32;
+
+        }  // end loop on directory entries
+
+        cluster_id++;
+        offset = 0;
+
+    }  // end loop on clusters
+
+    // return nb_entries
+    *nb_entries = count;
+    
+    return 0;
+}  // end dir_not_empty()
+
+
+
+///////////////////////////////////////////////////////////
+static unsigned int _add_dir_entry( fat_inode_t*   child,
+                                    fat_inode_t*   parent )
+{
+    // get child attributes
+    unsigned int      is_dir  = child->is_dir;     
+    unsigned int      size    = child->size;
+    unsigned int      cluster = child->cluster;
+
+    // compute number of required entries to store child->name
+    // - Short name (less than 13 characters) require 3 entries: 
+    //   one LFN entry / one NORMAL entry / one NO_MORE_ENTRY entry.
+    // - Longer names (up to 31 characters) can require 4 or 5 entries:
+    //   2 or 3 LFN entries / one NORMAL entry / one NO_MORE entry.
+    unsigned int length;
+    unsigned int nb_lfn;
+    if ( _check_name_length( child->name, 
+                             &length,
+                             &nb_lfn ) )  return 1;
+
+#if (GIET_DEBUG_FAT & 1)
+if ( _get_proctime() > GIET_DEBUG_FAT )
+_printf("\n[DEBUG FAT] _add_dir_entry() : try to add <%s> in <%s> / nb_lfn = %d\n", 
+        child->name , parent->name, nb_lfn );
+#endif
+
+    // Find end of directory : two embedded loops:
+    // - scan the clusters allocated to this directory
+    // - scan the entries to find NO_MORE_ENTRY
+    fat_cache_desc_t*  pdesc;                      // pointer on buffer descriptor
+    unsigned char*     buffer;                     // 4 Kbytes buffer (one cluster)
+    unsigned int       cluster_id = 0;             // cluster index in directory
+    unsigned int       offset     = 0;             // position in scanned buffer
+    unsigned int       found      = 0;             // NO_MORE_ENTRY found
+
+    // loop on clusters allocated to directory
+    while ( found == 0 )
+    {
+        // get one 4 Kytes buffer from File_Cache  
+        if ( _get_buffer_from_cache( parent,
+                                     cluster_id,
+                                     &pdesc ) )   return 1;
+
+        buffer = pdesc->buffer;
+        
+        // loop on directory entries in buffer
+        while ( (offset < 4096) && (found == 0) )
+        {
+            if ( _read_entry( LDIR_ORD , buffer + offset , 0 ) == NO_MORE_ENTRY )
+            {
+                found        = 1;
+                pdesc->dirty = 1;
+            }  
+            else
+            {
+                offset = offset + 32;
+            }
+        }  // end loop on entries
+        if ( found == 0 )
+        {
+            cluster_id++;
+            offset = 0;
+        }
+    }  // end loop on clusters
+
+#if (GIET_DEBUG_FAT & 1)
+if ( _get_proctime() > GIET_DEBUG_FAT )
+_printf("\n[DEBUG FAT] _add_dir_entry() : get NO_MORE directory entry : "
+        " buffer = %x / offset = %x / cluster_id = %d\n",
+        (unsigned int)buffer , offset , cluster_id );
+#endif
+
+    // enter FSM :
+    // The new child requires to write 3, 4, or 5 directory entries.
+    // To actually register the new child, we use a 5 steps FSM
+    // (one state per entry to be written), that is traversed as:
+    //    LFN3 -> LFN2 -> LFN1 -> NORMAL -> NOMORE 
+    // The buffer and first directory entry to be  written are identified 
+    // by the variables : buffer / cluster_id / offset 
+
+    unsigned char* name  = (unsigned char*)child->name;
+
+    unsigned int step;          // FSM state
+
+    if      ( nb_lfn == 1 ) step = 3;
+    else if ( nb_lfn == 2 ) step = 4;
+    else if ( nb_lfn == 3 ) step = 5;
+    
+    unsigned int   i;           // byte index in 32 bytes directory
+    unsigned int   c;           // character index in name
+    unsigned char* entry;       // buffer + offset;
+
+    while ( step )   
+    {
+        // get another buffer if required
+        if ( offset >= 4096 )  // new buffer required
+        {
+            if ( cluster_id == 63 )   // we need to increase depth of File-Cache
+            {
+                _printf("\n[FAT ERROR] in add_dir_entry() File Cache depth extension "
+                        " not implemented\n" );
+                _exit();  // TODO    
+            }
+            else
+            {
+                if ( _get_buffer_from_cache( parent,
+                                             cluster_id + 1,
+                                             &pdesc ) )      return 1;        
+                buffer       = pdesc->buffer;
+                pdesc->dirty = 1;
+                offset       = 0;
+            }
+        }
+
+        // compute directory entry address
+        entry = buffer + offset;
+
+#if (GIET_DEBUG_FAT & 1)
+if ( _get_proctime() > GIET_DEBUG_FAT )
+_printf("\n[DEBUG FAT] _add_dir_entry() : FSM step = %d /"
+        " offset = %x / nb_lfn = %d\n", step, offset, nb_lfn );
+#endif
+
+        // write one 32 bytes directory entry per iteration
+        switch ( step )
+        {
+            case 5:   // write LFN3 entry
+            {
+                c = 26;
+                // scan the 32 bytes in dir_entry
+                for ( i = 0 ; i < 32 ; i++ )
+                {
+                    if (i == 0)
+                    {
+                        if ( nb_lfn == 3) entry[i] = 0x43;
+                        else              entry[i] = 0x03;
+                    }
+                    else if ( ( ((i >= 1 ) && (i<=10) && ((i&1)==1))   ||
+                                ((i >= 14) && (i<=25) && ((i&1)==0))   ||
+                                ((i >= 28) && (i<=31) && ((i&1)==0)) ) &&
+                              ( c < length ) )
+                    {
+                                          entry[i] = name[c];
+                                          c++;
+                    }
+                    else if (i == 11)     entry[i] = 0x0F;
+                    else if (i == 12)     entry[i] = 0xCA;
+                    else                  entry[i] = 0x00;
+                }
+                step--;
+                break;
+            }
+            case 4:   // write LFN2 entry  
+            {
+                c = 13;
+                // scan the 32 bytes in dir_entry
+                for ( i = 0 ; i < 32 ; i++ )
+                {
+                    if (i == 0)
+                    {
+                        if ( nb_lfn == 2) entry[i] = 0x42;
+                        else              entry[i] = 0x02;
+                    }
+                    else if ( ( ((i >= 1 ) && (i<=10) && ((i&1)==1))   ||
+                                ((i >= 14) && (i<=25) && ((i&1)==0))   ||
+                                ((i >= 28) && (i<=31) && ((i&1)==0)) ) &&
+                              ( c < length ) )
+                    {
+                                          entry[i] = name[c];
+                                          c++;
+                    }
+                    else if (i == 11)     entry[i] = 0x0F;
+                    else if (i == 12)     entry[i] = 0xCA;
+                    else                  entry[i] = 0x00;
+                }
+                step--;
+                break;
+            }
+            case 3:   // Write LFN1 entry   
+            {
+                c = 0;
+                // scan the 32 bytes in dir_entry
+                for ( i = 0 ; i < 32 ; i++ )
+                {
+                    if (i == 0)
+                    {
+                        if ( nb_lfn == 1) entry[i] = 0x41;
+                        else              entry[i] = 0x01;
+                    }
+                    else if ( ( ((i >= 1 ) && (i<=10) && ((i&1)==1))   ||
+                                ((i >= 14) && (i<=25) && ((i&1)==0))   ||
+                                ((i >= 28) && (i<=31) && ((i&1)==0)) ) &&
+                              ( c < length ) )
+                    {
+                                          entry[i] = name[c];
+                                          c++;
+                    }
+                    else if (i == 11)     entry[i] = 0x0F;
+                    else if (i == 12)     entry[i] = 0xCA;
+                    else                  entry[i] = 0x00;
+                }
+                step--;
+                break;
+            }
+            case 2:   // write NORMAL entry     
+            {
+                c = 0;
+                // scan the 32 bytes in dir_entry
+                for ( i = 0 ; i < 32 ; i++ )
+                {
+                    if      ( (i < 8) && (c < length) )             // SFN
+                    {
+                                          entry[i] = _to_upper( name[c] );
+                                          c++;
+                    }
+                    else if (i <  11)     entry[i] = 0x20;          // EXT
+                    else if (i == 11)                               // ATTR
+                    {
+                        if (is_dir)       entry[i] = 0x10;
+                        else              entry[i] = 0x20;
+                    }
+                    else if (i == 20)     entry[i] = cluster>>16;   // cluster.B2
+                    else if (i == 21)     entry[i] = cluster>>24;   // cluster.B3
+                    else if (i == 26)     entry[i] = cluster>>0;    // cluster.B0
+                    else if (i == 27)     entry[i] = cluster>>8;    // cluster.B1
+                    else if (i == 28)     entry[i] = size>>0;       // size.B0
+                    else if (i == 29)     entry[i] = size>>8;       // size.B1
+                    else if (i == 30)     entry[i] = size>>16;      // size.B2
+                    else if (i == 31)     entry[i] = size>>24;      // size.B3
+                    else                  entry[i] = 0x00;
+                }
+
+                // update the dentry field in child inode
+                child->dentry = ((cluster_id<<12) + offset)>>5;
+
+                step--;
+                break;
+            }
+            case 1:   // write NOMORE entry  
+            {
+                step--;
+                entry [0] = 0x00;
+                break;
+            }
+        } // end switch step
+        offset += 32;
+    } // exit while => exit FSM    
+
+#if (GIET_DEBUG_FAT & 1)
+if ( _get_proctime() > GIET_DEBUG_FAT )
+{
+    _printf("\n[DEBUG FAT] _add_dir_entry() : <%s> successfully added in <%s>\n",
+            child->name , parent->name );
+}
+#endif
+
+    return 0;        
+} // end _add_dir_entry
+
+
+
+////////////////////////////////////////////////////////////
+static unsigned int _remove_dir_entry( fat_inode_t*  inode )
+{
+    // compute number of LFN entries
+    unsigned int length;
+    unsigned int nb_lfn;
+    if ( _check_name_length( inode->name, 
+                             &length,
+                             &nb_lfn ) )  return 1;
+
+    // get cluster_id and offset in parent directory cache
+    unsigned int  dentry     = inode->dentry;
+    unsigned int  cluster_id = dentry >> 7;
+    unsigned int  offset     = (dentry & 0x7F)<<5;
+
+    // get buffer from parent directory cache
+    unsigned char*     buffer;
+    fat_cache_desc_t*  pdesc;
+
+    if ( _get_buffer_from_cache( inode->parent,
+                                 cluster_id,
+                                 &pdesc ) ) return 1;
+    buffer       = pdesc->buffer;
+    pdesc->dirty = 1;
+
+    // invalidate NORMAL entry in directory cache
+    buffer[offset] = 0xE5;
+
+    // invalidate LFN entries
+    while ( nb_lfn )
+    {
+        if (offset == 0)  // me must load buffer for (cluster_id - 1) 
+        {
+            if ( _get_buffer_from_cache( inode->parent,
+                                         cluster_id - 1,
+                                         &pdesc ) )   return 1;
+            buffer       = pdesc->buffer;
+            pdesc->dirty = 1;
+            offset       = 4064;
+        }
+        else
+        {
+            offset = offset - 32;
+        }
+
+        // invalidate LFN entry
+        buffer[offset] = 0xE5;
+
+        nb_lfn--;
+    }     
+         
+    return 0;
+}  // end _remove_dir_entry
+
+
+
+
+////////////////////////////////////////////////////////////
+static unsigned int _update_dir_entry( fat_inode_t*  inode )
+{  
+    // get Cache-File buffer containing the parent directory entry
+    // 128 directories entries in one 4 Kbytes buffer
+    fat_cache_desc_t*  pdesc;
+    unsigned char*     buffer;   
+    unsigned int       cluster_id = inode->dentry>>7;
+    unsigned int       offset     = (inode->dentry & 0x3F)<<5;
+
+    if ( _get_buffer_from_cache( inode->parent,
+                                 cluster_id,
+                                 &pdesc ) )    return 1;
+    buffer       = pdesc->buffer;
+    pdesc->dirty = 1;
+
+    // update size field
+    buffer[offset + 28] = inode->size>>0;       // size.B0 
+    buffer[offset + 29] = inode->size>>8;       // size.B1 
+    buffer[offset + 30] = inode->size>>16;      // size.B2 
+    buffer[offset + 31] = inode->size>>24;      // size.B3 
+
+    // update cluster field
+    buffer[offset + 26] = inode->cluster>>0;    // cluster.B0 
+    buffer[offset + 27] = inode->cluster>>8;    // cluster.B1 
+    buffer[offset + 20] = inode->cluster>>16;   // cluster.B2 
+    buffer[offset + 21] = inode->cluster>>24;   // cluster.B3 
+    
+    return 0;
+} // end _update_dir_entry()
+
+
+
+
+//////////////////////////////////////////////////////////////////
+static unsigned int _get_child_from_parent( fat_inode_t*   parent,
+                                            char*          name, 
+                                            fat_inode_t**  inode )
+{
+    fat_inode_t*   current;
+
+#if (GIET_DEBUG_FAT & 1)
+if ( _get_proctime() > GIET_DEBUG_FAT )
+_printf("\n[DEBUG FAT] _get_child_from_parent() : search <%s> in directory <%s>\n",
+        name , parent->name );
+#endif
+
+    // compute name lenth
+    unsigned int length = _strlen( name );
+    
+    // scan inodes in the parent directory 
+    for ( current = parent->child ; current ; current = current->next )
+    {
+        if ( _strncmp( name , current->name , length ) == 0 ) 
+        {
+
+#if (GIET_DEBUG_FAT & 1)
+if ( _get_proctime() > GIET_DEBUG_FAT )
+_printf("\n[DEBUG FAT] _get_child_from_parent() : found inode <%s> in directory <%s>\n", 
+        name , parent->name );
+#endif
+            *inode = current;
+            return 0;           // name found
+        }
+    }
+
+    // not found in Inode-Tree => access the parent directory 
+    // file_cache.  Two embedded loops:
+    // - scan the clusters allocated to this directory
+    // - scan the directory entries in each 4 Kbytes buffer
+
+    unsigned char*    buffer;           // pointer on one cache buffer
+    char              cname[32];        // buffer for one full entry name 
+    char              lfn1[16];         // buffer for one partial name
+    char              lfn2[16];         // buffer for one partial name
+    char              lfn3[16];         // buffer for one partial name
+    unsigned int      size;             // searched file/dir size (bytes) 
+    unsigned int      cluster;          // searched file/dir cluster index
+    unsigned int      is_dir;           // searched file/dir type
+    unsigned int      attr;             // directory entry ATTR field
+    unsigned int      ord;              // directory entry ORD field
+    unsigned int      lfn;              // LFN entries number              
+    unsigned int      dentry;           // directory entry index 
+    unsigned int      offset     = 0;   // byte offset in buffer
+    unsigned int      cluster_id = 0;   // cluster index in directory
+    int               found      = 0;   // not found (0) / name found (1) / end of dir (-1)
+
+#if (GIET_DEBUG_FAT & 1)
+if ( _get_proctime() > GIET_DEBUG_FAT )
+_printf("\n[DEBUG FAT] _get_child_from_parent() : does not found inode <%s>"
+        " in directory <%s> => search in cache\n", name , parent->name );
+#endif
+
+    // scan the clusters allocated to parent directory
+    while ( found == 0 )
+    {
+        // get one 4 Kytes buffer from parent File_Cache  
+        fat_cache_desc_t*  pdesc;
+        if ( _get_buffer_from_cache( parent,
+                                     cluster_id,
+                                     &pdesc ) )    return 2;
+        buffer = pdesc->buffer;
+
+        // scan this buffer until end of directory, end of buffer, or name found
+        while( (offset < 4096) && (found == 0) )
+        {
+
+#if (GIET_DEBUG_FAT & 1)
+if ( _get_proctime() > GIET_DEBUG_FAT )
+_printf("\n[DEBUG FAT] _get_child_from_parent() : scan buffer %d for <%s>\n",
+        cluster_id , name );
+#endif
+            attr = _read_entry( DIR_ATTR , buffer + offset , 0 );   
+            ord  = _read_entry( LDIR_ORD , buffer + offset , 0 );
+
+            if (ord == NO_MORE_ENTRY)                 // no more entry in directory => break
+            {
+                found = -1;
+            }
+            else if ( ord == FREE_ENTRY )             // free entry => skip
+            {
+                offset = offset + 32;
+            }
+            else if ( attr == ATTR_LONG_NAME_MASK )   // LFN entry => get partial name
+            {
+                unsigned int seq = ord & 0x3;
+                lfn = (seq > lfn) ? seq : lfn;   
+                if      ( seq == 1 ) _get_name_from_long( buffer + offset, lfn1 );
+                else if ( seq == 2 ) _get_name_from_long( buffer + offset, lfn2 );
+                else if ( seq == 3 ) _get_name_from_long( buffer + offset, lfn3 );
+                offset = offset + 32;
+            }
+            else                                 // NORMAL entry
+            {
+                // build the extracted name
+                if      ( lfn == 0 )
+                {
+                    _get_name_from_short( buffer + offset , cname );
+                }
+                else if ( lfn == 1 )
+                {
+                    _strcpy( cname      , lfn1 );
+                }   
+                else if ( lfn == 2 ) 
+                {
+                    _strcpy( cname      , lfn1 );
+                    _strcpy( cname + 13 , lfn2 );
+                }
+                else if ( lfn == 3 ) 
+                {
+                    _strcpy( cname      , lfn1 );
+                    _strcpy( cname + 13 , lfn2 );
+                    _strcpy( cname + 26 , lfn3 );
+                }
+                    
+                // test if extracted name == searched name
+                if ( _strncmp( name , cname , length ) == 0 )
+                {
+                    cluster = (_read_entry( DIR_FST_CLUS_HI , buffer + offset , 1 ) << 16) |
+                              (_read_entry( DIR_FST_CLUS_LO , buffer + offset , 1 )      ) ;
+                    dentry  = ((cluster_id<<12) + offset)>>5;
+                    is_dir  = ((attr & ATTR_DIRECTORY) == ATTR_DIRECTORY);
+                    size    = _read_entry( DIR_FILE_SIZE , buffer + offset , 1 );
+                    found   = 1;
+                }
+                offset = offset + 32;
+                lfn    = 0;
+            }
+        }  // end loop on directory entries
+        cluster_id++;
+        offset = 0;
+    }  // end loop on buffers
+
+    if ( found == -1 )  // found end of directory in parent directory 
+    {
+
+#if (GIET_DEBUG_FAT & 1)
+if ( _get_proctime() > GIET_DEBUG_FAT )
+_printf("\n[DEBUG FAT] _get_child_from_parent() : found end of directory in <%s>\n",
+        parent->name );
+#endif
+        *inode = NULL;
+        return 1;
+    }
+    else               // found searched name in parent directory
+    {
+        // allocate a new inode and an empty Cache-File
+        *inode = _allocate_one_inode( name,
+                                      is_dir,
+                                      cluster,
+                                      size,
+                                      0,             // count
+                                      dentry,
+                                      1 );           // cache_allocate
+
+        // introduce it in Inode-Tree
+        _add_inode_in_tree( *inode , parent );
+
+#if (GIET_DEBUG_FAT & 1)
+if ( _get_proctime() > GIET_DEBUG_FAT )
+_printf("\n[DEBUG FAT] _get_child_from_parent() : found <%s> on device\n", name );
+#endif
+        return 0;
+    }
+}  // end _get_child_from_parent()
+
+
+
+
+//////////////////////////////////////////////////////////////////
+static unsigned int _get_inode_from_path( char*          pathname,
+                                          fat_inode_t**  inode )
+{
+    char                 name[32];         // buffer for one name in pathname
+    unsigned int         nb_read;              // number of characters written in name[] 
+    fat_inode_t*         parent;           // parent inode
+    fat_inode_t*         child;            // child inode
+    unsigned int         last;             // while exit condition 
+    unsigned int         code;             // return value
+
+#if (GIET_DEBUG_FAT & 1)
+if ( _get_proctime() > GIET_DEBUG_FAT )
+_printf("\n[DEBUG FAT] _get_inode_from_path() : enters for path <%s>\n", pathname );
+#endif
+
+    // handle root directory case
+    if ( _strncmp( pathname , "/" , 2 ) == 0 )
+    {
+
+#if (GIET_DEBUG_FAT & 1)
+if ( _get_proctime() > GIET_DEBUG_FAT )
+_printf("\n[DEBUG FAT] _get_inode_from_path() : found root inode for <%s>\n", 
+        pathname );
+#endif
+        *inode  = _fat.inode_tree_root;
+        return 0;
+    }
+
+    // If the pathname is not "/", we traverse the inode tree from the root.
+    // We use _get_name_from_path() to scan pathname and extract inode names.
+    // We use _get_child_from_parent() to scan each directory in the path. 
+
+    last       = 0;
+    nb_read    = 0;                      // number of characters analysed in path
+    parent     = _fat.inode_tree_root;   // Inode-Tree root 
+    
+    while ( last == 0 )
+    {
+        // get searched file/dir name
+        if ( _get_name_from_path( pathname, name, &nb_read ) )
+        {
+            return 3;   // error : name too long
+        }
+
+        // compute last iteration condition
+        last = (pathname[nb_read] == 0);
+
+#if (GIET_DEBUG_FAT & 1)
+if ( _get_proctime() > GIET_DEBUG_FAT )
+_printf("\n[DEBUG FAT] _get_inode_from_path() : got name <%s>\n", name );
+#endif
+
+        // get child inode from parent directory
+        code = _get_child_from_parent( parent,
+                                       name,
+                                       &child );
+
+        // we  need to find the child inode for all non terminal names
+        if ( (code == 2) || ((code == 1 ) && (last == 0)) )
+        {
+
+#if (GIET_DEBUG_FAT & 1)
+if ( _get_proctime() > GIET_DEBUG_FAT )
+_printf("\n[DEBUG FAT] _get_inode_from_path() : neither parent, nor child found for <%s>\n", 
+        pathname );
+#endif
+            return 2;  // error : parent inode not found
+        }
+        
+        // update parent if not the last iteration
+        if ( last == 0 ) parent = child;
+
+    } // end while
+
+    // returns inode pointer
+    if (code == 0 )
+    {
+
+#if (GIET_DEBUG_FAT & 1)
+if ( _get_proctime() > GIET_DEBUG_FAT )
+_printf("\n[DEBUG FAT] _get_inode_from_path() : found inode for <%s>\n", 
+        pathname );
+#endif
+        *inode  = child;
+    }
+    else
+    {
+
+#if (GIET_DEBUG_FAT & 1)
+if ( _get_proctime() > GIET_DEBUG_FAT )
+_printf("\n[DEBUG FAT] _get_inode_from_path() : found only parent inode for <%s>\n",
+        pathname );
+#endif
+        *inode  = parent;
+    }
+
+    return code;                 // can be 0 (found) or 1 (not found)
+
+}  // end _get_inode_from_path() 
+
+
+
+
+//////////////////////////////////////////////////////////////
+static unsigned int _remove_node_from_fs( fat_inode_t* inode )
+{
+    // remove entry in parent directory
+    if ( _remove_dir_entry( inode ) ) return 1;
+
+    // update parent directory on device
+    if ( _update_device_from_cache( inode->parent->levels,
+                                    inode->parent->cache,
+                                    inode->parent->name ) ) return 1;
+
+    // release clusters allocated to file/dir in DATA region
+    if ( _clusters_release( inode->cluster ) ) return 1;
+
+    // release File-Cache
+    if ( _release_cache_memory( inode->cache,
+                                inode->levels ) ) return 1;
+
+    // remove inode from Inode-Tree
+    _remove_inode_from_tree( inode );
+
+    // release inode
+    _free ( inode );
+
+    return 0;
+}  // end _remove_node_from_fs()
+
+
+//////////////////////////////////////////////////////////////////
+static unsigned int _next_cluster_no_cache( unsigned int   cluster,
+                                            unsigned int*  next )
+{
+    // compute cluster_id and slot_id 
+    // each cluster contains 1024 slots (4 bytes per slot)
+    unsigned int cluster_id  = cluster >> 10;
+    unsigned int slot_id     = cluster & 0x3FF;
+
+    // compute lba of cluster identified by cluster_id
+    unsigned int lba = _fat.fat_lba + (cluster_id << 3);
+
+    // get cluster containing the adressed FAT slot in FAT buffer
+    if ( _fat_buffer_fat_lba != lba )
+    {
+        if ( _fat_ioc_access( 0,         // no descheduling
+                              1,         // read
+                              lba,
+                              (unsigned int)_fat_buffer_fat,
+                              8 ) )
+        {
+            _printf("\n[FAT ERROR] in _next_cluster_no_cache() : "
+                    "cannot load lba = %x into fat_buffer\n", lba );
+            return 1;
+        }
+
+        _fat_buffer_fat_lba = lba;
+    }
+
+    // return next cluster index
+    unsigned int* buf = (unsigned int*)_fat_buffer_fat;
+    *next = buf[slot_id];
+    return 0;
+   
+}  // end _next_cluster_no_cache()
+
+
+
+
+/////////////////////////////////////////////////////////////////
+static unsigned int _file_info_no_cache( char*          pathname,
+                                         unsigned int*  file_cluster,
+                                         unsigned int*  file_size )
+{
+    
+#if (GIET_DEBUG_FAT & 1)
+if ( _get_proctime() > GIET_DEBUG_FAT )
+_printf("\n[DEBUG FAT] _file_info_no_cache() : enters for path <%s>\n", pathname );
+#endif
+
+    char            name[32];             // buffer for one name in the analysed pathname
+    char            lfn1[16];             // buffer for a partial name in LFN entry
+    char            lfn2[16];             // buffer for a partial name in LFN entry
+    char            lfn3[16];             // buffer for a partial name in LFN entry
+    char            cname[32];            // buffer for a full name in a directory entry
+    unsigned int    nb_read;              // number of characters analysed in path 
+    unsigned int    length;               // searched name length
+    unsigned int    parent_cluster;       // cluster index for the parent directory 
+    unsigned int    child_cluster;        // cluster index for the searched file/dir
+    unsigned int    child_size;           // size of the searched file/dir
+    unsigned int    child_is_dir;         // type of the searched file/dir
+    unsigned int    offset;               // offset in a 4 Kbytes buffer
+    unsigned int    ord;                  // ORD field in a directory entry
+    unsigned int    attr;                 // ATTR field in a directory entry
+    unsigned int    lfn;                  // number of lfn entries
+    unsigned char*  buf;                  // pointer on a 4 Kbytes buffer 
+    unsigned int    found;                // name found in current directory entry
+
+    // Three embedded loops: 
+    // - scan pathname to extract file/dir names, 
+    // - for each name, scan the clusters of the parent directory
+    // - for each cluster, scan the 4 Kbytes buffer to find the file/dir name
+    // The starting point is the root directory (cluster 2)
+
+    nb_read        = 0;
+    parent_cluster = 2; 
+
+    // scan pathname  
+    while ( pathname[nb_read] != 0 )    
+    {
+        // get searched file/dir name
+        if ( _get_name_from_path( pathname, name, &nb_read ) ) return 1;
+
+#if (GIET_DEBUG_FAT & 1)
+if ( _get_proctime() > GIET_DEBUG_FAT )
+_printf("\n[DEBUG FAT] _file_info_no_cache() : search name <%s>"
+        " in cluster %x\n", name , parent_cluster );
+#endif
+        found  = 0;
+        length = _strlen( name );
+
+        // scan clusters containing the parent directory
+        while ( found == 0 )  
+        {
+            // compute lba 
+            unsigned int lba = _cluster_to_lba( parent_cluster );
+
+            // load one cluster of the parent directory into data_buffer
+            if ( _fat_buffer_data_lba != lba )
+            {
+                if ( _fat_ioc_access( 0,         // no descheduling
+                                      1,         // read
+                                      lba,
+                                      (unsigned int)_fat_buffer_data,
+                                      8 ) )
+                {
+                    _printf("\n[FAT ERROR] in _file_info_no_cache() : "
+                            "cannot load lba = %x into data_buffer\n", lba );
+                    return 1;
+                }
+
+                _fat_buffer_data_lba = lba;
+            }
+
+            offset = 0;
+
+            // scan this 4 Kbytes buffer 
+            while ( (offset < 4096) && (found == 0) )
+            {
+                buf  = _fat_buffer_data + offset;
+                attr = _read_entry( DIR_ATTR , buf , 0 );   
+                ord  = _read_entry( LDIR_ORD , buf , 0 );
+
+                if (ord == NO_MORE_ENTRY)               // no more entry => break
+                {
+                    found = 2;
+                }
+                else if ( ord == FREE_ENTRY )           // free entry => skip
+                {
+                    offset = offset + 32;
+                }
+                else if ( attr == ATTR_LONG_NAME_MASK ) // LFN entry => get partial name
+                {
+                    unsigned int seq = ord & 0x3;
+                    lfn = (seq > lfn) ? seq : lfn;   
+                    if      ( seq == 1 ) _get_name_from_long( buf, lfn1 );
+                    else if ( seq == 2 ) _get_name_from_long( buf, lfn2 );
+                    else if ( seq == 3 ) _get_name_from_long( buf, lfn3 );
+                    offset = offset + 32;
+                }
+                else                                    // NORMAL entry
+                {
+                    // build the full mame for current directory entry
+                    if      ( lfn == 0 )
+                    {
+                        _get_name_from_short( buf , cname );
+                    }
+                    else if ( lfn == 1 )
+                    {
+                        _strcpy( cname      , lfn1 );
+                    }   
+                    else if ( lfn == 2 ) 
+                    {
+                        _strcpy( cname      , lfn1 );
+                        _strcpy( cname + 13 , lfn2 );
+                    }
+                    else if ( lfn == 3 ) 
+                    {
+                        _strcpy( cname      , lfn1 );
+                        _strcpy( cname + 13 , lfn2 );
+                        _strcpy( cname + 26 , lfn3 );
+                    }
+                    
+                    // test if extracted name == searched name
+                    if ( _strncmp( name , cname , length ) == 0 )
+                    {
+                        child_cluster = (_read_entry( DIR_FST_CLUS_HI , buf , 1 ) << 16) |
+                                        (_read_entry( DIR_FST_CLUS_LO , buf , 1 )      ) ;
+                        child_is_dir  = ((attr & ATTR_DIRECTORY) == ATTR_DIRECTORY);
+                        child_size    = _read_entry( DIR_FILE_SIZE , buf , 1 );
+                        found         = 1;
+                    }
+                    offset = offset + 32;
+                    lfn = 0;
+                }
+            }  // en loop on directory entries
+            
+            // compute next cluster index
+            unsigned int next;
+            if ( _next_cluster_no_cache ( parent_cluster , &next ) ) return 1;
+            parent_cluster = next;
+        } // end loop on clusters 
+
+        if ( found == 2 )  // found end of directory => error
+        { 
+            _printf("\n[FAT ERROR] in _file_info_no_cache() : <%s> not found\n",
+                    name );
+            return 1;
+        }
+ 
+        // check type
+        if ( ((pathname[nb_read] == 0) && (child_is_dir != 0)) ||
+             ((pathname[nb_read] != 0) && (child_is_dir == 0)) )
+        {
+            _printf("\n[FAT ERROR] in _file_info_no_cache() : illegal type for <%s>\n", name );
+            return 1;
+        }
+
+        // update parent_cluster for next name
+        parent_cluster = child_cluster;
+
+    }  // end loop on names
+
+#if (GIET_DEBUG_FAT & 1)
+if ( _get_proctime() > GIET_DEBUG_FAT )
+_printf("\n[DEBUG FAT] _file_info_no_cache() : success for <%s> / "
+        "file_size = %x / file_cluster = %x\n", pathname, child_size, child_cluster );
+#endif
+
+    // return file cluster and size
+    *file_size    = child_size;
+    *file_cluster = child_cluster;
+    return 0;
+
+}  // end _file_info_no_cache()
+
+
+
+/////////////////////////////////////////////////////////////////////////////
+/////////////////////////////////////////////////////////////////////////////
+//             Extern functions                                               
+/////////////////////////////////////////////////////////////////////////////
+/////////////////////////////////////////////////////////////////////////////
+
+
+/////////////////////////////////////////////////////////////////////////////
+// This function initializes the FAT structures.
+// - The Fat-Descriptor is always initialised.
+// - The dynamically allocated structures (the Inode-Tre, the Fat_Cache, 
+//   and the File-Cache for the root directory) are only allocated
+//   and initialised if the "kernel_mode" argument is set.
+/////////////////////////////////////////////////////////////////////////////
+// Implementation note:
+// This function is called twice, by the boot-loader, and by the kernel_init.
+// It does not use dynamic memory allocation from the distributed heap.
+// It use informations found in the boot sector and FS-INFO sector.
+// that are loaded in the Fat-Descriptor temporary block_buffer.
+/////////////////////////////////////////////////////////////////////////////
+// Returns 0 if success.
+// Returns -1 if error.
+/////////////////////////////////////////////////////////////////////////////
+int _fat_init( unsigned int kernel_mode )  
+{
 
