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
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