101 lines
3.7 KiB
C
101 lines
3.7 KiB
C
/*
|
|
* 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_ */
|