 #if GIET_DEBUG_FAT
 if ( _get_proctime() > GIET_DEBUG_FAT )
-_printf("\n[DEBUG FAT] _update_fat() : cluster = %x / value = %x\n", 
-        cluster, value );
-#endif
-
-    // update FAT cache in case of miss
-    if ( lba != _fat.cache_lba )  
-    {
-        if ( _fat_ioc_access( use_irq,
-                              1,                 // read
-                              lba, 
-                              (unsigned int)_fat.fat_cache, 
-                              1 ) )              // one sector
-        {
-            _printf("\n[FAT_ERROR] in _update_fat() cannot read block %x\n",
-                    lba );
-            return 1;
-        }
-        _fat.cache_lba = lba;
-    }
-
-    _write_entry( ((cluster % 128) << 2), 4, _fat.fat_cache, value );
-
-    // write bloc to FAT
-    if ( _fat_ioc_access( use_irq,
-                          0,                // write
-                          lba,
-                          (unsigned int)_fat.fat_cache,
-                          1 ) )             // one sector
-    {
-        _printf("\n[FAT_ERROR] in _update_fat() cannot write block %x\n",
-                lba );
-        return 1;
-    }
+_printf("\n[DEBUG FAT] _fat_init() : enters at cycle %d\n", _get_proctime() );
+#endif
+
+    // FAT initialisation should be done only once
+    if ( _fat.initialised == FAT_INITIALISED )
+    {
+        _printf("\n[FAT ERROR] in _fat_init() : FAT already initialised\n");
+        return -1;
+    }
+
+    // load Boot sector (VBR) into FAT buffer
+    if ( _fat_ioc_access( 0,                                  // no descheduling
+                          1,                                  // read
+                          0,                                  // block index
+                          (unsigned int)_fat.block_buffer,
+                          1 ) )                               // one block 
+    {
+        _printf("\n[FAT ERROR] in _fat_init() cannot load VBR\n");
+        return -1;
+    }
+
+    _fat.block_buffer_lba = 0;
+    
+#if GIET_DEBUG_FAT 
+if ( _get_proctime() > GIET_DEBUG_FAT )
+{
+    _printf("\n[DEBUG FAT] _fat_init() : Boot sector loaded\n");
+    _display_one_block( _fat.block_buffer, "block device", _fat.block_buffer_lba );
+}
+#endif
+
+    // checking various FAT32 assuptions from boot sector
+    if( _read_entry( BPB_BYTSPERSEC, _fat.block_buffer, 1 ) != 512 )
+    {
+        _printf("\n[FAT ERROR] The sector size must be 512 bytes\n");
+        return -1;
+    }
+    if( _read_entry( BPB_SECPERCLUS, _fat.block_buffer, 1 ) != 8 )
+    {
+        _printf("\n[FAT ERROR] The cluster size must be 8 blocks\n");
+        return -1;
+    }
+    if( _read_entry( BPB_NUMFATS, _fat.block_buffer, 1 ) != 1 )
+    {
+        _printf("\n[FAT ERROR] The number of FAT copies in FAT region must be 1\n");
+        return -1;
+    }
+    if( (_read_entry( BPB_FAT32_FATSZ32, _fat.block_buffer, 1 ) & 0xF) != 0 )
+    {
+        _printf("\n[FAT ERROR] The FAT region must be multiple of 16 sectors\n");
+        return -1;
+    }
+    if( _read_entry( BPB_FAT32_ROOTCLUS, _fat.block_buffer, 1 ) != 2 )
+    {
+        _printf("\n[FAT ERROR] The root directory must be at cluster 2\n");
+        return -1;
+    }
+
+    // initialise Fat-Descriptor from VBR
+    _fat.sector_size         = 512;
+    _fat.cluster_size        = 4096;
+    _fat.fat_sectors         = _read_entry( BPB_FAT32_FATSZ32 , _fat.block_buffer , 1 );
+    _fat.fat_lba             = _read_entry( BPB_RSVDSECCNT , _fat.block_buffer , 1 );
+    _fat.data_sectors        = _fat.fat_sectors << 10;
+    _fat.data_lba            = _fat.fat_lba + _fat.fat_sectors;
+    _fat.fs_info_lba         = _read_entry( BPB_FAT32_FSINFO , _fat.block_buffer , 1 );
+    _fat_buffer_fat_lba      = 0xFFFFFFFF;
+    _fat_buffer_data_lba     = 0xFFFFFFFF;
+    _fat.initialised         = FAT_INITIALISED;
+
+    // load FS_INFO sector into FAT buffer
+    if ( _fat_ioc_access( 0,                                // no descheduling 
+                          1,                                // read
+                          _fat.fs_info_lba,                 // lba 
+                          (unsigned int)_fat.block_buffer,
+                          1 ) )                             // one block
+    { 
+        _printf("\n[FAT ERROR] in _fat_init() cannot load FS_INFO Sector\n"); 
+        return -1;
+    }
+
+    _fat.block_buffer_lba = _fat.fs_info_lba;
+
+#if GIET_DEBUG_FAT
+if ( _get_proctime() > GIET_DEBUG_FAT )
+{
+    _printf("\n[DEBUG FAT] _fat_init() : FS-INFO sector loaded\n");
+    _display_one_block( _fat.block_buffer, "block device", _fat.block_buffer_lba );
+}
+#endif
+
+    // initialise Fat-Descriptor from FS_INFO
+    _fat.free_clusters_number   = _read_entry( FS_FREE_CLUSTERS    , _fat.block_buffer, 1);
+    _fat.first_free_cluster     = _read_entry( FS_FREE_CLUSTER_HINT, _fat.block_buffer, 1);
+
+    // This is done only when the _fat_init() is called in kernel mode
+
+    if ( kernel_mode )
+    {
+        unsigned int   n;
+
+        // allocate and initialise the Inode-Tree root 
+        fat_inode_t*      inode  = _malloc( sizeof(fat_inode_t) );
+        fat_cache_node_t* cache  = _malloc( sizeof(fat_cache_node_t) );
+
+        inode->parent   = NULL;        // no parent
+        inode->next     = NULL;        // no brother
+        inode->child    = NULL;        // children come later
+        inode->cache    = cache;       // empty cache
+        inode->cluster  = 2;           // forced value
+        inode->size     = 0;           // no size for a directory
+        inode->count    = 0;           // children come later
+        inode->dentry   = 0;           // no parent => no dentry
+        inode->levels   = 1;           // one level cache
+        inode->is_dir   = 1;           // it's a directory
+        _strcpy( inode->name , "/" );  
+
+        for ( n = 0 ; n < 64 ; n ++ )  cache->children[n] = NULL;
+
+        _fat.inode_tree_root = inode;
+
+        // initialise the lock
+        _spin_lock_init( &_fat.fat_lock );
+
+        // initialise File Descriptor Array
+        for( n = 0 ; n < GIET_OPEN_FILES_MAX ; n++ ) _fat.fd[n].allocated = 0;
+
+        // initialise fat_cache root
+        fat_cache_node_t*  fat_cache_root = _malloc( sizeof(fat_cache_node_t) );
+        _fat.fat_cache_root   = fat_cache_root;
+        _fat.fat_cache_levels = _get_levels_from_size( _fat.fat_sectors << 9 );
+        for ( n = 0 ; n < 64 ; n++ ) _fat.fat_cache_root->children[n] = NULL;
+
+    }  // end if kernel_mode
+
+#if GIET_DEBUG_FAT
+if ( _get_proctime() > GIET_DEBUG_FAT )
+_display_fat_descriptor();
+#endif
 
