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Diffstat (limited to 'include/linux/crc8.h')
-rw-r--r-- | include/linux/crc8.h | 101 |
1 files changed, 101 insertions, 0 deletions
diff --git a/include/linux/crc8.h b/include/linux/crc8.h new file mode 100644 index 000000000000..13c8dabb0441 --- /dev/null +++ b/include/linux/crc8.h | |||
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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_ */ | ||