From: "Darrick J. Wong" Subject: [PATCH 13/13] crc32: Select an algorithm via kconfig Date: Wed, 18 Jan 2012 14:29:01 -0800 Message-ID: <20120118222901.4079.37238.stgit@elm3c44.beaverton.ibm.com> References: <20120118222733.4079.13377.stgit@elm3c44.beaverton.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Cc: Theodore Tso , Joakim Tjernlund , Bob Pearson , linux-kernel , Andreas Dilger , linux-crypto , linux-fsdevel , Mingming Cao , linux-ext4@vger.kernel.org To: Andrew Morton , Herbert Xu , "Darrick J. Wong" Return-path: In-Reply-To: <20120118222733.4079.13377.stgit@elm3c44.beaverton.ibm.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-crypto.vger.kernel.org Allow the kernel builder to choose a crc32* algorithm for the kernel. Signed-off-by: Darrick J. Wong --- lib/Kconfig | 43 +++++++++++++++++++++++++++++++++++++++++++ lib/crc32defs.h | 18 ++++++++++++++++++ 2 files changed, 61 insertions(+), 0 deletions(-) diff --git a/lib/Kconfig b/lib/Kconfig index 58da52d..13e1afa 100644 --- a/lib/Kconfig +++ b/lib/Kconfig @@ -77,6 +77,49 @@ 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.