     return 0;
-} // end update_fat()
-
-//////////////////////////////////////////////////////////////////////////////////
-// This function allocate count clusters to a file by calling the
-// _update_fat function that takes care to update the chaining of clusters.
-// return 0 if success, -1 if failure
-//////////////////////////////////////////////////////////////////////////////////
-static inline 
-int _fat_allocate( unsigned int use_irq,
-                   unsigned int fd_id, 
-                   unsigned int count )
-{
-    unsigned int next_cluster = _fat.fd[fd_id].first_cluster;    // first cluster
-    unsigned int cluster_to_allocate = count;                   // to allocate
-    unsigned int last_cluster_file;                             // Last cluster 
-    unsigned int free_cluster = _fat.last_cluster_allocated + 1; // First free 
-
-    // Check if free_cluster is really free (must be true)
-    if ( _get_next_cluster( use_irq , free_cluster ) != FREE_CLUSTER)
-    {
-        _printf("\n[FAT ERROR] in _fat_allocate() : first free cluster not free\n");
-        return -1;
-    }
-    // Check if FAT contains enough cluster free for this allocation
-    if ( count > _fat.number_free_cluster )
-    {
-        _printf("\n[FAT ERROR] in _fat_allocate() : Not enough free cluster(s)\n");
-        return -1;
-    }
-
-#if GIET_DEBUG_FAT
-if ( _get_proctime() > GIET_DEBUG_FAT )
-_printf("\n[DEBUG FAT] _fat_allocate() for fd = %d\n", fd_id );
-#endif
-
-    // Get the last cluster allocated for the file (seek END_OF_CHAIN_CLUSTER).
-    do 
-    {
-        last_cluster_file = next_cluster;
-        next_cluster      = _get_next_cluster( use_irq , next_cluster );
-    }
-    while ( next_cluster < END_OF_CHAIN_CLUSTER );
-
-    // Loop on the number of clusters to be allocated
-    while ( cluster_to_allocate > 0 )
-    {
-
-#if GIET_DEBUG_FAT
-if ( _get_proctime() > GIET_DEBUG_FAT )
-_printf("\n[DEBUG FAT] cluster to update = %x / free cluster = %x / count = %d\n",
-        last_cluster_file , free_cluster , cluster_to_allocate );
-#endif
-
-        // update, in the FAT, the value of last cluster allocated by the index
-        // of free cluster.
-        if ( _update_fat( use_irq , last_cluster_file , free_cluster ) )
-        {
-            _printf("\n[FAT ERROR] in _fat_allocate() : update fat failed\n");
-            return -1;
-        }
-
-        cluster_to_allocate = cluster_to_allocate - 1;
-        // Last cluster allocated is then free_cluster
-        last_cluster_file = free_cluster;
-
-        // Last cluster to allocate done, then we must close the chain of clusters
-        if ( cluster_to_allocate == 0 )
-        {
-            // update, in the FAT, the value of the last cluster allocated by
-            // END_OF_CHAIN_CLUSTER
-            if ( _update_fat( use_irq , last_cluster_file , END_OF_CHAIN_CLUSTER ) )
-            {
-                _printf("\n[FAT ERROR] in _fat_allocate() : update fat failed\n");
-                return -1;
-            }
-        }
-
-        free_cluster = free_cluster + 1;
-
-        // Check if free_cluster is really free (must be true)
-        if ( _get_next_cluster( use_irq , free_cluster ) != FREE_CLUSTER)
-        {
-            _printf("\n[FAT ERROR] in _fat_allocate() : free_cluster not free\n");
-            return -1;
-        }
-    }
-
-    // Update field number_free_cluster and last_cluster_allocated 
-    // of structure fat for next fat_allocate
-    _fat.last_cluster_allocated = last_cluster_file;
-    _fat.number_free_cluster    = _fat.number_free_cluster - count;
-
-    if ( _update_fs_info( use_irq ) )
-    {
-        _printf("\n[FAT ERROR] in _fat_allocate() : update fs_info failed\n");
-        return -1;
-    }
-
-    return 0;
-}  // end _fat_allocate()
-
-//////////////////////////////////////////////////////////////////////////////////
-// This function read the blocks defined by the cluster index argument, in a data 
-// region containing a directory to search the name of a file/firectory. 
-// It returns the cluster index of the file/directory when the name has been found,
-// as well as the file size, and the lba.
-// We consider 3 types of directory entries:
-// - SFN : directory entry associated to a Short File Name (8.3)
-// - LFN : directory entry associated to a Long File Name
-// - XTN : directory entry containing only a name extension for a Long File Name
-// The cluster index is always stored in a SFN or LFN entry.
-// Return cluster index if name found / Return -1 if not found.
-//////////////////////////////////////////////////////////////////////////////////
-static 
-int _scan_directory( unsigned int   use_irq,         // use descheduling mode 
-                     unsigned int   cluster,         // cluster of dir_entry 
-                     char*          file_name,       // searched file/dir name
-                     unsigned int*  file_size,       // file size
-                     unsigned int*  lba_dir_entry )  // lba of dir_entry
-{
-    char dir_entry[32];       // buffer to store a full directory_entry
-    char name_entry[14];      // buffer to store a 13 characters (partial) name
-
-    char sfn_string[12]    = {[0 ... 10] = ' ', '\0'};  // buffer Short File Name
-    unsigned int  is_sfn   = is_short(file_name, sfn_string); // file_name is short
-    unsigned int  offset   = 0;                         // byte offset in block
-    unsigned int  block_id = _fat.sectors_per_cluster;  // sector index 
-    unsigned int  lba      = cluster_to_lba(cluster);   // lba of cluster 
-    unsigned int  attr     = 0;                         // dir entry attribute
-    unsigned int  ord      = 0;                         // dir entry sequence
-    unsigned int  found    = 0;                         // searched name found
-    unsigned int  long_name_found = 0;                  // matching XTN found
-    unsigned int  searched_cluster;                     // searched cluster index
+}  // end _fat_init()
+
+
+
+
+///////////////////////////////////////////////////////////////////////////////
+// This function implements the giet_fat_open() system call.
+// The semantic is similar to the UNIX open() function, but only the O_CREATE
+// and O_RDONLY flags are supported. The UNIX access rights are not supported. 
+// If the file does not exist in the specified directory, it is created.
+// If the specified directory does not exist, an error is returned.
+// It allocates a file descriptor to the calling task, for the file identified 
+// by "pathname". If several tasks try to open the same file, each task  
+// obtains a private file descriptor. 
+// A node name (file or directory) cannot be larger than 31 characters.
+///////////////////////////////////////////////////////////////////////////////
+// Returns file descriptor index if success
+// Returns a negative value if error:
+//   -1  :  "fat not initialised"
+//   -2  :  "path to parent not found"
+//   -3  :  "one name in path too long"
+//   -4  :  "file not found"
+//   -5  :  "Cannot update parent directory"
+//   -6  :  "Cannot update DATA region"
+//   -7  :  "Cannot update FAT region"
+//   -8  :  "Cannot update FS_INFO sector"
+//   -9  :  "file descriptor array full"
+///////////////////////////////////////////////////////////////////////////////
+int _fat_open( char*        pathname,     // absolute path from root
+               unsigned int flags )       // O_CREATE and O_RDONLY
+{
+    unsigned int         fd_id;            // index in File-Descriptor-Array
+    unsigned int         code;             // error code
+    fat_inode_t*         inode;            // anonymous inode pointer
+    fat_inode_t*         child;            // pointer on searched file inode
+    fat_inode_t*         parent;           // pointer on parent directory inode
+    
+    // get flags
+    unsigned int create    = ((flags & O_CREATE) != 0);
+    unsigned int read_only = ((flags & O_RDONLY) != 0); 
 
 #if GIET_DEBUG_FAT
@@ -954 +2746 @@
 unsigned int p       = procid & ((1<<P_WIDTH)-1);
 if ( _get_proctime() > GIET_DEBUG_FAT )
-_printf("\n[DEBUG FAT] _scan_directory() : P[%d,%d,%d] enters for %s\n",
-      x, y, p, file_name );
-#endif
-
-    unsigned int  i;
-    for( i = 0 ; i < 32 ; i++ ) dir_entry[i]  = 0;
-    for( i = 0 ; i < 14 ; i++ ) name_entry[i] = 0;
-
-    // load first sector from DATA region into FAT cache
-    // other sectors will be loaded inside loop as required
-    if( _fat_ioc_access( use_irq,
-                         1,               // read
-                         lba,
-                         (unsigned int)_fat.fat_cache,
-                         1 ) )            // one sector
-    {
-        _printf("[\nFAT ERROR] in _scan_directory() : cannot read sector %x\n",
-                lba );
+_printf("\n[DEBUG FAT] _fat_open() : P[%d,%d,%d] enters for path <%s> / "
+        " create = %d / read_only = %d\n",
+        x, y, p, pathname , create , read_only );
+#endif
+
+    // checking FAT initialised
+    if( _fat.initialised != FAT_INITIALISED )
+    {
+        _printf("\n[FAT ERROR] in _fat_open() : FAT not initialised\n");
         return -1;
     }
-    _fat.cache_lba = lba;
-
-#if GIET_DEBUG_FAT 
-if ( (_get_proctime() > GIET_DEBUG_FAT) && (GIET_DEBUG_FAT & 0x1) )
-_display_fat_cache();
-#endif
-
-    // in this loop we scan all names in the directory identified by cluster index 
-    // - the offset increment is an integer number of directory entry (32 bytes)
-    // - the exit condition is success (name found) or failure (end of directory) 
-    while( found == 0 )
-    {
-        // load a new sector if required
-        if (offset >= 512)              
-        {
-            if ( block_id )           // not a new cluster
-            {
-                lba += 1;
-                block_id --;
-            }
-            else                                          // get next cluster
-            {
-                cluster = _get_next_cluster( use_irq , cluster );
-
-                if ( cluster >= END_OF_CHAIN_CLUSTER  ) return END_OF_CHAIN_CLUSTER;
-
-                lba      = cluster_to_lba(cluster);
-                block_id = _fat.sectors_per_cluster;
-            }
-            if( _fat_ioc_access( use_irq,
-                                 1,               // read
-                                 lba, 
-                                 (unsigned int)_fat.fat_cache,
-                                 1 ) )            // one sector
-            {
-                _printf("\n[FAT ERROR] in _scan_directory() : cannot read sector %x\n",
-                        lba);
-                return -1;
-            }
-            _fat.cache_lba = lba;
-            block_id--;
-            offset = offset % 512;
-        }
-
-        // store the directory entry pointed by offset in dir_entry buffer,
-        // if it a possible candidate for the searched name
-
-        attr = _read_entry( DIR_ATTR, _fat.fat_cache + offset, 0);   
-        ord  = _read_entry( LDIR_ORD, _fat.fat_cache + offset, 0);
-
-        if ( is_sfn == 1 )                                // searched name is short
-        {
-            if      ( (ord != FREE_ENTRY ) &&
-                      (ord != NO_MORE_ENTRY) &&
-                      (attr == ATTR_LONG_NAME_MASK) )    // EXT entry : skipped
-            {
-                offset     = offset + ((ord & 0xF) * DIR_ENTRY_SIZE);
-            }
-            else if ( (attr != ATTR_LONG_NAME_MASK) && 
-                      (ord  != FREE_ENTRY) && 
-                      (ord  != NO_MORE_ENTRY ) )         // SFN entry : to be checked
-            {
-                memcpy( dir_entry, _fat.fat_cache + offset, DIR_ENTRY_SIZE );    
-
-                get_name_from_short( dir_entry, name_entry );
-
-                if ( _strncmp( (char*)sfn_string, 
-                               (char*)name_entry, 13 ) == 0 )  // short name found
-                {
-                    found = 1;
-                }
-                else
-                {
-                    offset = offset + DIR_ENTRY_SIZE;
-                }
-            }
-            else if (ord == NO_MORE_ENTRY )              // end of directory : return
-            {
-                return END_OF_CHAIN_CLUSTER;
-            }
-        }
-        else                                      // searched name is long
-        {
-            if( (attr == ATTR_LONG_NAME_MASK) && 
-                (ord != FREE_ENTRY) &&
-                (ord != NO_MORE_ENTRY) )                 // EXT entry : to be checked
-            {
-                memcpy( dir_entry, _fat.fat_cache + offset, DIR_ENTRY_SIZE );
-
-                get_name_from_long( dir_entry, name_entry );
-
-                unsigned shift = ((ord & 0xf) - 1) * 13;
-                if ( _strncmp( (char*)(file_name + shift), 
-                               (char*)name_entry, 13 ) == 0 )  // matching EXT
-                {
-                    if( (ord & 0xf) == 1 )                    // long name found 
-                    {
-                        long_name_found = 1;
-                    }
-                }
-                offset = offset + DIR_ENTRY_SIZE;
-            }
-            else if( (attr != ATTR_LONG_NAME_MASK) && 
-                     (ord  != FREE_ENTRY) && 
-                     (ord  != NO_MORE_ENTRY) )
-            {
-                if ( long_name_found )                   // LFN entry
-                {
-                    memcpy( dir_entry, _fat.fat_cache + offset, DIR_ENTRY_SIZE );
-                    found = 1;
-                }
-                else                                     // SFN entry: must be skipped
-                {
-                    offset = offset + DIR_ENTRY_SIZE;
-                }
-            }
-            else if (ord == NO_MORE_ENTRY )                              // end of directory : return
-            {
-                return END_OF_CHAIN_CLUSTER;
-            }
-        }
-    }  // end while
-
-    // returns cluster index
-    *file_size       = _read_entry( DIR_FILE_SIZE, dir_entry, 1 );
-    *lba_dir_entry   = lba;
-    searched_cluster = (_read_entry( DIR_FST_CLUS_HI, dir_entry, 1 ) << 16) |
-                       (_read_entry( DIR_FST_CLUS_LO, dir_entry, 1 )      ) ;
+
+    // takes the lock
+    _spin_lock_acquire( &_fat.fat_lock );
+
+    // get inode pointer
+    code = _get_inode_from_path( pathname , &inode );
+
+    if ( code == 2 )  
+    {
+        _spin_lock_release( &_fat.fat_lock );
+        _printf("\n[FAT ERROR] in _fat_open() : path to parent not found"
+                " for file <%s>\n", pathname );
+        return -2;
+    }
+    else if ( code == 3 )  
+    {
+        _spin_lock_release( &_fat.fat_lock );
+        _printf("\n[FAT ERROR] in _fat_open() : one name in path too long"
+                " for file <%s>\n", pathname );
+        return -3;
+    }
+    else if ( (code == 1) && (create == 0) )   
+    {
+        _spin_lock_release( &_fat.fat_lock );
+        _printf("\n[FAT ERROR] in _fat_open() : file not found"
+                " for file <%s>\n", pathname );
+        return -4;
+    }
+    else if ( (code == 1) && (create != 0) )   // file name not found => create 
+    {
+        // set parent inode pointer
+        parent = inode;
 
