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Diffstat (limited to 'include/compat/linux/crc8.h')
-rwxr-xr-x | include/compat/linux/crc8.h | 101 |
1 files changed, 101 insertions, 0 deletions
diff --git a/include/compat/linux/crc8.h b/include/compat/linux/crc8.h new file mode 100755 index 0000000..13c8dab --- /dev/null +++ b/include/compat/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_ */ |