1 /* 2 * crc7.c 3 * 4 * This source code is licensed under the GNU General Public License, 5 * Version 2. See the file COPYING for more details. 6 */ 7 8 #include <linux/types.h> 9 #include <linux/module.h> 10 #include <linux/crc7.h> 11 12 13 /* 14 * Table for CRC-7 (polynomial x^7 + x^3 + 1). 15 * This is a big-endian CRC (msbit is highest power of x), 16 * aligned so the msbit of the byte is the x^6 coefficient 17 * and the lsbit is not used. 18 */ 19 const u8 crc7_be_syndrome_table[256] = { 20 0x00, 0x12, 0x24, 0x36, 0x48, 0x5a, 0x6c, 0x7e, 21 0x90, 0x82, 0xb4, 0xa6, 0xd8, 0xca, 0xfc, 0xee, 22 0x32, 0x20, 0x16, 0x04, 0x7a, 0x68, 0x5e, 0x4c, 23 0xa2, 0xb0, 0x86, 0x94, 0xea, 0xf8, 0xce, 0xdc, 24 0x64, 0x76, 0x40, 0x52, 0x2c, 0x3e, 0x08, 0x1a, 25 0xf4, 0xe6, 0xd0, 0xc2, 0xbc, 0xae, 0x98, 0x8a, 26 0x56, 0x44, 0x72, 0x60, 0x1e, 0x0c, 0x3a, 0x28, 27 0xc6, 0xd4, 0xe2, 0xf0, 0x8e, 0x9c, 0xaa, 0xb8, 28 0xc8, 0xda, 0xec, 0xfe, 0x80, 0x92, 0xa4, 0xb6, 29 0x58, 0x4a, 0x7c, 0x6e, 0x10, 0x02, 0x34, 0x26, 30 0xfa, 0xe8, 0xde, 0xcc, 0xb2, 0xa0, 0x96, 0x84, 31 0x6a, 0x78, 0x4e, 0x5c, 0x22, 0x30, 0x06, 0x14, 32 0xac, 0xbe, 0x88, 0x9a, 0xe4, 0xf6, 0xc0, 0xd2, 33 0x3c, 0x2e, 0x18, 0x0a, 0x74, 0x66, 0x50, 0x42, 34 0x9e, 0x8c, 0xba, 0xa8, 0xd6, 0xc4, 0xf2, 0xe0, 35 0x0e, 0x1c, 0x2a, 0x38, 0x46, 0x54, 0x62, 0x70, 36 0x82, 0x90, 0xa6, 0xb4, 0xca, 0xd8, 0xee, 0xfc, 37 0x12, 0x00, 0x36, 0x24, 0x5a, 0x48, 0x7e, 0x6c, 38 0xb0, 0xa2, 0x94, 0x86, 0xf8, 0xea, 0xdc, 0xce, 39 0x20, 0x32, 0x04, 0x16, 0x68, 0x7a, 0x4c, 0x5e, 40 0xe6, 0xf4, 0xc2, 0xd0, 0xae, 0xbc, 0x8a, 0x98, 41 0x76, 0x64, 0x52, 0x40, 0x3e, 0x2c, 0x1a, 0x08, 42 0xd4, 0xc6, 0xf0, 0xe2, 0x9c, 0x8e, 0xb8, 0xaa, 43 0x44, 0x56, 0x60, 0x72, 0x0c, 0x1e, 0x28, 0x3a, 44 0x4a, 0x58, 0x6e, 0x7c, 0x02, 0x10, 0x26, 0x34, 45 0xda, 0xc8, 0xfe, 0xec, 0x92, 0x80, 0xb6, 0xa4, 46 0x78, 0x6a, 0x5c, 0x4e, 0x30, 0x22, 0x14, 0x06, 47 0xe8, 0xfa, 0xcc, 0xde, 0xa0, 0xb2, 0x84, 0x96, 48 0x2e, 0x3c, 0x0a, 0x18, 0x66, 0x74, 0x42, 0x50, 49 0xbe, 0xac, 0x9a, 0x88, 0xf6, 0xe4, 0xd2, 0xc0, 50 0x1c, 0x0e, 0x38, 0x2a, 0x54, 0x46, 0x70, 0x62, 51 0x8c, 0x9e, 0xa8, 0xba, 0xc4, 0xd6, 0xe0, 0xf2 52 }; 53 EXPORT_SYMBOL(crc7_be_syndrome_table); 54 55 /** 56 * crc7 - update the CRC7 for the data buffer 57 * @crc: previous CRC7 value 58 * @buffer: data pointer 59 * @len: number of bytes in the buffer 60 * Context: any 61 * 62 * Returns the updated CRC7 value. 63 * The CRC7 is left-aligned in the byte (the lsbit is always 0), as that 64 * makes the computation easier, and all callers want it in that form. 65 * 66 */ 67 u8 crc7_be(u8 crc, const u8 *buffer, size_t len) 68 { 69 while (len--) 70 crc = crc7_be_byte(crc, *buffer++); 71 return crc; 72 } 73 EXPORT_SYMBOL(crc7_be); 74 75 MODULE_DESCRIPTION("CRC7 calculations"); 76 MODULE_LICENSE("GPL"); 77