Changes between Version 6 and Version 7 of file_system

Timestamp:

Jun 7, 2015, 12:31:45 PM (11 years ago)

Author:

alain

Comment:

--

file_system

@@ -3 +3 @@
 [[PageOutline]]
 
-This section describes  GIET_VM [wiki:library_stdio system calls] and [wiki:user_libraries user libraries]. The multi-threaded applications have been designed to analyse the TSAR manycore architecture scalability. 
+This section describes  the GIET_VM File System, that respect the FAT32 standard.
 
 == 1) General Principles ==
@@ -27 +27 @@
 
  * The global Fat_Descriptor contains general information such as the FAT region lba and size, the DATA region lba and size, and pointers on the Fat-Cache or Inode-Tree. 
+
+To support various block device peripheral, this FAT32 implementation defines a generic function to access the physical block device, using the driver specified in the ''hard_config.h'' file. Five drivers are presently supported ( IOC_BDV / IOC_HBA / IOC_SDC / IOC_SPI / IOC_RDK ).
 
 WARNING 1: A node name (file or directory) cannot be larger than 38 characters.
@@ -56 +58 @@
 for each modified block.
 
-== 4) Block Device Drivers ==
-
-To support various block device peripheral, this FAT32 implementation defines a generic _fat_ioc_access() function to access the physical block device. This function transfer one or several blocks between the block device and the file_cache by calling the relevant driver.
-
-=== int '''_fat_ioc_access'''( unsigned int use_irq ,  unsigned int to_mem ,  unsigned int lba , unsigned int buf_vaddr , unsigned int count ) ===
- * '''use_irq''' : boolean (use descheduling mode if supported by the IOC driver)
- * '''to_mem''' : boolean (from block device to memory if non zero) 
- * '''lba''' : logical block address on block device
- * '''buf_vaddr''' : memory buffer virtual address
- * ''' count''' : number of blocks to be transferred
-
-== 5) Access Functions ==
+== 4) Access Functions ==
 
 === int '''_fat_init'''( unsigned int use_irq ) ===
 This function initializes the statically defined FAT structures:
- *  Fat-Descriptor 
- *  File-Descriptors-Array
- *  Fat_Cache root
- *  Inode_Tree root
+ *  Fat-Descriptor.
+ *  File-Descriptors-Array.
+ *  Fat-Cache root.
+ *  Inode-Tree root.
 As is called by the boot-loader, and by the kernel_init, it does not use dynamic memory allocation.
 The polling/descheduling mode is defined by the '''use_irq''' argument.
@@ -99 +90 @@
 It returns 0 if success /  It returns -1 if failure.
 
+=== int '''_fat_file_info( unsigned int fd_id , unsigned int* size , unsigned int* offset ) ===
+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. 
+ * '''fd_id''' : file descriptor index 
+ * '''size''' : pointer on the size (return buffer)
+ * '''offset''' : pointer on the offset (return buffer) 
+It returns 0 if success /  It returns -1 if failure. 
 
+=== int '''_fat_read'''( unsigned int fd_id , void* buffer , unsigned int count ) ===
+The following function implements the "giet_fat_read()" system call, that has the same semantic as the UNIX "read()" function.
+It access the File-Cache  associated to the file identified by the file descriptor, and transfers "count" bytes from the cache to the user buffer, starting from the current file offset.
+In case of miss in the File_Cache, it loads all involved clusters into the cache.
+ * '''fd_id''' : file descriptor index 
+ * '''buffer''' : pointer on the memory buffer
+ * '''count''' : number of bytes 
+It returns the number of bytes actually transfered if success / It returns 0 if (offset + count > file_size) / It returns -1 if failure.
+
+=== int '''_fat_write'''( unsigned int fd_id , void* buffer , unsigned int count ) ===
+The following function implements the "giet_fat_write()" system call, that has the same semantic as the UNIX "write()" function.
+It access the File-Cache associated to the file identified by the file descriptor, and transfers count bytes from the user buffer,
+to the cache, starting from the current file offset. It loads all involved clusters into cache if required. If (offset + count) is larger than the current file size, it increases the file size. It allocates new clusters if required, and updates the Fat-Cache and the FAT region on block device. As it implements a Write-Back policy, the DATA region on block device is not updated, but the modified clusters are marked dirty.
+ * '''fd_id''' : file descriptor index 
+ * '''buffer''' : pointer on the memory buffer
+ * '''count''' : number of bytes 
+It returns the number of bytes actually transfered if success / It returns -1 if failure.
+
+=== int '''_fat_ioc_access'''( unsigned int use_irq ,  unsigned int to_mem ,  unsigned int lba , unsigned int buf_vaddr , unsigned int count ) ===
+This function transfer one or several blocks between the block device and a memory buffer by calling the relevant driver.
+ * '''use_irq''' : boolean (use descheduling mode if supported by the IOC driver)
+ * '''to_mem''' : boolean (from block device to memory if non zero) 
+ * '''lba''' : logical block address on block device
+ * '''buf_vaddr''' : memory buffer virtual address
+ * ''' count''' : number of blocks to be transferred
+It returns 0 if success /  It returns -1 if failure.
+