229 lines
9.4 KiB
Plaintext
229 lines
9.4 KiB
Plaintext
#
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# For a description of the syntax of this configuration file,
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# see the file kconfig-language.txt in the NuttX tools repository.
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#
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config FS_FAT
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bool "FAT file system"
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default n
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depends on !DISABLE_MOUNTPOINT
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---help---
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Enable FAT filesystem support
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if FS_FAT
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config FAT_COMPUTE_FSINFO
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bool "FAT compute free space in FSINFO at mount time"
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default n
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---help---
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Enables the computation of free clusters at mount time as suggested by the
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white paper for FAT. The standard behavior of NuttX is to trust the stored
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value and only recompute it once required. This works if the file system
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is never mounted to another OS. SD-cards which are mounted to Windows to
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modify the content might report wrong space after reinserting it to NuttX.
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It is recommended to activate this setting if the "SD-Card" is swapped
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between systems.
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config FAT_LCNAMES
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bool "FAT upper/lower names"
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default n
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---help---
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Enable use of the NT-style upper/lower case 8.3
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file name support.
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config FAT_LFN
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bool "FAT long file names"
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default n
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---help---
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Enable FAT long file names. NOTE: Microsoft claims
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patents on FAT long file name technology. Please read the
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disclaimer in the top-level NOTICE file and only enable this
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feature if you understand these issues.
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config FAT_MAXFNAME
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int "FAT maximum file name size"
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depends on FAT_LFN
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default NAME_MAX
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range 12 255
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---help---
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If FAT_LFN is defined, then the default, maximum long file
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name is 255 bytes. This can eat up a lot of memory (especially stack
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space). If you are willing to live with some non-standard, short long
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file names, then define this value to be something more reasonable. A
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good choice would be the same value as selected for NAME_MAX which will
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limit the visibility of longer file names anyway.
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This setting may not exceed NAME_MAX. That will be verified at compile
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time. The minimum values is 12 due to assumptions in internal logic.
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config FAT_LFN_ALIAS_HASH
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bool "Use faster method for forming long filename 8.3 alias"
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depends on FAT_LFN
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default n
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---help---
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Long filenames on FAT filesystems have associated 8.3 character alias
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short filenames. The traditional form of these is FILENA~1.EXT with
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a running count of the number of similar names. However creating this
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unique count can take several seconds if there are many similarly named
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files in the directory. Enabling FAT_LFN_ALIAS_HASH uses an alternative
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format of FI0123~1.TXT where the four digits are a hash of the original
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filename. This method is similar to what is used by Windows 2000 and
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later.
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config FAT_LFN_UTF8
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bool "Allow UTF8 long filenames"
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depends on FAT_LFN
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default n
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---help---
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UTF8 long filenames are accepted and converted to UCS2.
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config FAT_LFN_ALIAS_TRAILCHARS
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int "Number of trailing characters to use for 8.3 alias"
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depends on FAT_LFN
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default 0
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---help---
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Traditional format for long filename 8.3 aliases takes first 6
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characters of long filename. If this option is set to N > 0,
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NuttX will instead take first 6-N and last N characters to form
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the short name. This is useful for filenames like "datafile12.txt"
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where the first characters would always remain the same.
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config FS_FATTIME
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bool "FAT timestamps"
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default n
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---help---
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Support FAT date and time. NOTE: There is not
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much sense in supporting FAT date and time unless you have a
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hardware RTC or other way to get the time and date.
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config FAT_FORCE_INDIRECT
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bool "Force direct transfers"
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default n
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---help---
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Normally, the default behavior for the FAT file system is to perform
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data transfers indirectly though specially allocated sector buffers
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or, under certain circumstances, directly through user provided
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buffers . These circumstances are: (1) The transfer is being
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performed from the beginning of a sector (2) the user-provided
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buffer will hold the full sector of data.
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Some hardware, however, may require special DMA-capable memory or
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specially aligned memory in order to perform the transfers. In this
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case, there may be no circumstance where the user buffer can be used.
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Selecting this option will disable all attempts to use the user-
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provided buffer: All transfers will be force to be performed
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indirectly through the FAT file systems sector buffers.
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Note: This will have the negative impact of: (1) An extra data
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copy to transfer the data between the user buffer and the FAT file
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systems internal sector buffers, and (2) A loss of performance
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because I/O will be limited to one sector at a time.
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This would typically be used with CONFIG_FAT_DMAMEMORY so that
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special memory allocators are also used and transfers are also
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performed using only that specially allocated memory.
