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