Commit 5cde7656 authored by Darrick J. Wong's avatar Darrick J. Wong Committed by Linus Torvalds
Browse files

crc32: select an algorithm via Kconfig 



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

Signed-off-by: default avatarDarrick J. Wong <djwong@us.ibm.com>
Cc: Bob Pearson <rpearson@systemfabricworks.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 577eba9e

lib/Kconfig

+43 −0
Original line number Diff line number Diff line
@@ -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

lib/crc32defs.h

+18 −0
Original line number Diff line number Diff line
@@ -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.