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crc32: select an algorithm via Kconfig 

Allow the kernel builder to choose a crc32* algorithm for the kernel.

Signed-off-by: Darrick J. Wong <djwong@us.ibm.com>
Cc: Bob Pearson <rpearson@systemfabricworks.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Darrick J. Wong 2012-03-23 15:02:26 -07:00 committed by Linus Torvalds
parent 577eba9e22
commit 5cde7656d0
2 changed files with 61 additions and 0 deletions
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43
lib/Kconfig
View File

@ -80,6 +80,49 @@ config CRC32_SELFTEST
and crc32_be over byte strings with random alignment and length
and computes the total elapsed time and number of bytes processed.
choice
prompt "CRC32 implementation"
depends on CRC32
default CRC32_SLICEBY8
config CRC32_SLICEBY8
bool "Slice by 8 bytes"
help
Calculate checksum 8 bytes at a time with a clever slicing algorithm.
This is the fastest algorithm, but comes with a 8KiB lookup table.
Most modern processors have enough cache to hold this table without
thrashing the cache.
This is the default implementation choice. Choose this one unless
you have a good reason not to.
config CRC32_SLICEBY4
bool "Slice by 4 bytes"
help
Calculate checksum 4 bytes at a time with a clever slicing algorithm.
This is a bit slower than slice by 8, but has a smaller 4KiB lookup
table.
Only choose this option if you know what you are doing.
config CRC32_SARWATE
bool "Sarwate's Algorithm (one byte at a time)"
help
Calculate checksum a byte at a time using Sarwate's algorithm. This
is not particularly fast, but has a small 256 byte lookup table.
Only choose this option if you know what you are doing.
config CRC32_BIT
bool "Classic Algorithm (one bit at a time)"
help
Calculate checksum one bit at a time. This is VERY slow, but has
no lookup table. This is provided as a debugging option.
Only choose this option if you are debugging crc32.
endchoice
config CRC7
tristate "CRC7 functions"
help

18
lib/crc32defs.h
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@ -13,6 +13,24 @@
*/
#define CRC32C_POLY_LE 0x82F63B78
/* Try to choose an implementation variant via Kconfig */
#ifdef CONFIG_CRC32_SLICEBY8
# define CRC_LE_BITS 64
# define CRC_BE_BITS 64
#endif
#ifdef CONFIG_CRC32_SLICEBY4
# define CRC_LE_BITS 32
# define CRC_BE_BITS 32
#endif
#ifdef CONFIG_CRC32_SARWATE
# define CRC_LE_BITS 8
# define CRC_BE_BITS 8
#endif
#ifdef CONFIG_CRC32_BIT
# define CRC_LE_BITS 1
# define CRC_BE_BITS 1
#endif
/*
* How many bits at a time to use. Valid values are 1, 2, 4, 8, 32 and 64.
* For less performance-sensitive, use 4 or 8 to save table size.