 #if GIET_DEBUG_FAT
 if ( _get_proctime() > GIET_DEBUG_FAT )
-_printf("\n[DEBUG FAT] _scan_directory() : P[%d,%d,%d] found %s"
-        " : cluster = %x\n", x, y, p, file_name, searched_cluster );
-#endif
-
-    return searched_cluster;
-} // end _scan_directory()
-
-
-//////////////////////////////////////////////////////////////////////
-// This function create a new entry in a directory identified 
-// by "dir_cluster". The name is defined by "name".
-// The type (dir/file) is defined by "is_file".
-// Returns cluster index if success, Returns -1 if error.
-//////////////////////////////////////////////////////////////////////
-static int _fat_create( char*           name,
-                        unsigned int    is_file,
-                        unsigned int    dir_cluster )
-{
-    _printf("\n[FAT ERROR] _fat_create() not implemented\n");
+_printf("\n[DEBUG FAT] _fat_open() : P[%d,%d,%d] create a new file <%s>\n",
+        x , y , p , pathname );
+#endif
+
+        // get new file name / error check already done by _get_inode_from_path()
+        char name[32];        
+        _get_last_name( pathname , name );
+
+        // allocate a new inode and an empty Cache-File 
+        child = _allocate_one_inode( name,
+                                     0,                         // not a directory
+                                     END_OF_CHAIN_CLUSTER_MAX,  // no cluster allocated
+                                     0,                         // size : new file is empty
+                                     0,                         // count incremented later
+                                     0,                         // dentry set by add_dir_entry
+                                     1 );                       // cache_allocate
+
+        // introduce inode into Inode-Tree
+        _add_inode_in_tree( child , parent );
+
+        // add an entry in the parent directory Cache_file
+        if ( _add_dir_entry( child , parent ) )
+        {
+            _spin_lock_release( &_fat.fat_lock );
+            _printf("\n[FAT ERROR] in _fat_open() : cannot update parent directory"
+                    " for file <%s>\n" , pathname );
+            return -5;
+        } 
+
+        // update DATA region on block device for parent directory
+        if ( _update_device_from_cache( parent->levels,
+                                        parent->cache,
+                                        parent->name ) )
+        {
+            _spin_lock_release( &_fat.fat_lock );
+            _printf("\n[FAT ERROR] in _fat_open() : cannot update DATA region "
+                    " for parent of file <%s>\n", pathname );
+            return -6;
+        }
+
+        // update FAT region on block device
+        if ( _update_device_from_cache( _fat.fat_cache_levels,
+                                        _fat.fat_cache_root,
+                                        "FAT" ) )
+        {
+            _spin_lock_release( &_fat.fat_lock );
+            _printf("\n[FAT ERROR] in _fat_open() : cannot update FAT region"
+                    " for file <%s>\n", pathname );
+            return -7;
+        }
+
+        // update FS_INFO sector
+        if ( _update_fs_info() )
+        {
+            _spin_lock_release( &_fat.fat_lock );
+            _printf("\n[FAT ERROR] in _fat_open() : cannot update FS-INFO"
+                    " for file <%s>\n", pathname );
+            return -8;
+        }
+    }
+    else // code == 0
+    {
+        // set searched file inode pointer
+        child = inode;
+
+#if GIET_DEBUG_FAT
+if ( _get_proctime() > GIET_DEBUG_FAT )
+_printf("\n[DEBUG FAT] _fat_open() : P[%d,%d,%d] found file <%s> on device : inode = %x\n",
+        x , y , p , pathname , child );
+#endif
+
+    }
+
+    // Search an empty slot in file descriptors array
+    fd_id = 0;
+    while ( (_fat.fd[fd_id].allocated) != 0 && (fd_id < GIET_OPEN_FILES_MAX) )
+    {
+        fd_id++;
+    }
+
+    // set file descriptor if an empty slot has been found
+    if ( fd_id < GIET_OPEN_FILES_MAX )
+    {
+        // update file descriptor
+        _fat.fd[fd_id].allocated  = 1;
+        _fat.fd[fd_id].seek       = 0;
+        _fat.fd[fd_id].read_only  = read_only;
+        _fat.fd[fd_id].inode      = child;
+
+        // increment the refcount
+        child->count = child->count + 1;
+
+        // releases the lock
+        _spin_lock_release( &_fat.fat_lock );
+
+#if GIET_DEBUG_FAT
+if ( _get_proctime() > GIET_DEBUG_FAT )
+_printf("\n[DEBUG FAT] _fat_open() : P[%d,%d,%d] got fd = %d for <%s> / "
+        "read_only = %d\n",
+        x , y , p , fd_id , pathname , read_only );
+#endif
+        return fd_id;
+    }
+    else
+    {
+        _spin_lock_release( &_fat.fat_lock );
+        _printf("\n[FAT ERROR] in _fat_open() : File-Descriptors-Array full\n");
+        return -9;
+    }
+} // end _fat_open()
+
+
+
+
+/////////////////////////////////////////////////////////////////////////////////
+// This function implements the "giet_fat_close()" system call.
+// It decrements the inode reference count, and release the fd_id entry
+// in the file descriptors array.
+// If the reference count is zero, it writes all dirty clusters on block device, 
+// and releases the memory allocated to the file_cache: The cache 64-Tree
+// infrastructure (depending on file size) is kept, but all buffers and all
+// buffer descriptors are released.
+/////////////////////////////////////////////////////////////////////////////////
+// Returns 0 on success.
+// Returns negative value if error:
+//  -1  : "FAT not initialised"
+//  -2  : "Illegal file descriptor"
+//  -3  : "Cannot update DATA region for closed file"
+//  -4  : "Cannot release memory"
+/////////////////////////////////////////////////////////////////////////////////
+int _fat_close( unsigned int fd_id )
+{
+    // checking FAT initialised
+    if( _fat.initialised != FAT_INITIALISED )
+    {
+        _printf("\n[FAT ERROR] in _fat_close() : FAT not initialised\n");
+        return -1;
+    }
+
+    if( (fd_id >= GIET_OPEN_FILES_MAX) )
+    {
+        _printf("\n[FAT ERROR] in _fat_close() : illegal file descriptor index\n");
+        return -2;
+    } 
+
+    // takes lock
+    _spin_lock_acquire( &_fat.fat_lock );
+
+    // get the inode pointer 
+    fat_inode_t*  inode = _fat.fd[fd_id].inode;
+
+    // decrement reference count
+    inode->count = inode->count - 1;
+    
+#if GIET_DEBUG_FAT
+if ( _get_proctime() > GIET_DEBUG_FAT )
+_printf("\n[FAT DEBUG] _fat_close() for file <%s> : refcount = %d\n",
+        inode->name , inode->count );
+#endif
+
+    // update block device and release File-Cache if no more references
+    if ( inode->count == 0 )
+    {
+        // update all dirty clusters for closed file
+        if ( _update_device_from_cache( inode->levels, 
+                                        inode->cache,
+                                        inode->name ) ) 
+        {
+            _spin_lock_release( &_fat.fat_lock );
+            _printf("\n[FAT ERROR] in _fat_close() : cannot write dirty clusters "
+                    "for file <%s>\n", inode->name );
+            return -3;
+        }
+
+#if GIET_DEBUG_FAT
+if ( _get_proctime() > GIET_DEBUG_FAT )
+_printf("\n[FAT DEBUG] _fat_close() update device for file <%s>\n", inode->name );
+#endif
+
+        // update directory dirty clusters for parent directory
+        if ( _update_device_from_cache( inode->parent->levels, 
+                                        inode->parent->cache,
+                                        inode->parent->name ) ) 
+        {
+            _spin_lock_release( &_fat.fat_lock );
+            _printf("\n[FAT ERROR] in _fat_close() : cannot write dirty clusters "
+                    "for directory <%s>\n", inode->parent->name );
+            return -4;
+        }
+
+#if GIET_DEBUG_FAT
+if ( _get_proctime() > GIET_DEBUG_FAT )
+_printf("\n[FAT DEBUG] _fat_close() update device for parent directory <%s>\n",
+        inode->parent->name );
+#endif
+
+        // release memory allocated to File-Cache
+        if ( _release_cache_memory( inode->cache,
+                                    inode-> levels ) )
+        {
+            _spin_lock_release( &_fat.fat_lock );
+            _printf("\n[FAT ERROR] in _fat_close() : cannot release cache memory "
+                    "for file <%s>\n", _fat.fd[fd_id].inode->name );
+            return -5;
+        }
+
+#if GIET_DEBUG_FAT
+if ( _get_proctime() > GIET_DEBUG_FAT )
+_printf("\n[FAT DEBUG] _fat_close() release memory for File-Cache <%s>\n",
+        inode->name );
+#endif
+
+    }
+
+    // release fd_id entry in file descriptor array
+    _fat.fd[fd_id].allocated = 0;
+
+    // release lock
+    _spin_lock_release( &_fat.fat_lock );
+
     return 0;
-}  //end _fat_create()
-
-
-
-////////////// Extern functions //////////////////////////////////////////
-
-//////////////////////////////////////////////////////////////////////////
-// This function initializes the FAT structure, including the open
-// files descriptors array and the lock protecting the FAT,
-// from informations found in the boot record.
-// This should be done only once.
-//////////////////////////////////////////////////////////////////////////
-// Return 0 if success, exit if failure 
-//////////////////////////////////////////////////////////////////////////
-int _fat_init( unsigned int use_irq )  
-{
+} // end fat_close()
+
+
+
+
+/////////////////////////////////////////////////////////////////////////////////
+// This function implements the giet_fat_file_info() system call.
+// It returns the size and the current offset value for a file identified 
+// by the "fd_id" argument. 
+/////////////////////////////////////////////////////////////////////////////////
+// Returns  0 if success.
+// Returns negative value if error.
+//  -1  : "FAT not initialised"
+//  -2  : "Illegal file descriptor"
+//  -3  : "File not open"
+/////////////////////////////////////////////////////////////////////////////////
+int _fat_file_info( unsigned int   fd_id,
+                    unsigned int*  size,
+                    unsigned int*  offset )
+{
+    // checking FAT initialised
+    if( _fat.initialised != FAT_INITIALISED )
+    {
+        _printf("\n[FAT ERROR] in _fat_file_info() : FAT not initialised\n");
+        return -1;
+    }
+
+
+    if( fd_id >= GIET_OPEN_FILES_MAX )
+    {
+        _printf("\n[FAT ERROR] in _fat_file_info() : illegal file descriptor index\n");
+        return -2;
+    } 
+
+    if ( _fat.fd[fd_id].allocated == 0 )
+    {
+        _printf("\n[FAT ERROR] in _fat_file_info() : file <%s> not open\n",
+                _fat.fd[fd_id].inode->name );
+        return -3;
+    }
+
+    *size   = _fat.fd[fd_id].inode->size;
+    *offset = _fat.fd[fd_id].seek;  
+    return 0;
+
+} // end _fat_file_info()
+
+
+
+
+/////////////////////////////////////////////////////////////////////////////////
+// The following function implements the "giet_fat_read()" system call.
+// It transfers "count" bytes from the File_Cache associated to the file
+// identified by "fd_id", to the user "buffer", from the current file offset.
+// It has the same semantic as the UNIX "read()" function.
+// In case of miss in the File_Cache, it loads all involved clusters into cache.
+/////////////////////////////////////////////////////////////////////////////////
+// Returns number of bytes actually transfered if success .
+// Returns 0 if EOF encountered (offset + count > file_size). 
+// Returns a negative value if error:
+//   -1 :  "fat not initialised"
+//   -2 :  "file not open"
+//   -3 :  "cannot load file from device"
+/////////////////////////////////////////////////////////////////////////////////
+int _fat_read( unsigned int fd_id,     // file descriptor index
+               void*        buffer,    // destination buffer
+               unsigned int count )    // number of bytes to read
+{
+    // checking FAT initialised
+    if( _fat.initialised != FAT_INITIALISED )
+    {
+        _printf("\n[FAT ERROR] in _fat_write() : FAT not initialised\n");
+        return -1;
+    }
+
+    // check fd_id overflow
+    if ( fd_id >= GIET_OPEN_FILES_MAX )
+    {
+        _printf("\n[FAT ERROR] in _fat_read() : illegal file descriptor\n");
+        return -1;
+    }
+
+    // check file is open
+    if ( _fat.fd[fd_id].allocated == 0 )
+    {
+        _printf("\n[FAT ERROR] in _fat_read() : file not open\n");
+        return -2;
+    }
+
+    // takes lock
+    _spin_lock_acquire( &_fat.fat_lock );
+           
+    // get file inode pointer and offset
+    fat_inode_t* inode  = _fat.fd[fd_id].inode;
+    unsigned int seek   = _fat.fd[fd_id].seek;
+
+    // check count & seek versus file size
+    if ( count + seek > inode->size )
+    {
+        _spin_lock_release( &_fat.fat_lock );
+        _printf("\n[FAT ERROR] in _fat_read() : file too small"
+                " / seek = %x / count = %x / file_size = %x\n",
+                seek , count , inode->size );
+        return 0;
+    }
+
+    // compute first_cluster_id and first_byte_to_move 
+    unsigned int first_cluster_id   = seek >> 12;
+    unsigned int first_byte_to_move = seek & 0xFFF;   
+
+    // compute last_cluster and last_byte_to_move 
+    unsigned int last_cluster_id   = (seek + count - 1) >> 12;   
+    unsigned int last_byte_to_move = (seek + count - 1) & 0xFFF;
 
 #if GIET_DEBUG_FAT
@@ -1148 +3133 @@
 unsigned int p       = procid & ((1<<P_WIDTH)-1);
 if ( _get_proctime() > GIET_DEBUG_FAT )
-_printf("\n[DEBUG FAT] P[%d,%d,%d] enters _fat_init\n",x,y,p);
-#endif
-
-    // FAT initialisation should be done only once
-    if ( _fat.initialised == FAT_INITIALISED )
-    {
-        _printf("\n[FAT ERROR] Strange, FAT already initialised...\n");
-        _exit();
-    }
-
-    // load Boot Record (VBR) into fat cache
-    if ( _fat_ioc_access( use_irq,
-                          1,                   // read
-                          0,                   // sector index
-                          (unsigned int)_fat.fat_cache,
-                          1 ) )                // one sector
-    {
-        _printf("\n[FAT ERROR] in _fat_init() cannot load VBR\n");
-        _exit();
-    }
-    _fat.cache_lba = 0;
-
-#if GIET_DEBUG_FAT > 1
-if ( _get_proctime() > GIET_DEBUG_FAT )
-_printf("\n[DEBUG FAT] _fat_init() : Boot Sector Loaded\n");
-if ( (_get_proctime() > GIET_DEBUG_FAT) && (GIET_DEBUG_FAT & 0x1) )
-_display_fat_cache();
-#endif
-
-    // checking various FAT32 assuptions from boot sector
-    if( _read_entry( BPB_BYTSPERSEC, _fat.fat_cache, 1 ) != 512 )
-    {
-        _printf("\n[FAT ERROR] The sector size must be 512 bytes\n");
-        _exit();
-    }
-    if( _read_entry( BPB_NUMFATS, _fat.fat_cache, 1 ) != 1 )
-    {
-        _printf("\n[FAT ERROR] The number of FAT copies in FAT region must be 1\n");
-        _exit();
-    }
-    if( (_read_entry( BPB_FAT32_FATSZ32, _fat.fat_cache, 1 ) & 0xF) != 0 )
-    {
-        _printf("\n[FAT ERROR] The FAT region must be multiple of 32 sectors\n");
-        _exit();
-    }
-    if( _read_entry( BPB_FAT32_ROOTCLUS, _fat.fat_cache, 1 ) != 2 )
-    {
-        _printf("\n[FAT ERROR] The first cluster index must be 2\n");
-        _exit();
-    }
-    // FS Info always in sector 1
-    _fat.fs_info_lba         = _read_entry( BPB_FAT32_FSINFO, _fat.fat_cache, 1 );
-
-    // initialise fat descriptor from VBR
-    _fat.sectors_per_cluster = _read_entry( BPB_SECPERCLUS, _fat.fat_cache, 1 );
-    _fat.sector_size         = _read_entry( BPB_BYTSPERSEC, _fat.fat_cache, 1 );
-    _fat.cluster_size        = _fat.sectors_per_cluster * 512;
-    _fat.fat_sectors         = _read_entry( BPB_FAT32_FATSZ32, _fat.fat_cache, 1 );
-    _fat.fat_lba             = _read_entry( BPB_RSVDSECCNT, _fat.fat_cache, 1 );
-    _fat.data_lba            = _fat.fat_lba + _fat.fat_sectors;
-    _fat.initialised         = FAT_INITIALISED;
-
-    // initalise the lock protecting the FAT
-    _spin_lock_init( &_fat.fat_lock );
-
-    // initialise file descriptor array
-    unsigned int   n;
-    for( n = 0 ; n < GIET_OPEN_FILES_MAX ; n++ ) _fat.fd[n].used = 0;
+_printf("\n[DEBUG FAT] _fat_read() : P[%d,%d,%d] enters for file <%s> "
+        " / bytes = %x / offset = %x\n"
+        "first_cluster_id = %x / first_byte_to_move = %x"
+        " / last_cluster_id = %x / last_byte_to_move = %x\n",
+        x , y , p , inode->name , count , seek ,
+        first_cluster_id , first_byte_to_move , last_cluster_id , last_byte_to_move );
+#endif
+
+    // loop on all cluster covering the requested transfer
+    unsigned int cluster_id;
+    unsigned int done = 0;
+    for ( cluster_id = first_cluster_id ; cluster_id <= last_cluster_id ; cluster_id++ )
+    {
+        // get pointer on the cluster_id buffer in cache 
+        unsigned char*     cbuf;
+        fat_cache_desc_t*  pdesc;
+        if ( _get_buffer_from_cache( inode, 
+                                     cluster_id,
+                                     &pdesc ) )
+        {
+            _spin_lock_release( &_fat.fat_lock );
+            _printf("\n[FAT ERROR] in _fat_read() : cannot load file <%s>\n",
+                    inode->name );
+            return -3;
+        }
+        cbuf = pdesc->buffer;
 
 #if GIET_DEBUG_FAT
 if ( _get_proctime() > GIET_DEBUG_FAT )
-_printf("\n[DEBUG FAT] _fat_init() : FS_INFO Sector = %x\n", _fat.fs_info_lba );
-#endif
-
-    // load FS_INFO into fat cache
-    if ( _fat_ioc_access( use_irq,
-                          1,                  // read
-                          _fat.fs_info_lba,    
-                          (unsigned int)_fat.fat_cache,
-                          1 ) )               // one sector
-    { 
-        _printf("\n[FAT ERROR] in _fat_init() cannot load FS_INFO Sector\n"); 
-        _exit();
-    }
-    _fat.cache_lba = _fat.fs_info_lba;
-
-    _fat.number_free_cluster    = _read_entry( FS_FREE_CLUSTER     , _fat.fat_cache, 1);
-    _fat.last_cluster_allocated = _read_entry( FS_FREE_CLUSTER_HINT, _fat.fat_cache, 1);
+_printf("\n[DEBUG FAT] _fat_read() : P[%d,%d,%d] moves cluster_id %d from Cache-File <%s>\n",
+        x , y , p , cluster_id, inode->name );
+#endif
+
+        // compute memcpy arguments
+        unsigned char*  source;
+        unsigned int    nbytes;
+        unsigned char*  dest = (unsigned char*)buffer + done;
+        if ( (cluster_id == first_cluster_id) && (cluster_id == last_cluster_id) )
+        {
+            source = cbuf + first_byte_to_move; 
+            nbytes = last_byte_to_move - first_byte_to_move + 1;
+        }
+        else if ( cluster_id == first_cluster_id )
+        {
+            source = cbuf + first_byte_to_move; 
+            nbytes = 4096 - first_byte_to_move;
+        }
+        else if ( cluster_id == last_cluster_id )
+        {
+            source = cbuf; 
+            nbytes = last_byte_to_move + 1;
+        }
+        else  // not first / not last
+        {
+            source = cbuf; 
+            nbytes = 4096;
+        }
+
+        // move data
+        memcpy( dest , source , nbytes );
+        done = done + nbytes;
+    }
 
