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To assign a cache heap use:
{ ADI_FSS_CMD_SET_CACHE_HEAP_ID, (void*)CacheHeap },
which can be added to the configuration table of each driver and the
adi_fss_Init()
index for allocation of each file cache buffer. See
page 12-17
for further details.
The default case is for all cache heaps to default to the general heap, and
the general heap to default to the system heap. This is the case for the con-
figuration shown in
while it is perfectly valid to use the same cache heap index for each driver
(FSD or PID), the heap index is required to be registered with each device
driver through its configuration table.
File Cache
The file system service is designed to use a file cache when appropriate.
This cache, which is allocated from the FSS cache heap,
ory Usage" on page
to enhance data transfer rates in either direction. To achieve higher trans-
fer rates, cache blocks are transferred to or from the media in the
background, and its use is thus optimal for physical interface drivers that
use peripheral DMA. The decision to use a file cache for a file is taken by
the FSS upon opening a file, when the respective file system driver and
physical interface drivers are queried to determine whether a file cache can
be supported. Please refer to the appropriate FSD and PID documentation
for details. For example, the FAT and ATAPI drivers for access to the hard
disk on the ADSP-BF548 EZ-KIT Lite support the use of a file cache.
Each file cache comprises a number of blocks, each the size of the smallest
addressable unit within the respective file system. For example, in the FAT
file system, the block size is that of a cluster. The cluster size depends on
the size and format (for example, FAT12, FAT16 or FAT32) of the media.
The FSS requests the block size from the appropriate FSD upon opening a
VisualDSP++ 5.0 Device Drivers and System
Services Manual for Blackfin Processors
function. In the latter case, it is used to assign the heap
"Getting Started" on page
12-14), acts as a read-ahead, write-behind cache so as
File System Service
"File Cache" on
12-3. Please note that
("Dynamic Mem-
12-17
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