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CONFIG_FAT_DMAMEMORY, on the other hand, is often used without
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CONFIG_FAT_FORCE_INDIRECT when the user memory buffers may come
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from mixed locations, some of which are DMA-able and some of
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which are not. But CONFIG_FAT_FORCE_INDIRECT could be used
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without CONFIG_FAT_DMAMEMORY if there is, for example, only a
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memory alignment constraints.
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FORCE_ DMA DIRECT EXAMPLE USAGE
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INDIRECT MEMORY RETRY
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Y Y * Use specially allocated memory;
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Never use caller provided buffer
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Y N * Not recommended
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N Y ** Special memory required; user memory
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has mixed capability; sometimes
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caller memory is not usable
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N N Y No special memory but there are
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alignment requirements; return is
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caller buffer is not properly aligned
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N N N User memory can always be used for
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transfer.
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* CONFIG_DIRECT_RETRY cannot be selected with CONFIG_FORCE_INDIRECT
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** CONFIG_DIRECT_RETRY is automatically selected with CONFIG_DMA_MEMORY
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config FAT_DMAMEMORY
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bool "DMA memory allocator"
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default n
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select FAT_DIRECT_RETRY if !FAT_FORCE_INDIRECT
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---help---
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The FAT file system allocates two I/O buffers for data transfer, each
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are the size of one device sector. One of the buffers is allocated
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once for each FAT volume that is mounted; the other buffers are
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allocated each time a FAT file is opened.
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Some hardware, however, may require special DMA-capable memory in
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order to perform the transfers. If FAT_DMAMEMORY is defined
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then the architecture-specific hardware must provide the functions
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fat_dma_alloc() and fat_dma_free(): fat_dmalloc() will allocate
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DMA-capable memory of the specified size; fat_dmafree() is the
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corresponding function that will be called to free the DMA-capable
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memory.
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FORCE_ DMA DIRECT EXAMPLE USAGE
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INDIRECT MEMORY RETRY
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Y Y * Use specially allocated memory;
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Never use caller provided buffer
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Y N * Not recommended
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N Y ** Special memory required; user memory
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has mixed capability; sometimes
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caller memory is not usable
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N N Y No special memory but there are
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alignment requirements; return is
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caller buffer is not properly aligned
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N N N User memory can always be used for
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transfer.
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* CONFIG_DIRECT_RETRY cannot be selected with CONFIG_FORCE_INDIRECT
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** CONFIG_DIRECT_RETRY is automatically selected with CONFIG_DMA_MEMORY
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config FAT_DIRECT_RETRY
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bool "Direct transfer retry"
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default FAT_DMAMEMORY
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depends on !FAT_FORCE_INDIRECT
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---help---
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The FAT file system contains internal, well aligned sector buffers
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for indirect data transfer. These transfers are indirect in the
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sense that that the actual transfer occurs into/out of the sector
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buffers and an additional copy is necessary to/from the user-
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provided I/O buffers. But under certain conditions, the FAT file
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system will use the caller-provided I/O buffers directly to improve
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efficiency. Those conditions are (1) CONFIG_FAT_FORCE_INDIRECT is
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not defined, (2) The access is to/from the beginning of a sector,
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and (3) the user provided buffer is large enough to hold an entire
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sector.
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The lower level SDIO driver may have, certain requirements on the
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memory buffer in order to perform the transfer. Perhaps special
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DMA memory should be used (with CONFIG_FAT_DMAMEMORY) or perhaps
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some special memory alignment is required to interface with the
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hardware.
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If this option is selected, then the FAT file system will first
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try the user provided I/O buffer under above conditions. If the
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transfer fails with -EFAULT. then the FAT file system will try one
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more time using the internal sector buffers.
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FORCE_ DMA DIRECT EXAMPLE USAGE
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INDIRECT MEMORY RETRY
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Y Y * Use specially allocated memory;
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Never use caller provided buffer
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Y N * Not recommended
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N Y ** Special memory required; user memory
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has mixed capability; sometimes
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caller memory is not usable
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N N Y No special memory but there are
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alignment requirements; return is
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caller buffer is not properly aligned
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N N N User memory can always be used for
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transfer.
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* CONFIG_DIRECT_RETRY cannot be selected with CONFIG_FORCE_INDIRECT
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** CONFIG_DIRECT_RETRY is automatically selected with CONFIG_DMA_MEMORY
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endif # FAT
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