 #if GIET_DEBUG_FAT
 if ( _get_proctime() > GIET_DEBUG_FAT )
-_fat_print();
-_printf("\n[DEBUG FAT] P[%d,%d,%d] exit _fat_init()\n", x,y,p );
-#endif
-
-    return 0;
-}  // end _fat_init()
-
-///////////////////////////////////////////////////////////////////////////////
-// This function checks that the kernel FAT structure has been initialised.
-// It searches a file identified by the "pathname" argument.
-// It starts from root (cluster 2) to scan successively each subdirectory.
-// When the file is not found, but the path is found, and "creat" is set,
-// a new file is created and introduced in the directory.
-// Finally, it sets a new open file in the file descriptors array.
-// The same file can be open several times by differents tasks.
-///////////////////////////////////////////////////////////////////////////////
-// Returns file descriptor index if success, returns -1 if error.
-///////////////////////////////////////////////////////////////////////////////
-int _fat_open( unsigned int use_irq,       // use descheduling mode if possible
-               char*        pathname,
-               unsigned int creat )
-{
-    char                 name[256];        // buffer for one name in pathname
-    unsigned int         nb_read;              // number of characters written in name[] 
-    unsigned int         cluster;          // current cluster index when scanning FAT
-    unsigned int         dir_cluster;      // previous cluster index when scanning FAT
-    unsigned int         fd_id;            // index when scanning file descriptors array
-    unsigned int         file_size = 0;    // number of bytes
-    unsigned int         last_name = 0;    // directory containing file name is reached
-    unsigned int         lba       = 0;    // lba of dir_entry for this file
-    
+_printf("\n[DEBUG FAT] _fat_read() : P[%d,%d,%d] loaded file <%s> from Cache-File\n",
+        x , y , p , inode->name );
+#endif
+
+    // update seek
+    _fat.fd[fd_id].seek += done;
+
+    // release lock
+    _spin_lock_release( &_fat.fat_lock );
+
+    return done;
+} // end _fat_read()
+
+
+
+
+/////////////////////////////////////////////////////////////////////////////////
+// The following function implements the "giet_fat_write()" system call.
+// It transfers "count" bytes to the fat_cache associated to the file
+// identified by "fd_id", from the user "buffer", using the current file offset.
+// It has the same semantic as the UNIX "write()" function.
+// It increases the file size and allocate new clusters if (count + offset) 
+// is larger than the current file size. Then it loads and updates all 
+// involved clusters in the cache.
+/////////////////////////////////////////////////////////////////////////////////
+// Returns number of bytes actually written if success.
+// Returns a negative value if error:
+//   -1 :  "FAT not initialised"
+//   -2 :  "Illegal file descriptor"
+//   -3 :  "File not open"
+//   -4 :  "File not writable"
+//   -5 :  "No free clusters"
+//   -6 :  "Cannot update parent directory entry"
+//   -7 :  "Cannot access File-Cache"
+/////////////////////////////////////////////////////////////////////////////////
+int _fat_write( unsigned int fd_id,    // file descriptor index
+                void*        buffer,   // source buffer
+                unsigned int count )   // number of bytes to write
+{
+    // checking FAT initialised
+    if( _fat.initialised != FAT_INITIALISED )
+    {
+        _printf("\n[FAT ERROR] in _fat_write() : FAT not initialised\n");
+        return -1;
+    }
+
+    // takes lock
+    _spin_lock_acquire( &_fat.fat_lock );
+           
+    // check fd_id overflow
+    if ( fd_id >= GIET_OPEN_FILES_MAX )
+    {
+        _spin_lock_release( &_fat.fat_lock );
+        _printf("\n[FAT ERROR] in _fat_write() : illegal file descriptor\n");
+        return -2;
+    }
+
+    // check file open
+    if ( _fat.fd[fd_id].allocated == 0 )
+    {
+        _spin_lock_release( &_fat.fat_lock );
+        _printf("\n[FAT ERROR] in _fat_write() : file not open\n" );
+        return -3;
+    }
+
+    // check file writable
+    if ( _fat.fd[fd_id].read_only )
+    {
+        _spin_lock_release( &_fat.fat_lock );
+        _printf("\n[FAT ERROR] in _fat_write() : file <%s> is read-only\n",
+                _fat.fd[fd_id].inode->name );
+        return -4;
+    }
+
+    // get file inode pointer and seek 
+    fat_inode_t* inode  = _fat.fd[fd_id].inode;
+    unsigned int seek   = _fat.fd[fd_id].seek;
+
 #if GIET_DEBUG_FAT
 unsigned int procid  = _get_procid();
@@ -1276 +3282 @@
 unsigned int p       = procid & ((1<<P_WIDTH)-1);
 if ( _get_proctime() > GIET_DEBUG_FAT )
-_printf("\n[DEBUG FAT] _fat_open() : P[%d,%d,%d] enters for path %s\n",
-        x, y, p, pathname );
-#endif
-
-    // checking creat argument
-    if ( creat )
-    {
-        _printf("\n[FAT ERROR] in _fat_open() : create not supported yet\n");
-        return -1;
-    }
-
+_printf("\n[DEBUG FAT] _fat_write() : P[%d,%d,%d] enters for file <%s> "
+        " / bytes = %x / seek = %x\n",
+        x , y , p , inode->name , count , seek );
+#endif
+
+    // chek if file size must be incremented
+    // and allocate new clusters from FAT if required
+    unsigned int old_size = inode->size;
+    unsigned int new_size = seek + count;
+    if ( new_size > old_size )
+    {
+        // update size in inode
+        inode->size = new_size;
+ 
+        // compute current and required numbers of clusters
+        unsigned old_clusters = old_size >> 12;
+        if ( old_size & 0xFFF ) old_clusters++;
+
+        unsigned new_clusters = new_size >> 12;
+        if ( new_size & 0xFFF ) new_clusters++;
+
+        // allocate new clusters from FAT if required
+        if ( new_clusters > old_clusters )
+        {
+
+#if GIET_DEBUG_FAT
+if ( _get_proctime() > GIET_DEBUG_FAT )
+_printf("\n[DEBUG FAT] _fat_write() : P[%d,%d,%d] allocates new clusters for file <%s>"
+        " / current = %d / required = %d\n",
+        x , y , p , inode->name , old_clusters , new_clusters );
+#endif
+            // allocate missing clusters
+            if ( _clusters_allocate( inode,
+                                     old_clusters,
+                                     new_clusters - old_clusters ) )
+            {
+                _spin_lock_release( &_fat.fat_lock );
+                _printf("\n[FAT ERROR] in _fat_write() : no free clusters"
+                        " for file <%s>\n", _fat.fd[fd_id].inode->name );
+                return -5;
+            }
+        }
+         
+        // update parent directory entry (size an cluster index)
+        if ( _update_dir_entry( inode ) )
+        {
+            _spin_lock_release( &_fat.fat_lock );
+            _printf("\n[FAT ERROR] in _fat_write() : cannot update parent directory entry"
+                    " for file <%s>\n", _fat.fd[fd_id].inode->name );
+            return -6;
+        }
+            
+
+#if GIET_DEBUG_FAT
+if ( _get_proctime() > GIET_DEBUG_FAT )
+_printf("\n[DEBUG FAT] _fat_write() : P[%d,%d,%d] updates size for file <%s> / size = %x\n",
+        x , y , p , inode->name , (new_size - old_size) );
+#endif
+
+    }
+
+    // compute first_cluster_id and first_byte_to_move 
+    unsigned int first_cluster_id   = seek >> 12;
+    unsigned int first_byte_to_move = seek & 0xFFF;   
+
+    // compute last_cluster and last_byte_to_move 
+    unsigned int last_cluster_id   = (seek + count - 1) >> 12;   
+    unsigned int last_byte_to_move = (seek + count - 1) & 0xFFF;
+
+#if GIET_DEBUG_FAT
+if ( _get_proctime() > GIET_DEBUG_FAT )
+_printf("\n[DEBUG FAT] _fat_write() : P[%d,%d,%d] starts loop on clusters for file <%s>\n"
+        "  first_cluster_id = %d / first_byte_to_move = %x"
+        " / last_cluster_id = %d / last_byte_to_move = %x\n",
+        x , y , p , inode->name ,
+        first_cluster_id , first_byte_to_move , last_cluster_id , last_byte_to_move );
+#endif
+
+    // loop on all clusters covering the requested transfer
+    unsigned int cluster_id;
+    unsigned int done = 0;
+    for ( cluster_id = first_cluster_id ; cluster_id <= last_cluster_id ; cluster_id++ )
+    {
+        // get pointer on one 4K buffer in File-Cache 
+        unsigned char*     cbuf;
+        fat_cache_desc_t*  pdesc;
+        if ( _get_buffer_from_cache( inode,   
+                                     cluster_id,  
+                                     &pdesc ) )   
+        {
+            _spin_lock_release( &_fat.fat_lock );
+            _printf("\n[FAT ERROR] in _fat_write() : cannot load file <%s>\n",
+                    inode->name );
+            return -7;
+        }
+        
+        cbuf         = pdesc->buffer;
+        pdesc->dirty = 1;
+   
+#if GIET_DEBUG_FAT
+if ( _get_proctime() > GIET_DEBUG_FAT )
+_printf("\n[DEBUG FAT] _fat_write() : P[%d,%d,%d] move cluster_id %d to Cache-file <%s>\n",
+        x , y , p , cluster_id, inode->name );
+#endif
+
+        // compute memcpy arguments
+        unsigned char* source = (unsigned char*)buffer + done;
+        unsigned char* dest;
+        unsigned int   nbytes;
+        if ( (cluster_id == first_cluster_id) && (cluster_id == last_cluster_id) )
+        {
+            dest   = cbuf + first_byte_to_move; 
+            nbytes = last_byte_to_move - first_byte_to_move + 1;
+        }
+        else if ( cluster_id == first_cluster_id )
+        {
+            dest   = cbuf + first_byte_to_move; 
+            nbytes = 4096 - first_byte_to_move;
+        }
+        else if ( cluster_id == last_cluster_id )
+        {
+            dest   = cbuf; 
+            nbytes = last_byte_to_move + 1;
+        }
+        else
+        {
+            dest   = cbuf; 
+            nbytes = 4096;
+        }
+
+        //move date
+        memcpy( dest , source , nbytes ); 
+        done = done + nbytes;
+
+    } // end for clusters
+
+    // update seek
+    _fat.fd[fd_id].seek += done;
+
+#if GIET_DEBUG_FAT
+if ( _get_proctime() > GIET_DEBUG_FAT )
+_printf("\n[DEBUG FAT] _fat_write() : P[%d,%d,%d] store file <%s> into Cache-File\n",
+        x , y , p , inode->name );
+#endif
+
+    // release lock
+    _spin_lock_release( &_fat.fat_lock );
+
+    return done;
+} // end _fat_write()
+
+
+
+/////////////////////////////////////////////////////////////////////////////////
+// The following function implements the "giet_fat_lseek()" system call.
+// It repositions the seek in the file descriptor "fd_id", according to
+// the "seek" and "whence" arguments.
+// It has the same semantic as the UNIX lseek() function.
+// Accepted values for whence are SEEK_SET and SEEK_CUR.
+/////////////////////////////////////////////////////////////////////////////////
+// Returns new seek value (bytes) if success.
+// Returns negative value if error:
+//   -1  : "FAT not initialised"
+//   -2  : "Illegal file descriptor"
+//   -3  : "File not open"
+//   -4  : "Illegal whence argument"
+/////////////////////////////////////////////////////////////////////////////////
+int _fat_lseek( unsigned int fd_id,
+                unsigned int seek,
+                unsigned int whence )
+{
     // checking FAT initialised
     if( _fat.initialised != FAT_INITIALISED )
     {
-        _printf("\n[FAT ERROR] in _fat_open() : FAT not initialised\n");
+        _printf("\n[FAT ERROR] in _fat_lseek() : FAT not initialised\n");
         return -1;
     }
-    // takes the FAT lock for exclusive access
+
+    // check fd_id overflow
+    if ( fd_id >= GIET_OPEN_FILES_MAX )
+    {
+        _printf("\n[FAT ERROR] in _fat_lseek() : illegal file descriptor\n");
+        return -2;
+    }
+
+    // takes lock
     _spin_lock_acquire( &_fat.fat_lock );
 
-#if GIET_DEBUG_FAT
-if ( _get_proctime() > GIET_DEBUG_FAT )
-_printf("\n[DEBUG FAT] _fat_open() : P[%d,%d,%d] takes the FAT lock\n",
-        x, y, p );
-#endif
- 
-    // Scan the directories, starting from the root directory (cluster 2)
-    // - The get_name_from_path() function extracts (successively) 
-    //   each directory name from the pathname, and store it in name[] buffer
-    // - The _scan_directory() function scan one (or several) cluster(s) containing 
-    //   a directory looking for name[], and return the cluster index
-    //   corresponding to the directory/file found.
-    nb_read     = 0;
-    cluster     = 2;
-    last_name   = 0;
-    while ( get_name_from_path( pathname, name, &nb_read) )
-    {
-
-#if GIET_DEBUG_FAT
-if ( _get_proctime() > GIET_DEBUG_FAT )
-_printf("\n[DEBUG FAT] _fat_open() : P[%d,%d,%d] search file/dir %s\n",
-        x, y, p, name );
-#endif
-
-        // test if we reach the last name (file name)
-        if( pathname[nb_read] == 0 )  
-        {
-            last_name   = 1;
-            dir_cluster = cluster;   // this is the lowest directory
-        }
-
-        // scan current directory
-        cluster = _scan_directory( use_irq , cluster , name , &file_size , &lba );
-
-        if( cluster == END_OF_CHAIN_CLUSTER && last_name && creat )
-        {
-            cluster = _fat_create( name, 1, dir_cluster );
-        }
-        else if ( cluster == END_OF_CHAIN_CLUSTER )
-        {
-            _printf("\n[FAT ERROR] in _fat_open() cannot found %s\n", name );
-            _spin_lock_release( &_fat.fat_lock );
-            return -1;
-        }
-    }
-
-#if GIET_DEBUG_FAT
-if ( _get_proctime() > GIET_DEBUG_FAT )
-_printf("\n[DEBUG FAT] P[%d,%d,%d] in _fat_open() : cluster for %s = %x\n",
-       x, y, p, pathname, cluster );
-#endif
-
-    // check the next value for cluster index found
-    unsigned next = _get_next_cluster( use_irq , cluster );
-
-    if ( (next != BAD_CLUSTER) && (next != FREE_CLUSTER) )
-    {
-        // Search an empty slot scanning open file descriptors array
-        fd_id = 0;
-        while ( _fat.fd[fd_id].used != 0 && fd_id < GIET_OPEN_FILES_MAX )
-        {
-            fd_id++;
-        }
-
-        // set file descriptor if found empty slot
-        if ( fd_id < GIET_OPEN_FILES_MAX )
-        {
-            _fat.fd[fd_id].used          = 1;
-            _fat.fd[fd_id].first_cluster = cluster;
-            _fat.fd[fd_id].file_size     = file_size;
-            _fat.fd[fd_id].lba_dir_entry = lba;
-            _strcpy( _fat.fd[fd_id].name, pathname );
-
-#if GIET_DEBUG_FAT
-if ( _get_proctime() > GIET_DEBUG_FAT )
-_printf("\n[DEBUG FAT] _fat_open() : P[%d,%d,%d] exit : fd = %d for file %s\n",
-        x, y, p, fd_id, pathname );
-#endif
-
-            // release FAT lock
-            _spin_lock_release( &_fat.fat_lock );
-
-            return fd_id;
-        }
-        else
-        {
-            _printf("\n[FAT ERROR] in _fat_open() for file %s : fd array full\n", 
-                    pathname );
-            _spin_lock_release( &_fat.fat_lock );
-            return -1;
-        }
-    }
+    // check file open
+    if ( _fat.fd[fd_id].allocated == 0 )
+    {
+        _spin_lock_release( &_fat.fat_lock );
+        _printf("\n[FAT ERROR] in _fat_lseek() : file not open\n");
+        return -3;
+    }
+
+    unsigned int  new_seek;
+
+    // compute new seek
+    if      ( whence == SEEK_CUR ) new_seek = _fat.fd[fd_id].seek + seek;
+    else if ( whence == SEEK_SET ) new_seek = seek;
     else
     {
-        _printf("\n[FAT ERROR] in _fat_open() for file %s : bad cluster\n",
-                pathname );
         _spin_lock_release( &_fat.fat_lock );
-        return -1;
-    }
-} // end _fat_open()
-
-///////////////////////////////////////////////////////////////////////////////
-// For an open file, identified by the file descriptor index, transfer 
-// an integer number of sectors from block device to a memory buffer.
-// If the number of requested sectors exceeds the file size, it is reduced.
-///////////////////////////////////////////////////////////////////////////////
-// Returns number of sectors transfered if success, < 0 if error.
-///////////////////////////////////////////////////////////////////////////////
-int _fat_read( unsigned int use_irq,    // use descheduling mode if possible
-               unsigned int fd_id,      // file descriptor
-               void*        buffer,     // target buffer base address
-               unsigned int count,      // number of sector to read
-               unsigned int offset )    // nuber of sectors to skip in file
-{
-    unsigned int spc = _fat.sectors_per_cluster;
-
-    unsigned int file_size;         // number of bytes in file
-    unsigned int file_sectors;      // number of sectors in file
-    unsigned int total_sectors;     // actual number of sectors to be transfered
-    unsigned int cluster;           // cluster index 
-    unsigned int clusters_to_skip;  // number of clusters to skip because offset
-    unsigned int sectors_to_skip;   // number of sectors to skip in first iteration
-
-    // arguments checking
-    if ( fd_id >= GIET_OPEN_FILES_MAX )
-    { 
-        _printf("\n[FAT ERROR] in _fat_read() : illegal file descriptor index\n");
-        return -1;
-    }
-    if ( _fat.fd[fd_id].used != 1 )
-    {
-        _printf("\n[FAT ERROR] in _fat_read() : file not open\n");
-        return -1;
-    }
-    if ( ((unsigned int)buffer & 0x1FF) != 0 )
-    {
-        _printf("\n[FAT ERROR] in _fat_read() : memory buffer not sector aligned\n");
-        return -1;
-    }
-
-    // compute file size as a number of sectors 
-    file_size    = _fat.fd[fd_id].file_size;
-    if ( file_size & 0x1FF ) file_sectors = (file_size >> 9) + 1;
-    else                     file_sectors = (file_size >> 9); 
-
-    if ( offset >= file_sectors )
-    {
-        _printf("\n[FAT ERROR] offset larger than number of sectors\n");
-        return -1;
-    }
-
-    // compute total number of sectors to read
-    if ( file_sectors < (offset + count) ) total_sectors = file_sectors - offset;
-    else                                   total_sectors = count;
-
-    // compute clusters and sectors to be skipped
-    clusters_to_skip = offset / spc;
-    sectors_to_skip  = offset % spc;
-    
-    // get first cluster index 
-    cluster = _fat.fd[fd_id].first_cluster;
+        _printf("\n[FAT ERROR] in _fat_user_lseek() : illegal whence valuel\n");
+        return -4;
+    }
+
+    // update file descriptor offset 
+    _fat.fd[fd_id].seek = new_seek;
 
