diff options
| -rw-r--r-- | include/linux/crc8.h | 101 | ||||
| -rw-r--r-- | lib/Kconfig | 7 | ||||
| -rw-r--r-- | lib/Makefile | 1 | ||||
| -rw-r--r-- | lib/crc8.c | 86 |
4 files changed, 195 insertions, 0 deletions
diff --git a/include/linux/crc8.h b/include/linux/crc8.h new file mode 100644 index 0000000..13c8dab --- /dev/null +++ b/include/linux/crc8.h @@ -0,0 +1,101 @@ +/* + * 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. + */ +#ifndef __CRC8_H_ +#define __CRC8_H_ + +#include <linux/types.h> + +/* see usage of this value in crc8() description */ +#define CRC8_INIT_VALUE 0xFF + +/* + * Return value of crc8() indicating valid message+crc. This is true + * if a CRC is inverted before transmission. The CRC computed over the + * whole received bitstream is _table[x], where x is the bit pattern + * of the modification (almost always 0xff). + */ +#define CRC8_GOOD_VALUE(_table) (_table[0xFF]) + +/* required table size for crc8 algorithm */ +#define CRC8_TABLE_SIZE 256 + +/* helper macro assuring right table size is used */ +#define DECLARE_CRC8_TABLE(_table) \ + static u8 _table[CRC8_TABLE_SIZE] + +/** + * 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. + * + * This function fills the provided table according the polynomial provided for + * regular bit order (lsb first). Polynomials in CRC algorithms are typically + * represented as shown below. + * + * poly = x^8 + x^7 + x^6 + x^4 + x^2 + 1 + * + * For lsb first direction x^7 maps to the lsb. So the polynomial is as below. + * + * - lsb first: poly = 10101011(1) = 0xAB + */ +void crc8_populate_lsb(u8 table[CRC8_TABLE_SIZE], u8 polynomial); + +/** + * 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. + * + * This function fills the provided table according the polynomial provided for + * reverse bit order (msb first). Polynomials in CRC algorithms are typically + * represented as shown below. + * + * poly = x^8 + x^7 + x^6 + x^4 + x^2 + 1 + * + * For msb first direction x^7 maps to the msb. So the polynomial is as below. + * + * - msb first: poly = (1)11010101 = 0xD5 + */ +void crc8_populate_msb(u8 table[CRC8_TABLE_SIZE], u8 polynomial); + +/** + * 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. + * + * The CRC8 is calculated using the polynomial given in crc8_populate_msb() + * or crc8_populate_lsb(). + * + * The caller provides the initial value (either %CRC8_INIT_VALUE + * or the previous returned value) to allow for processing of + * discontiguous blocks of data. When generating the CRC the + * caller is responsible for complementing the final return value + * and inserting it into the byte stream. When validating a byte + * stream (including CRC8), a final return value of %CRC8_GOOD_VALUE + * indicates the byte stream data can be considered valid. + * + * Reference: + * "A Painless Guide to CRC Error Detection Algorithms", ver 3, Aug 1993 + * Williams, Ross N., ross<at>ross.net + * (see URL http://www.ross.net/crc/download/crc_v3.txt). + */ +u8 crc8(const u8 table[CRC8_TABLE_SIZE], u8 *pdata, size_t nbytes, u8 crc); + +#endif /* __CRC8_H_ */ diff --git a/lib/Kconfig b/lib/Kconfig index 9c10e38..ff9e5a3 100644 --- a/lib/Kconfig +++ b/lib/Kconfig @@ -89,6 +89,13 @@ config LIBCRC32C require M here. See Castagnoli93. Module will be libcrc32c. +config CRC8 + tristate "CRC8 function" + help + This option provides CRC8 function. Drivers may select this + when they need to do cyclic redundancy check according CRC8 + algorithm. Module will be called crc8. + config AUDIT_GENERIC bool depends on AUDIT && !AUDIT_ARCH diff --git a/lib/Makefile b/lib/Makefile index 4b49a24..704959d 100644 --- a/lib/Makefile +++ b/lib/Makefile @@ -65,6 +65,7 @@ obj-$(CONFIG_CRC_ITU_T) += crc-itu-t.o obj-$(CONFIG_CRC32) += crc32.o obj-$(CONFIG_CRC7) += crc7.o obj-$(CONFIG_LIBCRC32C) += libcrc32c.o +obj-$(CONFIG_CRC8) += crc8.o obj-$(CONFIG_GENERIC_ALLOCATOR) += genalloc.o obj-$(CONFIG_ZLIB_INFLATE) += zlib_inflate/ diff --git a/lib/crc8.c b/lib/crc8.c new file mode 100644 index 0000000..87b59ca --- /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 <linux/module.h> +#include <linux/crc8.h> +#include <linux/printk.h> + +/* + * 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"); |
