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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_ */ |