 #if GIET_DEBUG_FAT
@@ -1464 +3499 @@
 unsigned int p       = procid & ((1<<P_WIDTH)-1);
 if ( _get_proctime() > GIET_DEBUG_FAT )
-_printf("\n[DEBUG FAT] _fat_read() : P[%d,%d,%d] enters for file %s\n"
-        " - buffer vbase     = %x\n"
-        " - skipped sectors  = %x\n"
-        " - read sectors     = %x\n"
-        " - first cluster    = %x\n"
-        " - skipped clusters = %x\n",
-        x, y, p, _fat.fd[fd_id].name, (unsigned int)buffer,
-        offset, count, cluster, clusters_to_skip );
-#endif
-
-    // compute index of first cluster to be loaded
-    while ( clusters_to_skip )
-    {
-        cluster = _get_next_cluster( use_irq , cluster );
-        clusters_to_skip--;
-    }
-
-    // variables used in the loop on clusters
-    int             todo_sectors;   // number of sectors still to be loaded
-    unsigned int    lba;            // first sector index on device
-    unsigned int    iter_sectors;   // number of sectors to load in iteration
-    unsigned int    dst;            // pointer on target buffer
-
-    // initialize these variables for the first iteration 
-    todo_sectors  = total_sectors;
-    dst           = (unsigned int)buffer;
-    lba           = cluster_to_lba(cluster) + sectors_to_skip;
-    if( total_sectors < (spc - sectors_to_skip) ) iter_sectors = total_sectors;
-    else                                          iter_sectors = spc - sectors_to_skip; 
-
-    // loop on the clusters: one IOC access per cluster
-    while ( todo_sectors > 0 )
-    {
-
-#if GIET_DEBUG_FAT
-if ( _get_proctime() > GIET_DEBUG_FAT )
-_printf("\n[DEBUG FAT] _fat_read() : P[%d,%d,%d] makes an IOC read\n"
-        "  cluster = %x / buffer = %x / lba = %x / sectors = %d\n",
-        x, y, p, cluster, dst, lba, iter_sectors );
-#endif
-
-        if( _fat_ioc_access( use_irq,
-                             1,                 // read
-                             lba, 
-                             dst,               // buffer address
-                             iter_sectors ) )   // number of sectors
-        {
-            _printf("\n[FAT ERROR] in _fat_read() cannot load block %x", lba );
-            return -1;
-        }
-         
-        // update variables for next iteration
-        cluster      = _get_next_cluster( use_irq , cluster );
-        todo_sectors = todo_sectors - iter_sectors;
-        dst          = dst + (iter_sectors << 9);
-        lba          = cluster_to_lba(cluster);
-        if ( todo_sectors > spc ) iter_sectors = spc;
-        else                      iter_sectors = todo_sectors;
-    }
-         
-    // returns number of sectors actually transfered
-    return total_sectors;
-
-}  // end _fat_read() 
-
-///////////////////////////////////////////////////////////////////////////////
-// For an open file, identified by the file descriptor index, transfer 
-// an integer number of sectors from a memory buffer to block device.
-// Allocate new clusters if the offset+count larger than current file size,
-// but the offset should be smaller than the current file size...
-///////////////////////////////////////////////////////////////////////////////
-// Returns number of sectors written if success, < 0 if error.
-///////////////////////////////////////////////////////////////////////////////
-int _fat_write( unsigned int use_irq,    // use descheduling mode if possible
-                unsigned int fd_id,      // file descriptor
-                void*        buffer,     // target buffer base address
-                unsigned int count,      // number of sector to write
-                unsigned int offset )    // nuber of sectors to skip in file
-{
-
-    unsigned int spc = _fat.sectors_per_cluster;
-
-    unsigned int file_size;         // number of bytes in file
-    unsigned int file_sectors;      // number of sectors in file
-    unsigned int cluster;           // cluster index 
-    unsigned int clusters_to_skip;  // number of clusters to skip because offset
-    unsigned int sectors_to_skip;   // number of sectors to skip in first iteration
-    unsigned int allocate;          // need allocate or not
-    unsigned int current_cluster;   // number of cluster allocated to the file
-    unsigned int required_cluster;  // number of cluster needed for the write
-
-    // compute file size as a number of sectors 
-    file_size    = _fat.fd[fd_id].file_size;
-    if ( file_size & 0x1FF ) file_sectors = (file_size >> 9) + 1;
-    else                     file_sectors = (file_size >> 9); 
-
-    // Compute the number of clusters occupied by the file
-    current_cluster = file_sectors / spc;
-
-    // Compute the number of clusters that will occupy the file (after fat_write)
-    required_cluster = (count + offset) / spc;
-
-    // Check if we need to allocate new cluster(s) for the file  
-    allocate = ( required_cluster > current_cluster );
+_printf("\n[DEBUG FAT] _fat_lseek() : P[%d,%d,%d] set seek = %x for file <%s>\n",
+        x , y , p , new_seek , _fat.fd[fd_id].inode->name );
+#endif
+
+    // release lock
+    _spin_lock_release( &_fat.fat_lock );
+
+    return new_seek;
+}  // end _fat_lseek()
+
+
+
+/////////////////////////////////////////////////////////////////////////////////
+// The following function implements the giet_fat_remove() system call. 
+// It deletes the file/directory identified by the "pathname" argument from 
+// the file system, if the remove condition is fulfilled (directory empty,
+// or file not referenced).
+// All clusters allocated in the block device DATA region are released.
+// The FAT region is updated on the block device.
+// The Inode-Tree is updated.
+// The associated File_Cache is released.
+// The Fat_Cache is updated.
+/////////////////////////////////////////////////////////////////////////////////
+// Returns 0 if success.
+// Returns negative value if error
+//   -1  : "FAT not initialised"
+//   -2  : "File/Directory not found"
+//   -3  : "Name too long in path"
+//   -4  : "Has the wrong type"
+//   -5  : "File still open"
+//   -6  : "Cannot scan directory"
+//   -7  : "Directory not empty"
+//   -8  : "Cannot remove file/dir from FS"
+/////////////////////////////////////////////////////////////////////////////////
+int _fat_remove( char*        pathname,
+                 unsigned int should_be_dir )
+{
+    fat_inode_t*  inode;            // searched file inode pointer
 
 #if GIET_DEBUG_FAT
@@ -1575 +3544 @@
 unsigned int p       = procid & ((1<<P_WIDTH)-1);
 if ( _get_proctime() > GIET_DEBUG_FAT )
-_printf("\n[DEBUG FAT] _fat_write() : P[%d,%d,%d] enters for file %s\n"
-        " - buffer vbase    = %x\n"
-        " - skipped sectors = %x\n"
-        " - write sectors   = %x\n"
-        " - file sectors    = %x\n"
-        " - need_allocate   = %d\n",
-        x, y, p, _fat.fd[fd_id].name, (unsigned int)buffer,
-        offset, count, file_sectors, allocate );
-#endif
-
-    // arguments checking
-    if ( fd_id >= GIET_OPEN_FILES_MAX )
-    { 
-        _printf("\n[FAT ERROR] in _fat_write() : illegal file descriptor index\n");
+_printf("\n[DEBUG FAT] _fat_remove() : P[%d,%d,%d] enters for path <%s>\n",
+        x, y, p, pathname );
+#endif
+
+    // checking FAT initialised
+    if( _fat.initialised != FAT_INITIALISED )
+    {
+        _printf("\n[FAT ERROR] in _fat_remove() : FAT not initialised\n");
         return -1;
     }
-    if ( _fat.fd[fd_id].used != 1 )
-    {
-        _printf("\n[FAT ERROR] in _fat_write() : file not open\n");
+
+    // take the lock 
+    _spin_lock_acquire( &_fat.fat_lock );
+
+    // get searched file inode 
+    unsigned int code = _get_inode_from_path( pathname , &inode );
+
+#if GIET_DEBUG_FAT
+if ( _get_proctime() > GIET_DEBUG_FAT )
+_printf("\n[DEBUG FAT] _fat_remove() : P[%d,%d,%d] found inode %x for <%s> / code = %d\n",
+        x , y , p , (unsigned int)inode , pathname , code );
+#endif
+
+    if ( (code == 1) || (code == 2) )
+    {
+        _spin_lock_release( &_fat.fat_lock );
+        _printf("\n[FAT ERROR] in _fat_remove() : file <%s> not found\n", 
+                pathname );
+        return -2;
+    }
+    else if ( code == 3 )
+    {
+        _spin_lock_release( &_fat.fat_lock );
+        _printf("\n[FAT ERROR] in _fat_remove() : name too long in <%s>\n",
+                pathname );
+        return -3;
+    }
+
+    // check inode type
+    if ( (inode->is_dir != 0) && (should_be_dir == 0) ) 
+    {
+        _spin_lock_release( &_fat.fat_lock );
+        _printf("\n[FAT ERROR] in _fat_remove() : <%s> is a directory\n",
+                pathname );
+        return -4;
+    }
+    if ( (inode->is_dir == 0) && (should_be_dir != 0) )
+    {
+        _spin_lock_release( &_fat.fat_lock );
+        _printf("\n[FAT ERROR] in _fat_remove() : <%s> is not a directory\n", 
+                pathname );
+        return -4;
+    }
+
+#if GIET_DEBUG_FAT
+if ( _get_proctime() > GIET_DEBUG_FAT )
+_printf("\n[DEBUG FAT] _fat_remove() : P[%d,%d,%d] checked inode type for <%s>\n",
+        x , y , p , pathname );
+#endif
+    
+    // check references count for a file
+    if ( (inode->is_dir == 0) && (inode->count != 0) )
+    {
+        _spin_lock_release( &_fat.fat_lock );
+        _printf("\n[FAT ERROR] in _fat_remove() : file <%s> still referenced\n",
+                pathname );
+        return -5;
+    }
+
+    //  check empty for a directory
+    if ( inode->is_dir )
+    {
+        unsigned int entries;
+        if ( _get_nb_entries( inode , &entries ) )
+        {
+            _spin_lock_release( &_fat.fat_lock );
+            _printf("\n[FAT ERROR] in _fat_remove() : cannot scan directory <%s>\n", 
+                    pathname );
+            return -6;
+        }
+        else if ( entries > 2 )
+        {
+            _spin_lock_release( &_fat.fat_lock );
+            _printf("\n[FAT ERROR] in _fat_remove() : directory <%s> not empty\n", 
+                    pathname );
+            return -7;
+        }
+    }
+
+#if GIET_DEBUG_FAT
+if ( _get_proctime() > GIET_DEBUG_FAT )
+_printf("\n[DEBUG FAT] _fat_remove() : P[%d,%d,%d] checked remove condition OK for <%s>\n",
+        x , y , p , pathname );
+#endif
+    
+    // remove the file or directory from the file system
+    if ( _remove_node_from_fs( inode ) )
+    {
+        _spin_lock_release( &_fat.fat_lock );
+        _printf("\n[FAT ERROR] in _fat_remove() : cannot remove <%s> from FS\n",
+                pathname );
+        return -8;
+    }
+
+    // release lock and return success
+    _spin_lock_release( &_fat.fat_lock );
+
+#if GIET_DEBUG_FAT
+if ( _get_proctime() > GIET_DEBUG_FAT )
+_printf("\n[DEBUG FAT] _fat_remove() : P[%d,%d,%d] removed  <%s> from FS\n",
+        x, y, p, pathname );
+#endif
+    
+    return 0;
+        
+}  // end _fat_remove()
+
+
+
+
+
+/////////////////////////////////////////////////////////////////////////////////
+// This function implements the giet_fat_rename() system call.
+// It moves an existing file or directory from one node (defined by "old_path"
+// argument) to another node (defined by "new_path" argument) in the FS tree. 
+// The type (file/directory) and content are not modified.
+// If the new_path file/dir exist, it is removed from the file system, but only  
+// if the remove condition is respected (directory empty / file not referenced).
+// The removed entry is only removed after the new entry is actually created.
+/////////////////////////////////////////////////////////////////////////////////
+// Returns 0 if success.
+// Returns a negative value if error:
+//  -1  : "FAT not initialised"
+//  -2  : "old_path not found"
+//  -3  : "new_path not found"
+//  -4  : "cannot scan to_remove directory"
+//  -5  : "to_remove directory not empty"
+//  -6  : "to_remove file still referenced"
+//  -7  : "cannot add new node to new_parent directory"
+//  -8  : "cannot update new_parent directory on device"
+//  -9  : "cannot remove old node from old_parent directory"
+//  -10 : "cannot update old_parent directory on device"
+//  -11 : "cannot remove to_remove node from FS"
+/////////////////////////////////////////////////////////////////////////////////
+int _fat_rename( char*  old_path,
+                 char*  new_path )
+{
+    fat_inode_t*  inode;        // anonymous inode pointer
+    fat_inode_t*  old;          // inode identified by old_path      => to be deleted
+    fat_inode_t*  new;          // inode identified by new_path      => to be created
+    fat_inode_t*  old_parent;   // parent inode  in old_path         => to be modified
+    fat_inode_t*  new_parent;   // parent inode  in new_path         => to be modified
+    fat_inode_t*  to_remove;    // previouly identified by new_path  => to be removed
+    unsigned int  code;
+
+#if GIET_DEBUG_FAT
+unsigned int procid  = _get_procid();
+unsigned int x       = procid >> (Y_WIDTH + P_WIDTH);
+unsigned int y       = (procid >> P_WIDTH) & ((1<<Y_WIDTH)-1);
+unsigned int p       = procid & ((1<<P_WIDTH)-1);
+if ( _get_proctime() > GIET_DEBUG_FAT )
+_printf("\n[DEBUG FAT] _fat_rename() : P[%d,%d,%d] enters to move <%s> to <%s>\n",
+        x , y , p , old_path , new_path );
+#endif
+
+    // checking FAT initialised
+    if( _fat.initialised != FAT_INITIALISED )
+    {
+        _printf("\n[FAT ERROR] in _fat_rename() : FAT not initialised\n");
         return -1;
     }
-    if ( ((unsigned int)buffer & 0x1FF) != 0 )
-    {
-        _printf("\n[FAT ERROR] in _fat_write() : memory buffer not sector aligned\n");
+
+    // take the lock 
+    _spin_lock_acquire( &_fat.fat_lock );
+
+    // get "old" and "old_parent" inode pointers
+    if ( _get_inode_from_path( old_path , &inode ) )
+    {
+        _spin_lock_release( &_fat.fat_lock );
+        _printf("\n[FAT ERROR] in _fat_rename() : <%s> not found\n", old_path );
+        return -2;
+    }
+    else
+    {
+        old        = inode;
+        old_parent = inode->parent;
+    }
+
+    // get "to_removed" and "new_parent" inode pointers
+    code = _get_inode_from_path( new_path , &inode );
+
+    if ( code == 0 )       // new_path inode already exist 
+    {
+        to_remove        = inode;
+        new_parent       = inode->parent;   
+    }
+    else if ( code == 1 )  // to_remove does not exist but parent exist
+    {
+        to_remove        = NULL;
+        new_parent       = inode;
+    }
+    else                   // parent directory in new_path not found
+    {
+        _spin_lock_release( &_fat.fat_lock );
+        _printf("\n[FAT ERROR] in _fat_rename() : <%s> not found\n", new_path );
+        return -3;
+    }
+
+#if GIET_DEBUG_FAT
+if ( _get_proctime() > GIET_DEBUG_FAT )
+{
+if ( to_remove )
+_printf("\n[DEBUG FAT] _fat_rename() : old_parent = %s / old = %s / new_parent = %s "
+        "/ to_remove = %s\n",
+        old_parent->name , old->name , new_parent->name , to_remove->name );
+else
+_printf("\n[DEBUG FAT] _fat_rename() : old_parent = %s / old = %s / new_parent = %s "
+        "/ no remove\n", 
+        old_parent->name , old->name , new_parent->name );
+}
+#endif
+
+    // check remove condition for "to_remove" inode
+    if ( to_remove )
+    {
+        if ( to_remove->is_dir )   // it's a directory
+        {
+            unsigned int entries;
+            if ( _get_nb_entries( to_remove , &entries ) )
+            {
+                _spin_lock_release( &_fat.fat_lock );
+                _printf("\n[FAT ERROR] in _fat_rename() : cannot scan directory <%s>\n", 
+                        to_remove->name );
+                return -4;
+            }
+            else if ( entries > 2 )
+            {
+                _spin_lock_release( &_fat.fat_lock );
+                _printf("\n[FAT ERROR] in _fat_rename() : directory <%s> not empty\n", 
+                        to_remove->name );
+                return -5;
+            }
+        }
+        else                       // it's a file
+        {
+            if ( to_remove->count ) 
+            {
+                _spin_lock_release( &_fat.fat_lock );
+                _printf("\n[FAT ERROR] in _fat_rename() : file <%s> still referenced\n", 
+                        to_remove->name );
+                return -6;
+            }
+        }
+    }
+
+#if GIET_DEBUG_FAT
+if ( _get_proctime() > GIET_DEBUG_FAT )
+_printf("\n[FAT DEBUG] _fat_rename() : P[%d,%d,%d] checked remove condition OK\n",
+        x , y , p );
+#endif
+
+    // get new last name / error checking already done by _get_inode_from_path()
+    char  new_name[32];
+    _get_last_name( new_path , new_name );
+
+    // allocate "new" inode
+    new = _allocate_one_inode( new_name,
+                               old->is_dir,
+                               old->cluster,
+                               old->size,
+                               0,              // count
+                               0,              // dentry
+                               0 );            // no cache_allocate
+ 
+    // give the "old" File-Cache to the "new inode
+    new->levels = old->levels;
+    new->cache  = old->cache;
+
+    // add "new" to "new_parent" directory File-Cache
+    if ( _add_dir_entry( new , new_parent ) )
+    {
+        _spin_lock_release( &_fat.fat_lock );
+        _printf("\n[FAT ERROR] in _fat_rename() : cannot add <%s> into <%s>\n",
+                new->name , new_parent->name );
+        return -7;
+    }
+
+    // add "new" to "new_parent" directory in Inode-Tree
+    _add_inode_in_tree( new , new_parent );
+    
+    // updates "new_parent" directory on device
+    if ( _update_device_from_cache( new_parent->levels,
+                                    new_parent->cache,
+                                    new_parent->name ) )
+    {
+        _spin_lock_release( &_fat.fat_lock );
+        _printf("\n[FAT ERROR] in _fat_rename() : cannot update <%s> on device\n",
+                    new_parent->name );
+        return -8;
+    }
+
+    // remove "old" from "old_parent" File-Cache 
+    if ( _remove_dir_entry( old ) )
+    {
+        _spin_lock_release( &_fat.fat_lock );
+        _printf("\n[FAT ERROR] in _fat_rename() : cannot remove <%s> from <%s>\n",
+                old->name , old_parent->name );
+        return -9;
+    }
+ 
+    // remove "old" inode from Inode-Tree
+    _remove_inode_from_tree( old );
+
+    // updates "old_parent" directory on device
+    if ( _update_device_from_cache( old_parent->levels,
+                                    old_parent->cache,
+                                    old_parent->name ) )
+    {
+        _spin_lock_release( &_fat.fat_lock );
+        _printf("\n[FAT ERROR] in _fat_rename() : cannot update <%s> on device\n",
+                    old_parent->name );
+        return -10;
+    }
+
+    // remove "to_remove" from File System (if required)
+    if ( to_remove )
+    {
+        if ( _remove_node_from_fs( to_remove ) )
+        {
+            _spin_lock_release( &_fat.fat_lock );
+            _printf("\n[FAT ERROR] in _fat_rename() : cannot remove <%s> from FS\n",
+                    to_remove->name );
+            return -11;
+        }
+    }
+
+    // release lock
+    _spin_lock_release( &_fat.fat_lock );
+
+    return 0;
+}  // end _fat_rename()
+
+
+
+
+/////////////////////////////////////////////////////////////////////////////////
+// The following function implements the giet_fat_mkdir() system call.
+// It creates in file system the directory specified by the "pathname" argument.
+// The Inode-Tree is updated.
+// One cluster is allocated to the new directory.
+// The associated File-Cache is created.
+// The FAT region on block device is updated.
+// The DATA region on block device is updated.
+/////////////////////////////////////////////////////////////////////////////////
+// Returns 0 if success.
+// Returns a negative value if error:
+//   -1  : "Fat not initialised"
+//   -2  : "Path to parent not found"
+//   -3  : "One name in path too long"
+//   -4  : "Directory already exist"
+//   -5  : "No free cluster"
+//   -6  : "Cannot update parent directory"
+//   -7  : "Cannot update parent DATA region"
+//   -8  : "Cannot update FAT region"
+//   -9  : "Cannot update FS-INFO"
+//   -10 : "Cannot update directory DATA region"
+/////////////////////////////////////////////////////////////////////////////////
+int _fat_mkdir( char* pathname )
+{
+    fat_inode_t*         inode;            // anonymous inode pointer
+    fat_inode_t*         child;            // searched directory inode pointer
+    fat_inode_t*         parent;           // parent directory inode pointer
+
+#if GIET_DEBUG_FAT
+unsigned int procid  = _get_procid();
+unsigned int x       = procid >> (Y_WIDTH + P_WIDTH);
+unsigned int y       = (procid >> P_WIDTH) & ((1<<Y_WIDTH)-1);
+unsigned int p       = procid & ((1<<P_WIDTH)-1);
+if ( _get_proctime() > GIET_DEBUG_FAT )
+_printf("\n[DEBUG FAT] _fat_mkdir() : P[%d,%d,%d] enters for path <%s>\n",
+        x, y, p, pathname );
+#endif
+
+    // checking FAT initialised
+    if( _fat.initialised != FAT_INITIALISED )
+    {
+        _printf("\n[FAT ERROR] in _fat_mkdir() : FAT not initialised\n");
         return -1;
     }
 
