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crc32: select an algorithm via Kconfig

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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 crc32_be over byte strings with random alignment and length
and computes the total elapsed time and number of bytes processed. 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 config CRC7
tristate "CRC7 functions" tristate "CRC7 functions"
help help

18
lib/crc32defs.h
View file

@ -13,6 +13,24 @@
*/ */
#define CRC32C_POLY_LE 0x82F63B78 #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. * 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. * For less performance-sensitive, use 4 or 8 to save table size.