From 7150962d637cf38617924f7f72ea00612283eb89 Mon Sep 17 00:00:00 2001 From: Arend van Spriel Date: Tue, 31 May 2011 11:22:15 +0200 Subject: lib: crc8: add new library module providing crc8 algorithm The brcm80211 driver in staging tree uses a crc8 function. Based on feedback from John Linville to move this to lib directory, the linux source has been searched. Although there is currently only one other kernel driver using this algorithm (ie. drivers/ssb) we are providing this as a library function for others to use. Cc: linux-kernel@vger.kernel.org Cc: linux-wireless@vger.kernel.org Cc: Dan Carpenter Cc: George Spelvin Cc: Randy Dunlap Reviewed-by: Henry Ptasinski Reviewed-by: Roland Vossen Reviewed-by: "Franky (Zhenhui) Lin" Signed-off-by: Arend van Spriel Signed-off-by: John W. Linville --- lib/crc8.c | 86 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 86 insertions(+) create mode 100644 lib/crc8.c (limited to 'lib/crc8.c') diff --git a/lib/crc8.c b/lib/crc8.c new file mode 100644 index 00000000000..87b59cafdb8 --- /dev/null +++ b/lib/crc8.c @@ -0,0 +1,86 @@ +/* + * Copyright (c) 2011 Broadcom Corporation + * + * Permission to use, copy, modify, and/or distribute this software for any + * purpose with or without fee is hereby granted, provided that the above + * copyright notice and this permission notice appear in all copies. + * + * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES + * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF + * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY + * SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES + * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION + * OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN + * CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. + */ + +#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt + +#include +#include +#include + +/* + * crc8_populate_msb - fill crc table for given polynomial in reverse bit order. + * + * table: table to be filled. + * polynomial: polynomial for which table is to be filled. + */ +void crc8_populate_msb(u8 table[CRC8_TABLE_SIZE], u8 polynomial) +{ + int i, j; + const u8 msbit = 0x80; + u8 t = msbit; + + table[0] = 0; + + for (i = 1; i < CRC8_TABLE_SIZE; i *= 2) { + t = (t << 1) ^ (t & msbit ? polynomial : 0); + for (j = 0; j < i; j++) + table[i+j] = table[j] ^ t; + } +} +EXPORT_SYMBOL(crc8_populate_msb); + +/* + * crc8_populate_lsb - fill crc table for given polynomial in regular bit order. + * + * table: table to be filled. + * polynomial: polynomial for which table is to be filled. + */ +void crc8_populate_lsb(u8 table[CRC8_TABLE_SIZE], u8 polynomial) +{ + int i, j; + u8 t = 1; + + table[0] = 0; + + for (i = (CRC8_TABLE_SIZE >> 1); i; i >>= 1) { + t = (t >> 1) ^ (t & 1 ? polynomial : 0); + for (j = 0; j < CRC8_TABLE_SIZE; j += 2*i) + table[i+j] = table[j] ^ t; + } +} +EXPORT_SYMBOL(crc8_populate_lsb); + +/* + * crc8 - calculate a crc8 over the given input data. + * + * table: crc table used for calculation. + * pdata: pointer to data buffer. + * nbytes: number of bytes in data buffer. + * crc: previous returned crc8 value. + */ +u8 crc8(const u8 table[CRC8_TABLE_SIZE], u8 *pdata, size_t nbytes, u8 crc) +{ + /* loop over the buffer data */ + while (nbytes-- > 0) + crc = table[(crc ^ *pdata++) & 0xff]; + + return crc; +} +EXPORT_SYMBOL(crc8); + +MODULE_DESCRIPTION("CRC8 (by Williams, Ross N.) function"); +MODULE_AUTHOR("Broadcom Corporation"); +MODULE_LICENSE("Dual BSD/GPL"); -- cgit v1.2.3