-    if ( allocate  )
-    {
-        if ( _fat_allocate( use_irq , fd_id, (required_cluster-current_cluster) ) )
-        {
-            _printf("\n[FAT ERROR] in _fat_write() : fat_allocate failed\n");
-            return -1;
-        }
-    }
-
-    // compute clusters and sectors to be skipped
-    clusters_to_skip = offset / spc;
-    sectors_to_skip  = offset % spc;
+    // takes the lock
+    _spin_lock_acquire( &_fat.fat_lock );
     
-    // get first cluster index 
-    cluster = _fat.fd[fd_id].first_cluster;
+    // get inode
+    unsigned int code = _get_inode_from_path( pathname , &inode );
+
+    if ( code == 2 )  
+    {
+        _spin_lock_release( &_fat.fat_lock );
+        _printf("\n[FAT ERROR] in _fat_mkdir() : path to parent not found"
+                " for directory <%s>\n", pathname );
+        return -2;
+    }
+    else if ( code == 3 )  
+    {
+        _spin_lock_release( &_fat.fat_lock );
+        _printf("\n[FAT ERROR] in _fat_mkdir() : one name in path too long"
+                " for directory  <%s>\n", pathname );
+        return -3;
+    }
+    else if ( code == 0 )
+    {
+        _spin_lock_release( &_fat.fat_lock );
+        _printf("\n[FAT ERROR] in _fat_mkdir() : directory <%s> already exist\n",
+                pathname );
+        return -4;
+    }
+    else if ( code == 1 )   // directory not found => create 
+    {
+        parent = inode;
 
 #if GIET_DEBUG_FAT
 if ( _get_proctime() > GIET_DEBUG_FAT )
-_printf("\n[DEBUG FAT] _fat_write() : P[%d,%d,%d] get cluster %x\n",
-        x, y, p, cluster );
-#endif
-
-    // compute index of first cluster to be loaded
-    while ( clusters_to_skip )
-    {
-        cluster = _get_next_cluster( use_irq , cluster );
-        clusters_to_skip--;
-    }
-
-    // variables used in the loop on clusters
-    int             todo_sectors;   // number of sectors still to be loaded
-    unsigned int    lba;            // first sector index on device
-    unsigned int    iter_sectors;   // number of sectors to load in iteration
-    unsigned int    src;            // pointer on target buffer
-
-    // initialize these variables for the first iteration 
-    todo_sectors  = count;
-    src           = (unsigned int)buffer;
-    lba           = cluster_to_lba(cluster) + sectors_to_skip;
-    if( count < (spc - sectors_to_skip) ) iter_sectors = count;
-    else                                  iter_sectors = spc - sectors_to_skip; 
-
-    // loop on the clusters
-    while ( todo_sectors > 0 )
-    {
+_printf("\n[DEBUG FAT] _fat_mkdir() : P[%d,%d,%d] create new directory <%s>\n",
+        x , y , p , pathname );
+#endif
+
+        // get directory name / error check already done by _get_inode_from_path()
+        char name[32];       
+        _get_last_name( pathname , name );
+
+        // allocate one cluster from FAT for the new directory
+        unsigned int cluster;
+        if ( _allocate_one_cluster( &cluster ) )
+        {
+            _spin_lock_release( &_fat.fat_lock );
+            _printf("\n[FAT ERROR] in _fat_mkdir() : no free cluster"
+                    " for directory <%s>\n" , pathname );
+            return -5;
+        }
+
+        // allocate a new inode and an empty Cache-File 
+        child = _allocate_one_inode( name,
+                                     1,           // it's a directory
+                                     cluster,  
+                                     0,           // size not defined
+                                     0,           // count
+                                     0,           // dentry set by _add_dir_entry()
+                                     1 );         // cache_allocate
+
+        // introduce inode in Inode-Tree
+        _add_inode_in_tree( child , parent );
+ 
+        // allocate and initialise one 4 Kbytes buffer and associated descriptor
+        _allocate_one_buffer( child,
+                              0,            // cluster_id,
+                              cluster );
+
+        _add_special_directories( child, 
+                                  parent );
+
+        // add an entry in the parent directory Cache_file
+        if ( _add_dir_entry( child , parent ) )
+        { 
+            _spin_lock_release( &_fat.fat_lock );
+            _printf("\n[FAT ERROR] in _fat_mkdir() : cannot update parent directory"
+                    " for directory <%s>\n" , pathname );
+            return -6;
+        } 
+
+        // update DATA region on block device for parent directory
+        if ( _update_device_from_cache( parent->levels,
+                                        parent->cache,
+                                        parent->name ) )
+        {
+            _spin_lock_release( &_fat.fat_lock );
+            _printf("\n[FAT ERROR] in _fat_mkdir() : cannot update DATA region "
+                    " for parent of directory <%s>\n", pathname );
+            return -7;
+        }
+
+        // update FAT region on block device
+        if ( _update_device_from_cache( _fat.fat_cache_levels,
+                                        _fat.fat_cache_root,
+                                        "FAT" ) )
+        {
+            _spin_lock_release( &_fat.fat_lock );
+            _printf("\n[FAT ERROR] in _fat_mkdir() : cannot update FAT region"
+                    " for directory <%s>\n", pathname );
+            return -8;
+        }
+
+        // update FS_INFO sector
+        if ( _update_fs_info() )
+        {
+            _spin_lock_release( &_fat.fat_lock );
+            _printf("\n[FAT ERROR] in _fat_mkdir() : cannot update FS-INFO"
+                    " for directory <%s>\n", pathname );
+            return -9;
+        }
+
+        // update DATA region on block device for the new directory
+        if ( _update_device_from_cache( child->levels,   
+                                        child->cache,
+                                        child->name ) )
+        {
+            _spin_lock_release( &_fat.fat_lock );
+            _printf("\n[FAT ERROR] in _fat_mkdir() : cannot update DATA region"
+                    " for directory <%s>\n", pathname );
+            return -10;
+        }
+    }  // end create directory
+
+    return 0;
+}  // end _fat_mkdir()
+
+
+
+
+
+/////////////////////////////////////////////////////////////////////////////////
+// The following function implements the giet_fat_list() system call.
+// It displays the content of a directory identified by the "pathname" argument.
+// It returns an error code if the pathname is not a directory.
+/////////////////////////////////////////////////////////////////////////////////
+// Returns 0 if success.
+// Returns a negative value if error:
+//   -1  : "FAT not initialised
+//   -2  : "Directory not found"
+//   -3  : "Name in path too long
+//   -4  : "Not a directory"
+//   -5  : "Cannot access directory"
+//   -6  : "Name too long truncated"
+/////////////////////////////////////////////////////////////////////////////////
+int _fat_list( char*  pathname )
+{
+    fat_inode_t*  inode;
+
+    // checking FAT initialised
+    if( _fat.initialised != FAT_INITIALISED )
+    {
+        _printf("\n[FAT ERROR] in _fat_list() : FAT not initialised\n");
+        return -1;
+    }
 
 #if GIET_DEBUG_FAT
-if ( _get_proctime() > GIET_DEBUG_FAT )
-_printf("\n[DEBUG FAT] _fat_write() : P[%d,%d,%d] makes an IOC write"
-        "  cluster = %x / buffer = %x / lba = %x / sectors = %d\n",
-        x, y, p, cluster, src, lba, iter_sectors );
-#endif
-
-        if( _fat_ioc_access( use_irq,
-                             0,                 // write
+unsigned int procid  = _get_procid();
+unsigned int x       = procid >> (Y_WIDTH + P_WIDTH);
+unsigned int y       = (procid >> P_WIDTH) & ((1<<Y_WIDTH)-1);
+unsigned int p       = procid & ((1<<P_WIDTH)-1);
+if ( _get_proctime() > GIET_DEBUG_FAT )
+_printf("\n[DEBUG FAT] _fat_list() : P[%d,%d,%d] enters for path <%s>\n",
+        x, y, p, pathname );
+#endif
+
+    // get inode 
+    unsigned int code = _get_inode_from_path( pathname , &inode );
+
+    if ( (code == 1) || (code == 2) )  
+    {
+        _printf("\n[FAT ERROR] in _fat_list() : directory <%s> not found\n", pathname );
+        return -2;
+    }
+    if ( code == 3 )
+    {
+        _printf("\n[FAT ERROR] in _fat_list() : name too long in path <%s>\n", pathname );
+        return -3;
+    }
+
+    // check found inode is a directory
+    if ( inode->is_dir == 0 )
+    {
+        _printf("\n[FAT ERROR] in _fat_list() : <%s> is not a directory\n", pathname );
+        return -4;
+    }
+
+#if GIET_DEBUG_FAT
+if ( _get_proctime() > GIET_DEBUG_FAT )
+_printf("\n[DEBUG FAT] _fat_list() : P[%d,%d,%d] found inode for path <%s>\n",
+        x, y, p, pathname );
+#endif
+
+    // scan directory up to end of directory / two embedded loops :
+    // - loop on the clusters allocated to the directory
+    // - loop on the directory entries in each 4 Kbytes buffer
+    unsigned char*     buffer;  
+    fat_cache_desc_t*  pdesc;
+    unsigned int       cluster_id = 0;     // cluster index in directory
+    unsigned int       offset     = 0;     // position in scanned buffer
+    unsigned int       lfn        = 0;     // number of lfn entries
+    unsigned int       nb_entries = 0;     // number of directory entries
+    unsigned int       done       = 0;     // end of directory found
+    unsigned int       attr;               // ATTR field value
+    unsigned int       ord;                // ORD field value
+    char               lfn1[16];           // temporary buffer for string in LFN1
+    char               lfn2[16];           // temporary buffer for string in LFN2
+    char               lfn3[16];           // temporary buffer for string in LFN3
+    char               name[36];           // directory entry full name
+    unsigned int       cluster;            // directory entry cluster index
+    unsigned int       size;               // directory entry size
+    unsigned int       is_dir;             // directory entry is a directory
+    unsigned int       is_vid;             // directory entry is volume_id 
+
+    // TODO : define a method to transfer this information to user mode
+    _printf("\n<%s>   cluster = %x / lba = %x\n", pathname ,
+            inode->cluster , _cluster_to_lba( inode->cluster) );
+
+    while ( done == 0 )
+    {
+        // get one 4 Kytes buffer
+        if ( _get_buffer_from_cache( inode,
+                                     cluster_id,
+                                     &pdesc ) ) 
+        {
+            _printf("\n[FAT ERROR] in _fat_list() : cannot access <%s>\n", pathname );
+            return -5;
+        }
+        buffer = pdesc->buffer;
+
+        // scan this 4 Kbytes buffer
+        while ( (offset < 4096)  && (done == 0) )
+        {
+            attr = _read_entry( DIR_ATTR , buffer + offset , 0 );   
+            ord  = _read_entry( LDIR_ORD , buffer + offset , 0 );
+
+            if (ord == NO_MORE_ENTRY)                 // no more entry in directory => break
+            {
+                done = 1;
+            }
+            else if ( ord == FREE_ENTRY )             // free entry => skip
+            {
+                offset = offset + 32;
+            }
+            else if ( attr == ATTR_LONG_NAME_MASK )   // LFN entry => get partial names
+            {
+                unsigned int seq = ord & 0x3;
+                lfn = (seq > lfn) ? seq : lfn;   
+                if      ( seq == 1 ) _get_name_from_long( buffer + offset, lfn1 );
+                else if ( seq == 2 ) _get_name_from_long( buffer + offset, lfn2 );
+                else if ( seq == 3 ) _get_name_from_long( buffer + offset, lfn3 );
+                offset = offset + 32;
+            }
+            else                                 // NORMAL entry
+            {
+                if      ( lfn == 0 )
+                {
+                    _get_name_from_short( buffer + offset , name );
+                }
+                else if ( lfn == 1 )
+                {
+                    _strcpy( name , lfn1 );
+                }   
+                else if ( lfn == 2 ) 
+                {
+                    _strcpy( name      , lfn1 );
+                    _strcpy( name + 13 , lfn2 );
+                }
+                else if ( lfn == 3 ) 
+                {
+                    _strcpy( name      , lfn1 );
+                    _strcpy( name + 13 , lfn2 );
+                    _strcpy( name + 26 , lfn3 );
+                }
+                    
+                is_dir  = ((attr & ATTR_DIRECTORY) == ATTR_DIRECTORY);
+                is_vid  = ((attr & ATTR_VOLUME_ID) == ATTR_VOLUME_ID);
+                size    = (_read_entry( DIR_FILE_SIZE   , buffer + offset , 1 )      ) ;
+                cluster = (_read_entry( DIR_FST_CLUS_HI , buffer + offset , 1 ) << 16) |
+                          (_read_entry( DIR_FST_CLUS_LO , buffer + offset , 1 )      ) ;
+
+                if ( is_vid == 0 )
+                {
+                    // TODO : define a method to transfer this information to user mode
+                    if (is_dir) _printf("  DIR  | size = %X | cluster = %X | %s\n",
+                                        size , cluster, name );
+                    else        _printf("  FILE | size = %X | cluster = %X | %s\n",
+                                        size , cluster, name );
+                    nb_entries++;
+                }
+                
+                offset = offset + 32;
+                lfn    = 0;
+            }
+        }  // end loop on directory entries
+
+        if ( done == 0 )
+        {
+            cluster_id++;
+            offset = 0;
+        }
+    }  // end loop on buffers
+
+    // TODO : define a method to transfer this information to user mode
+    _printf("  total = %d entries\n", nb_entries );
+
+    return 0;
+} // end _fat_list()
+
+
+
+
+
+///////////////////////////////////////////////////////////////////////////////
+// This functiond load a file identified by the "pathname" argument into the
+// memory buffer defined by the "buffer_vbase" and "buffer_size" arguments.
+// It is intended to be called by the boot-loader, as it does not use the
+// dynamically allocated FAT structures (Inode-Tree, Fat_Cache or File-Cache,
+// File-Descriptor-Array).
+// It uses only the 512 bytes buffer defined in the FAT descriptor. 
+///////////////////////////////////////////////////////////////////////////////
+// Returns  0 if success.
+// Returns negative value if error:
+//  -1  : "FAT not initialised"
+//  -2  : "File not found"
+//  -3  : "Buffer too small"
+//  -4  : "Cannot access block device"
+//  -5  : "Cannot access FAT on block device"
+///////////////////////////////////////////////////////////////////////////////
+int _fat_load_no_cache( char*        pathname,
+                        unsigned int buffer_vbase,  
+                        unsigned int buffer_size ) 
+{
+    // checking FAT initialised
+    if( _fat.initialised != FAT_INITIALISED )
+    {
+        _printf("\n[FAT ERROR] in _fat_load_no_cache() : FAT not initialised\n");
+        return -1;
+    }
+
+    unsigned int  file_size;
+    unsigned int  cluster;
+
+#if GIET_DEBUG_FAT
+unsigned int procid  = _get_procid();
+unsigned int x       = procid >> (Y_WIDTH + P_WIDTH);
+unsigned int y       = (procid >> P_WIDTH) & ((1<<Y_WIDTH)-1);
+unsigned int p       = procid & ((1<<P_WIDTH)-1);
+if ( _get_proctime() > GIET_DEBUG_FAT )
+_printf("\n[DEBUG FAT] _fat_load_no_cache() : P[%d,%d,%d] enters for file <%s>\n",
+        x , y , p , pathname );
+#endif
+
+    // get file size, and cluster index in FAT
+    if ( _file_info_no_cache( pathname,
+                              &cluster,
+                              &file_size ) )
+    {
+        _printf("\n[FAT ERROR] in _fat_load_no_cache() : file <%s> not found\n",
+        pathname );
+        return -2;
+    }
+
+    // check buffer size
+    if ( file_size > buffer_size )
+    {
+        _printf("\n[FAT ERROR] in _fat_load_no_cache() : buffer too small : "
+                "file_size = %x / buffer_size = %x", file_size , buffer_size );
+        return -3;
+    }
+
+    // compute total number of clusters to read
+    unsigned int nb_clusters = file_size >> 12;
+    if ( file_size & 0xFFF ) nb_clusters++;
+
+    // initialise buffer address
+    unsigned int dst = buffer_vbase;
+
+    // loop on the clusters containing the file
+    while ( nb_clusters > 0 )
+    {
+        unsigned int lba = _cluster_to_lba( cluster );
+
+        if( _fat_ioc_access( 0,         // no descheduling
+                             1,         // read
                              lba, 
-                             src,               // source buffer address
-                             iter_sectors ) )   // number of sectors
-        {
-            _printf("\n[FAT ERROR] in _fat_write() cannot write block %x\n", lba );
-            return -1;
+                             dst, 
+                             8 ) )      // 8 blocks
+        {
+            _printf("\n[FAT ERROR] in _fat_no _cache_read() : cannot load lba %x", lba );
+            return -4;
         }
          
+
+        // compute next cluster index
+        unsigned int next;
+        if ( _next_cluster_no_cache( cluster , &next ) )
+        {
+            _printf("\n[FAT ERROR] in _fat_no _cache_read() : cannot get next cluster "
+                    " for cluster = %x\n", cluster );
+            return -5;
+        }
+        
         // update variables for next iteration
-        cluster      = _get_next_cluster( use_irq , cluster );
-        todo_sectors = todo_sectors - iter_sectors;
-        src          = src + (iter_sectors << 9);
-        lba          = cluster_to_lba(cluster);
-        if ( todo_sectors > spc ) iter_sectors = spc;
-        else                      iter_sectors = todo_sectors;
-    }
-
-    // Update structure file descriptor, field file_size with
-    // the new file size if the file is bigger than the previous file
-    if ( ( offset + count ) > file_sectors )
-    {
-        _fat.fd[fd_id].file_size = (count + offset) << 9;
-    }
-
-    // Update entry of directory with the new value 
-    // of file size (Field : DIR_FILE_SIZE)
-    if ( _update_entry( use_irq, fd_id , DIR_FILE_SIZE , _fat.fd[fd_id].file_size ) )
-    {
-        _printf("\n[FAT ERROR] in _fat_write() update entry failed\n");
-        return -1;
+        nb_clusters = nb_clusters - 1;
+        dst         = dst + 4096;
+        cluster     = next;
     }
          
