kernel / pub / scm / linux / kernel / git / linusw / linux-gpio / refs/tags/gpio-v4.4-3 / . / include / linux / crc8.h

/* | |

* 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_ */ |