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Message-ID: <20120107055214.31315.46724.stgit@elm3c44.beaverton.ibm.com> Date: Fri, 06 Jan 2012 21:52:14 -0800 From: "Darrick J. Wong" <djwong@...ibm.com> To: Andrew Morton <akpm@...ux-foundation.org>, Herbert Xu <herbert@...dor.apana.org.au>, "Darrick J. Wong" <djwong@...ibm.com> Cc: Theodore Tso <tytso@....edu>, Joakim Tjernlund <joakim.tjernlund@...nsmode.se>, Bob Pearson <rpearson@...temfabricworks.com>, linux-kernel <linux-kernel@...r.kernel.org>, Andreas Dilger <adilger.kernel@...ger.ca>, linux-crypto <linux-crypto@...r.kernel.org>, linux-fsdevel <linux-fsdevel@...r.kernel.org>, Mingming Cao <cmm@...ibm.com>, linux-ext4@...r.kernel.org Subject: [PATCH 14/14] 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@...ibm.com> --- lib/Kconfig | 43 +++++++++++++++++++++++++++++++++++++++++++ lib/crc32defs.h | 18 ++++++++++++++++++ 2 files changed, 61 insertions(+), 0 deletions(-) diff --git a/lib/Kconfig b/lib/Kconfig index cfddafc..029c0e3 100644 --- a/lib/Kconfig +++ b/lib/Kconfig @@ -70,6 +70,49 @@ 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 diff --git a/lib/crc32defs.h b/lib/crc32defs.h index 6fd1917..64cba2c 100644 --- a/lib/crc32defs.h +++ b/lib/crc32defs.h @@ -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. -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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