linux/include/linux/crc8.h
<<
>>
Prefs
   1/*
   2 * Copyright (c) 2011 Broadcom Corporation
   3 *
   4 * Permission to use, copy, modify, and/or distribute this software for any
   5 * purpose with or without fee is hereby granted, provided that the above
   6 * copyright notice and this permission notice appear in all copies.
   7 *
   8 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
   9 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
  10 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
  11 * SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
  12 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
  13 * OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
  14 * CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
  15 */
  16#ifndef __CRC8_H_
  17#define __CRC8_H_
  18
  19#include <linux/types.h>
  20
  21/* see usage of this value in crc8() description */
  22#define CRC8_INIT_VALUE         0xFF
  23
  24/*
  25 * Return value of crc8() indicating valid message+crc. This is true
  26 * if a CRC is inverted before transmission. The CRC computed over the
  27 * whole received bitstream is _table[x], where x is the bit pattern
  28 * of the modification (almost always 0xff).
  29 */
  30#define CRC8_GOOD_VALUE(_table) (_table[0xFF])
  31
  32/* required table size for crc8 algorithm */
  33#define CRC8_TABLE_SIZE                 256
  34
  35/* helper macro assuring right table size is used */
  36#define DECLARE_CRC8_TABLE(_table) \
  37        static u8 _table[CRC8_TABLE_SIZE]
  38
  39/**
  40 * crc8_populate_lsb - fill crc table for given polynomial in regular bit order.
  41 *
  42 * @table:      table to be filled.
  43 * @polynomial: polynomial for which table is to be filled.
  44 *
  45 * This function fills the provided table according the polynomial provided for
  46 * regular bit order (lsb first). Polynomials in CRC algorithms are typically
  47 * represented as shown below.
  48 *
  49 *      poly = x^8 + x^7 + x^6 + x^4 + x^2 + 1
  50 *
  51 * For lsb first direction x^7 maps to the lsb. So the polynomial is as below.
  52 *
  53 * - lsb first: poly = 10101011(1) = 0xAB
  54 */
  55void crc8_populate_lsb(u8 table[CRC8_TABLE_SIZE], u8 polynomial);
  56
  57/**
  58 * crc8_populate_msb - fill crc table for given polynomial in reverse bit order.
  59 *
  60 * @table:      table to be filled.
  61 * @polynomial: polynomial for which table is to be filled.
  62 *
  63 * This function fills the provided table according the polynomial provided for
  64 * reverse bit order (msb first). Polynomials in CRC algorithms are typically
  65 * represented as shown below.
  66 *
  67 *      poly = x^8 + x^7 + x^6 + x^4 + x^2 + 1
  68 *
  69 * For msb first direction x^7 maps to the msb. So the polynomial is as below.
  70 *
  71 * - msb first: poly = (1)11010101 = 0xD5
  72 */
  73void crc8_populate_msb(u8 table[CRC8_TABLE_SIZE], u8 polynomial);
  74
  75/**
  76 * crc8() - calculate a crc8 over the given input data.
  77 *
  78 * @table:      crc table used for calculation.
  79 * @pdata:      pointer to data buffer.
  80 * @nbytes:     number of bytes in data buffer.
  81 * @crc:        previous returned crc8 value.
  82 *
  83 * The CRC8 is calculated using the polynomial given in crc8_populate_msb()
  84 * or crc8_populate_lsb().
  85 *
  86 * The caller provides the initial value (either %CRC8_INIT_VALUE
  87 * or the previous returned value) to allow for processing of
  88 * discontiguous blocks of data.  When generating the CRC the
  89 * caller is responsible for complementing the final return value
  90 * and inserting it into the byte stream.  When validating a byte
  91 * stream (including CRC8), a final return value of %CRC8_GOOD_VALUE
  92 * indicates the byte stream data can be considered valid.
  93 *
  94 * Reference:
  95 * "A Painless Guide to CRC Error Detection Algorithms", ver 3, Aug 1993
  96 * Williams, Ross N., ross<at>ross.net
  97 * (see URL http://www.ross.net/crc/download/crc_v3.txt).
  98 */
  99u8 crc8(const u8 table[CRC8_TABLE_SIZE], u8 *pdata, size_t nbytes, u8 crc);
 100
 101#endif /* __CRC8_H_ */
 102
lxr.linux.no kindly hosted by Redpill Linpro AS, provider of Linux consulting and operations services since 1995.