= GIET-VM  / FAT32 Handler =

This section define the kernel data structure and functions that are used to access a FAT32 file system stored on a mass storage block device (such as BDV, HBA, SDC, or RDK peripherals).

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 * The [source:soft/giet_vm/giet_fat32/fat_sync.c fat_sync.c] and [source:soft/giet_vm/giet_fat32/fat_sync.h fat_sync.h] files define the functions to access the block device with a polling policy on the peripheral status.
 * The [source:soft/giet_vm/giet_fat32/fat_irq.c fat_irq.c] and [source:soft/giet_vm/giet_fat32/fat_irq.h fat_irq.h] files define the functions to access the block device with a a descheduling / completion IRQ policy. 
 * The [source:soft/giet_vm/giet_fat32/fat_common.c fat_common.c] and [source:soft/giet_vm/fat_common.h fat_common.h] files define the functions that are independant on the
blockdevice access mode.

All these functions are prefixed by ''_'' to remind that they can only be executed by a processor in kernel mode.

The [source:soft/giet_vm/giet_kernel/sys_handler.c _syscall_vector] array contains the 64 kernel functions (syscal handlers) defined by the GIET-VM to handle system calls.

== Common FAT32 access functions  ==

== Polling based FAT32 access functions  ==

The following functions are intended to be used by the GIET_VM boot-loader, when the interrupts are not yet enabled. They use a polling strategy on the block device status to detect completion.

=== 1) int '''_fat_sync_open'''( ) ===

=== 2) int '''_fat_sync_read'''( unsigned int fd_id  ,  unsigned int buffer  ,  unsigned int count  , unsigned int offset ) ===
This function transfer an integer number of blocks from an open file on the block device to a memory buffer, after checking the arguments.
If the number of requested sectors exceeds the file size, this number of sectors is reduced.
 * '''fd_id''' : file descriptor index
 * '''buffer''' : memory buffer virtual base address
 * '''count''' : number of blocks to transfer
 * '''offset''' : number of blocks to skip in file
Returns number of sectors transfered if success, returns -1 if error.

=== 3) int '''_fat_sync_ioc_access( unsigned int to_memory ,  unsigned int lba  ,  unsigned int buf_vaddr  ,  unsigned int count ) ===
This function computes the buffer physical address, and call the proper block device driver, as specified in the mapping.
 * '''to_memory''' : to memory transfer if non zero.
 * '''lba''' : first block index on the block device.
 * '''buf_vaddr''' : memory buffer virtual base address
 * '''count''' : number of blocks to transfer
Returns 0 if success, returns -1 if error.

== Interrupt based FAT32 access functions  ==