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/crc8.h>
20 #include <linux/export.h>
21 #include <linux/module.h>
22 #include <linux/printk.h>
23
24 /**
25 * crc8_populate_msb - fill crc table for given polynomial in reverse bit order.
26 *
27 * @table: table to be filled.
28 * @polynomial: polynomial for which table is to be filled.
29 */
crc8_populate_msb(u8 table[CRC8_TABLE_SIZE],u8 polynomial)30 void crc8_populate_msb(u8 table[CRC8_TABLE_SIZE], u8 polynomial)
31 {
32 int i, j;
33 const u8 msbit = 0x80;
34 u8 t = msbit;
35
36 table[0] = 0;
37
38 for (i = 1; i < CRC8_TABLE_SIZE; i *= 2) {
39 t = (t << 1) ^ (t & msbit ? polynomial : 0);
40 for (j = 0; j < i; j++)
41 table[i+j] = table[j] ^ t;
42 }
43 }
44 EXPORT_SYMBOL(crc8_populate_msb);
45
46 /**
47 * crc8_populate_lsb - fill crc table for given polynomial in regular bit order.
48 *
49 * @table: table to be filled.
50 * @polynomial: polynomial for which table is to be filled.
51 */
crc8_populate_lsb(u8 table[CRC8_TABLE_SIZE],u8 polynomial)52 void crc8_populate_lsb(u8 table[CRC8_TABLE_SIZE], u8 polynomial)
53 {
54 int i, j;
55 u8 t = 1;
56
57 table[0] = 0;
58
59 for (i = (CRC8_TABLE_SIZE >> 1); i; i >>= 1) {
60 t = (t >> 1) ^ (t & 1 ? polynomial : 0);
61 for (j = 0; j < CRC8_TABLE_SIZE; j += 2*i)
62 table[i+j] = table[j] ^ t;
63 }
64 }
65 EXPORT_SYMBOL(crc8_populate_lsb);
66
67 /**
68 * crc8 - calculate a crc8 over the given input data.
69 *
70 * @table: crc table used for calculation.
71 * @pdata: pointer to data buffer.
72 * @nbytes: number of bytes in data buffer.
73 * @crc: previous returned crc8 value.
74 */
crc8(const u8 table[CRC8_TABLE_SIZE],const u8 * pdata,size_t nbytes,u8 crc)75 u8 crc8(const u8 table[CRC8_TABLE_SIZE], const u8 *pdata, size_t nbytes, u8 crc)
76 {
77 /* loop over the buffer data */
78 while (nbytes-- > 0)
79 crc = table[(crc ^ *pdata++) & 0xff];
80
81 return crc;
82 }
83 EXPORT_SYMBOL(crc8);
84
85 MODULE_DESCRIPTION("CRC8 (by Williams, Ross N.) function");
86 MODULE_AUTHOR("Broadcom Corporation");
87 MODULE_LICENSE("Dual BSD/GPL");
88