/* * 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 … /* * 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) … /* required table size for crc8 algorithm */ #define CRC8_TABLE_SIZE … /* helper macro assuring right table size is used */ #define DECLARE_CRC8_TABLE(_table) … /** * 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], const u8 *pdata, size_t nbytes, u8 crc); #endif /* __CRC8_H_ */
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