-    // returns number of sectors actually transfered
-    return count;
-}  // end _fat_write()
-
-/////////////////////////////////////////////////////////////////////////////////
-// Return stats of a file identified by "fd". 
-// (Only the file_size in sectors for this moment)
-/////////////////////////////////////////////////////////////////////////////////
-// Returns file size (on sectors) on success, -1 on failure.
-/////////////////////////////////////////////////////////////////////////////////
-int _fat_fstat( unsigned int fd_id )
-{
-    unsigned int file_size    = 0;
-    unsigned int file_sectors = 0;
-
-    if( (fd_id < GIET_OPEN_FILES_MAX) )
-    {
-        file_size = _fat.fd[fd_id].file_size;
-
-        if ( file_size & 0x1FF ) file_sectors = (file_size >> 9) + 1;
-        else                     file_sectors = (file_size >> 9); 
-
-        return file_sectors;
-    }
-    else
-    {
-        _printf("\n[FAT ERROR] in _fat_fstat() : illegal file descriptor index\n");
-        return -1;
-    } 
-} // end _fat_fstat()
-
-/////////////////////////////////////////////////////////////////////////////////
-// Close the file identified by the file_descriptor index. 
-/////////////////////////////////////////////////////////////////////////////////
-// Returns 0 on success, -1 on failure.
-/////////////////////////////////////////////////////////////////////////////////
-int _fat_close( unsigned int fd_id )
-{
-    if( (fd_id < GIET_OPEN_FILES_MAX) )
-    {
-        _fat.fd[fd_id].used = 0;
-        return 0;
-    }
-    else
-    {
-        _printf("\n[FAT ERROR] in _fat_close() : illegal file descriptor index\n");
-        return -1;
-    } 
-} // end fat_close()
-
-/////////////////////////////////////////////////////////////////////////////////
-// The following function implement the user_level system call.
-// The flags argument is not used, as file access modes are not implemented yet.
-/////////////////////////////////////////////////////////////////////////////////
-// Return the file descriptor index if success / return -1 if failure
-/////////////////////////////////////////////////////////////////////////////////
-int _fat_user_open( char*  pathname,         // absolute pathname from root
-                    unsigned int flags )     // unused: TODO
-{
-    return _fat_open( 1,        // use descheduling mode if possible
-                      pathname, 
-                      0 );      // no creation if not found
-}
-
-/////////////////////////////////////////////////////////////////////////////////
-// The following function implement the user_level system call.
-// This function should be modified to respect the UNIX specification.
-/////////////////////////////////////////////////////////////////////////////////
-// Return number of sectors actually transfered if success / return -1 if failure
-/////////////////////////////////////////////////////////////////////////////////
-int _fat_user_read( unsigned int fd,        // file descriptor index
-                    void*        buffer,    // destination buffer
-                    unsigned int count,     // number of sectors to read
-                    unsigned int offset )   // number of sectors to skip
-{
-    return _fat_read( 1,        // use descheduling mode if possible
-                      fd,
-                      buffer,  
-                      count,  
-                      offset );
-}
-
-/////////////////////////////////////////////////////////////////////////////////
-// The following function implement the user_level system call.
-// This function should be modified to respect the UNIX specification. 
-/////////////////////////////////////////////////////////////////////////////////
-// Return number of sectors actually transfered if success / return -1 if failure
-/////////////////////////////////////////////////////////////////////////////////
-int _fat_user_write( unsigned int fd,       // file descriptor
-                     void*        buffer,   // source buffer
-                     unsigned int count,    // number of sectors to write
-                     unsigned int offset )  // number of sectors to skip on file
-{
-    return _fat_write( 1,       // use descheduling mode if possible
-                       fd,
-                       buffer,  
-                       count,  
-                       offset );
-}
-
-/////////////////////////////////////////////////////////////////////////////////
-int _fat_user_lseek( unsigned int fd_id,
-                     unsigned int offset,
-                     unsigned int whence )
-{
-    _printf("\n[GIET ERROR] _fat_user_lseek() not implemented\n");
-    _exit();
+#if GIET_DEBUG_FAT
+if ( _get_proctime() > GIET_DEBUG_FAT )
+_printf("\n[DEBUG FAT] _fat_load_no_cache() : P[%d,%d,%d] loaded <%s> at vaddr = %x"
+        " / size = %x\n", x , y , p , pathname , buffer_vbase , file_size );
+#endif
+
     return 0;
-}
+}  // end _fat_load_no_cache() 
+
 
 

soft/giet_vm/giet_fat32/fat32.h

@@ -2 +2 @@
 // File     : fat32.h 
 // Date     : 01/09/2013
-// Author   : Marco Jankovic / Alain Greiner
+// Author   : Alain Greiner / Marco Jankovic
 // Copyright (c) UPMC-LIP6
 ////////////////////////////////////////////////////////////////////////////////
@@ -68 +68 @@
 #define FS_SIGNATURE_POSITION_2           484 , 4
 #define FS_SIGNATURE_POSITION_3           508 , 4  
-#define FS_FREE_CLUSTER                   488 , 4
+#define FS_FREE_CLUSTERS                  488 , 4
 #define FS_FREE_CLUSTER_HINT              492 , 4
 /*******************************************************************************/
@@ -74 +74 @@
 #define DIR_ENTRY_SIZE          32
                    
+#define NAME_MAX_SIZE           31
+
 /******* Directory Entry Structure (32 bytes) **********************************/
-//                          offset | length
-#define DIR_NAME                 0 , 11   // dir_entry name
-#define DIR_ATTR                11 ,  1   // attributes
-#define DIR_NTRES               12 ,  1   // reserved for the OS        
-#define DIR_CRT_TIMES_TENTH     13 ,  1 
-#define DIR_FST_CLUS_HI         20 ,  2   // cluster index 16 MSB bits
-#define DIR_WRT_TIME            22 ,  2   // time of last write
-#define DIR_WRT_DATE            24 ,  2   // date of last write
-#define DIR_FST_CLUS_LO         26 ,  2   // cluster index 16 LSB bit
-#define DIR_FILE_SIZE           28 ,  4   // file size (up to 4 giga bytes)
+//                            offset | length
+#define DIR_NAME                   0 , 11   // dir_entry name
+#define DIR_ATTR                  11 ,  1   // attributes
+#define DIR_NTRES                 12 ,  1   // reserved for the OS        
+#define DIR_CRT_TIMES_TENTH       13 ,  1 
+#define DIR_FST_CLUS_HI           20 ,  2   // cluster index 16 MSB bits
+#define DIR_WRT_TIME              22 ,  2   // time of last write
+#define DIR_WRT_DATE              24 ,  2   // date of last write
+#define DIR_FST_CLUS_LO           26 ,  2   // cluster index 16 LSB bit
+#define DIR_FILE_SIZE             28 ,  4   // file size (up to 4 giga bytes)
 /*******************************************************************************/
 
 /******* LFN Directory Entry Structure  (32 bytes) *****************************/
-//                          offset | length
-#define LDIR_ORD                 0 ,  1   // Sequence number (from 0x01 to 0x0f)    
-#define LDIR_NAME_1              1 , 10   // name broken into 3 parts 
-#define LDIR_ATTR               11 ,  1   // attributes (must be 0x0F) 
-#define LDIR_TYPE               12 ,  1   // directory type (must be 0x00)
-#define LDIR_CHKSUM             13 ,  1   // checksum of name in short dir  
-#define LDIR_NAME_2             14 , 12 
-#define LDIR_RSVD               26 ,  2   // artifact of previous fat (must be 0)
-#define LDIR_NAME_3             28 ,  4   
+//                            offset | length
+#define LDIR_ORD                   0 ,  1   // Sequence number (from 0x01 to 0x0f)    
+#define LDIR_NAME_1                1 , 10   // name broken into 3 parts 
+#define LDIR_ATTR                 11 ,  1   // attributes (must be 0x0F) 
+#define LDIR_TYPE                 12 ,  1   // directory type (must be 0x00)
+#define LDIR_CHKSUM               13 ,  1   // checksum of name in short dir  
+#define LDIR_NAME_2               14 , 12 
+#define LDIR_RSVD                 26 ,  2   // artifact of previous fat (must be 0)
+#define LDIR_NAME_3               28 ,  4   
 /*******************************************************************************/
 
 /***********************  DIR_ATTR values  (attributes) ************************/
-#define ATTR_READ_ONLY          0x01
-#define ATTR_HIDDEN             0x02
-#define ATTR_SYSTEM             0x04
-#define ATTR_VOLUME_ID          0x08
-#define ATTR_DIRECTORY          0x10
-#define ATTR_ARCHIVE            0x20
-#define ATTR_LONG_NAME_MASK     0x0f      // READ_ONLY|HIDDEN|SYSTEM|VOLUME_ID
+#define ATTR_READ_ONLY            0x01
+#define ATTR_HIDDEN               0x02
+#define ATTR_SYSTEM               0x04
+#define ATTR_VOLUME_ID            0x08
+#define ATTR_DIRECTORY            0x10
+#define ATTR_ARCHIVE              0x20
+#define ATTR_LONG_NAME_MASK       0x0f      // READ_ONLY|HIDDEN|SYSTEM|VOLUME_ID
 /*******************************************************************************/
 
 /********************* DIR_ORD special values **********************************/
-#define FREE_ENTRY              0xE5     // this entry is free in the directory
-#define NO_MORE_ENTRY           0x00     // no more entry in the directory
+#define FREE_ENTRY                0xE5     // this entry is free in the directory
+#define NO_MORE_ENTRY             0x00     // no more entry in the directory
 /*******************************************************************************/
 
 /******************** CLuster Index Special Values *****************************/
-#define FREE_CLUSTER            0x00000000
-#define RESERVED_CLUSTER        0x00000001
-#define BAD_CLUSTER             0x0FFFFFF7
-#define END_OF_CHAIN_CLUSTER    0x0ffffff8
-/*******************************************************************************/
+#define FREE_CLUSTER              0x00000000
+#define RESERVED_CLUSTER          0x00000001
+#define BAD_CLUSTER               0x0FFFFFF7
+#define END_OF_CHAIN_CLUSTER_MIN  0x0ffffff8
+#define END_OF_CHAIN_CLUSTER_MAX  0x0fffffff
+/*******************************************************************************/
+
+
+#define SEEK_SET                0
+#define SEEK_CUR                1
 
 #define FAT_INITIALISED         0xBABEF00D
 
-/************ This struct defines a file descriptor ****************************/
-typedef struct file_descriptor_s
-{
-   unsigned int  used;                      // descriptor contains an open file
-   unsigned int  first_cluster;             // first cluster index on disk
-   unsigned int  file_size;                 // number of bytes    
-   unsigned int  lba_dir_entry;             // lba of dir_entry for an open file 
-   char          name[244];                 // pathname
-}  file_desc_t;
-/*******************************************************************************/
-
-/************ This struct describes a FAT32 disk *******************************/
-typedef struct fat32_fs_s
-{
-    char            fat_cache[512];          // FAT cache: 1 sector  
-    spin_lock_t     fat_lock;                // lock protecting exclusive access
-    file_desc_t     fd[GIET_OPEN_FILES_MAX]; // file descriptors array
-    unsigned int    initialised;             // 0xBABEF00D when FAT initialised
-    unsigned int    sector_size;             // number of bytes (power of 2)
-    unsigned int    sectors_per_cluster;     // power of 2 (must be greater than 4)
-    unsigned int    cluster_size;            // sector_size * sector_per_cluster 
-    unsigned int    fat_sectors;             // number of sectors for 1 FAT copy
-    unsigned int    fat_lba;                 // lba of first FAT sector
-    unsigned int    data_lba;                // lba of first data sector  
-    unsigned int    cache_lba;               // lba of sector loaded in fat_cache
-    unsigned int    last_cluster_allocated;  // Last known cluster allocated
-    unsigned int    number_free_cluster;     // number of free clusters
-    unsigned int    fs_info_lba;             // lba of fs_info
-} fat32_fs_t;
-/*******************************************************************************/
+#define O_RDONLY                0x01
+#define O_CREATE                0x20
+
+/********************************************************************************
+  This struct defines a non terminal node in a 64-tree implementing a File-Cache 
+  associated to an open file, or the Fat-Cache, associated to the FAT itself.
+  Each node has 64 children, and we use the void* type, because the children
+  can be non-terminal (fat_cache_node_t) or terminal (fat_cache_cluster_t).
+********************************************************************************/
+
+typedef struct fat_cache_node_s
+{
+    void*              children[64];           // pointers on the 64 children
+}   fat_cache_node_t;
+
+
+/********************************************************************************
+  This struct defines a cluster descriptor, that is a leaf cell in a 64-tree.
+  Each cluster descriptor contains a pointer on a 4K bytes buffer, and the
+  lba on block device.
+********************************************************************************/
+
+typedef struct fat_cache_desc_s
+{
+    unsigned int       lba;                      // cluster lba on block device
+    unsigned int       dirty;                    // modified if non zero
+    unsigned char*     buffer;                   // pointer on the 4 Kbytes buffer
+}   fat_cache_desc_t;
+
+
+/********************************************************************************
+  This struct defines a file/directory inode / size = 64 bytes
+********************************************************************************/
+
+typedef struct fat_inode_s
+{
+    struct fat_inode_s*  parent;                 // parent directory inode
+    struct fat_inode_s*  next;                   // next inode in same directory
+    struct fat_inode_s*  child;                  // first children inode (dir only)
+    fat_cache_node_t*    cache;                  // pointer on the file_cache root
+    unsigned int         cluster;                // first cluster index in FAT
+    unsigned int         size;                   // number of bytes (file only)
+    unsigned int         count;                  // number open if file / 0 if dir
+    unsigned short       dentry;                 // directory entry index in parent
+    unsigned char        levels;                 // number of levels in file_cache
+    unsigned char        is_dir;                 // directory if non zero
+    char                 name[32];               // file  directory name
+}   fat_inode_t;
+
+/********************************************************************************
+  This struct defines a file descriptor (handler) / size = 16 bytes
+********************************************************************************/
+
+typedef struct fat_file_desc_s
+{
+    unsigned int         seek;                   // current offset value (bytes)
+    fat_inode_t*         inode;                  // pointer on inode
+    char                 allocated;              // file descriptor allocated
+    char                 read_only;              // write protected
+    char                 reserved[6];            // reserved
+}   fat_file_desc_t;
+
+/********************************************************************************
+  This struct defines a FAT32 File system descriptor
+ *******************************************************************************/
+
+typedef struct fat_desc_s
+{
+    unsigned char       block_buffer[512];       // one block buffer (for FS_INFO)
+    fat_file_desc_t     fd[GIET_OPEN_FILES_MAX]; // file descriptors array
+    spin_lock_t         fat_lock;                // global lock protecting FAT
+    fat_inode_t*        inode_tree_root;         // Inode-Tree root pointer
+    fat_cache_node_t*   fat_cache_root;          // Fat_Cache root pointer
+    unsigned int        fat_cache_levels;        // number of levels in Fat-Cache
+    unsigned int        block_buffer_lba;        // lba of block in block_buffer
+    unsigned int        initialised;             // 0xBABEF00D when FAT initialised
+    unsigned int        sector_size;             // must be 512
+    unsigned int        cluster_size;            // must be 4096 
+    unsigned int        fat_lba;                 // lba of first FAT sector
+    unsigned int        fat_sectors;             // number of sectors in FAT region
+    unsigned int        data_lba;                // lba of first DATA sector  
+    unsigned int        data_sectors;            // number of sectors inf DATA region 
+    unsigned int        fs_info_lba;             // lba of fs_info
+    unsigned int        first_free_cluster;      // free cluster with smallest index
+    unsigned int        free_clusters_number;    // total number of free clusters
+}   fat_desc_t;
+
 
 /*********************** Extern Functions  *************************************/
 
-extern int _fat_init( unsigned int use_irq );       // use IRQ if possible
-
-extern int _fat_open(  unsigned int use_irq,        // use IRQ if possible
-                       char*  pathname,             // file pathname from root
-                       unsigned int create );       // create new file if non zero
-
-extern int _fat_read(  unsigned int use_irq,        // use IRQ if possible
-                       unsigned int fd_id,          // file descriptor index 
-                       void*        buffer,         // destination buffer
-                       unsigned int count,          // number of sectors to read
-                       unsigned int offset );       // offset sector in file
-
-extern int _fat_write( unsigned int use_irq,        // use IRQ if possible
-                       unsigned int fd_id,          // file descriptor index
-                       void*        buffer,                 // source buffer
-                       unsigned int count,          // number of sectors to write
-                       unsigned int offset );       // offset sector in file
-
-extern int _fat_fstat( unsigned int fd_id );        // file descriptor index
-
-extern int _fat_close( unsigned int fd_id );        // file descriptor index
-
-
-extern int _fat_user_open( char*        pathname,   // file pathname from root
-                           unsigned int flags );    // unused
-
-extern int _fat_user_read(  unsigned int fd_id,     // file descriptor index
-                            void*        buffer,    // destination buffer
-                            unsigned int count,     // number of sectors to read
-                            unsigned int offset );  // sectors to skip in file
-
-extern int _fat_user_write( unsigned int fd_id,     // file descriptor index
-                            void*        buffer,    // source buffer
-                            unsigned int count,     // number of sectors to write
-                            unsigned int offset );  //  sectors to skip in file
-
-extern int _fat_user_lseek( unsigned int fd_id,
-                            unsigned int offset,
-                            unsigned int whence );  
+extern int _fat_init();         
+
+extern int _fat_open( char*        pathname,               // path from root
+                      unsigned int flags );                // O_CREATE/O_RDONLY
+
+extern int _fat_close( unsigned int fd_id );               // file descriptor
+
+extern int _fat_file_info( unsigned int  fd_id,            // file descriptor 
+                           unsigned int* size,             // file size
+                           unsigned int* offset );         // current offset 
+
+extern int _fat_read( unsigned int fd_id,                  // file descriptor  
+                      void*        buffer,                 // destination buffer
+                      unsigned int count );                // number of bytes
+
+extern int _fat_write( unsigned int fd_id,                 // file descriptor 
+                       void*        buffer,                        // source buffer
+                       unsigned int count );               // number of bytes
+
+extern int _fat_lseek( unsigned int fd_id,                 // file descriptor
+                       unsigned int offset,                // new offset value
+                       unsigned int whence );              // command type
+
+extern int _fat_remove( char*        pathname,             // path from root
+                        unsigned int should_be_dir );      // for checking
+
+extern int _fat_rename( char*  old_path,                   // path from root
+                        char*  new_path );                 // path from root
+
+extern int _fat_mkdir( char* pathname );                   // path from root
+
+extern int _fat_list( char* pathname );                    // path from root
+
+extern int _fat_load_no_cache( char*        pathname,      // path from root
+                               unsigned int buffer_vbase,  // buffer base 
+                               unsigned int buffer_size ); // buffer size
 
 /*******************************************************************************/