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 | */ |

55 | void 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 | */ |

73 | void 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 | */ |

99 | u8 crc8(const u8 table[CRC8_TABLE_SIZE], u8 *pdata, size_t nbytes, u8 crc); |

100 | |

101 | #endif /* __CRC8_H_ */ |

102 |