From: "Darrick J. Wong" Subject: [PATCH v5.1 4/4] crc32: Select an algorithm via kconfig Date: Sat, 8 Oct 2011 00:42:07 -0700 Message-ID: <20111008074207.GK12447@tux1.beaverton.ibm.com> References: <20111004235357.1560.12602.stgit@elm3c44.beaverton.ibm.com> <20111004235429.1560.89556.stgit@elm3c44.beaverton.ibm.com> Reply-To: djwong@us.ibm.com Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Joakim Tjernlund , Bob Pearson , linux-kernel , Mingming Cao , linux-crypto , linux-fsdevel , linux-ext4@vger.kernel.org To: Andreas Dilger , Herbert Xu , Theodore Tso , David Miller Return-path: Content-Disposition: inline In-Reply-To: <20111004235429.1560.89556.stgit@elm3c44.beaverton.ibm.com> Sender: linux-fsdevel-owner@vger.kernel.org List-Id: linux-ext4.vger.kernel.org Oops, the description of CRC32_SLICEBY4 is a bit screwy. Let's try that again. --- Allow the kernel builder to choose a crc32* algorithm for the kernel. Signed-off-by: Darrick J. Wong --- lib/Kconfig | 36 ++++++++++++++++++++++++++++++++++++ lib/crc32defs.h | 18 ++++++++++++++++++ 2 files changed, 54 insertions(+), 0 deletions(-) diff --git a/lib/Kconfig b/lib/Kconfig index 477be04..27881d9 100644 --- a/lib/Kconfig +++ b/lib/Kconfig @@ -70,6 +70,42 @@ 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 that this shouldn't be + a problem. + + If you don't know which to choose, choose this one. + +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. + +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. + +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. + +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.