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