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 | |
17 | #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt |
18 | |
19 | #include <linux/module.h> |
20 | #include <linux/crc8.h> |
21 | #include <linux/printk.h> |
22 | |
23 | /** |
24 | * crc8_populate_msb - fill crc table for given polynomial in reverse bit order. |
25 | * |
26 | * @table: table to be filled. |
27 | * @polynomial: polynomial for which table is to be filled. |
28 | */ |
29 | void crc8_populate_msb(u8 table[CRC8_TABLE_SIZE], u8 polynomial) |
30 | { |
31 | int i, j; |
32 | const u8 msbit = 0x80; |
33 | u8 t = msbit; |
34 | |
35 | table[0] = 0; |
36 | |
37 | for (i = 1; i < CRC8_TABLE_SIZE; i *= 2) { |
38 | t = (t << 1) ^ (t & msbit ? polynomial : 0); |
39 | for (j = 0; j < i; j++) |
40 | table[i+j] = table[j] ^ t; |
41 | } |
42 | } |
43 | EXPORT_SYMBOL(crc8_populate_msb); |
44 | |
45 | /** |
46 | * crc8_populate_lsb - fill crc table for given polynomial in regular bit order. |
47 | * |
48 | * @table: table to be filled. |
49 | * @polynomial: polynomial for which table is to be filled. |
50 | */ |
51 | void crc8_populate_lsb(u8 table[CRC8_TABLE_SIZE], u8 polynomial) |
52 | { |
53 | int i, j; |
54 | u8 t = 1; |
55 | |
56 | table[0] = 0; |
57 | |
58 | for (i = (CRC8_TABLE_SIZE >> 1); i; i >>= 1) { |
59 | t = (t >> 1) ^ (t & 1 ? polynomial : 0); |
60 | for (j = 0; j < CRC8_TABLE_SIZE; j += 2*i) |
61 | table[i+j] = table[j] ^ t; |
62 | } |
63 | } |
64 | EXPORT_SYMBOL(crc8_populate_lsb); |
65 | |
66 | /** |
67 | * crc8 - calculate a crc8 over the given input data. |
68 | * |
69 | * @table: crc table used for calculation. |
70 | * @pdata: pointer to data buffer. |
71 | * @nbytes: number of bytes in data buffer. |
72 | * @crc: previous returned crc8 value. |
73 | */ |
74 | u8 crc8(const u8 table[CRC8_TABLE_SIZE], const u8 *pdata, size_t nbytes, u8 crc) |
75 | { |
76 | /* loop over the buffer data */ |
77 | while (nbytes-- > 0) |
78 | crc = table[(crc ^ *pdata++) & 0xff]; |
79 | |
80 | return crc; |
81 | } |
82 | EXPORT_SYMBOL(crc8); |
83 | |
84 | MODULE_DESCRIPTION("CRC8 (by Williams, Ross N.) function" ); |
85 | MODULE_AUTHOR("Broadcom Corporation" ); |
86 | MODULE_LICENSE("Dual BSD/GPL" ); |
87 | |