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lib: add crc7 from Linux

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Crc7 is used to compute mmc spi command packet checksum.

Copy from linux-2.6 lib/crc7.c include/linux/crc7.h
commit ad241528c4919505afccb022acbab3eeb0db4d80

Signed-off-by: Thomas Chou <thomas@wytron.com.tw>
This commit is contained in:
Thomas Chou 2011-01-11 09:38:20 +08:00 committed by Wolfgang Denk
parent 5c4fa2eea0
commit ed6ce67a2c
3 changed files with 77 additions and 0 deletions
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14
include/linux/crc7.h Normal file
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@ -0,0 +1,14 @@
#ifndef _LINUX_CRC7_H
#define _LINUX_CRC7_H
#include <linux/types.h>
extern const u8 crc7_syndrome_table[256];
static inline u8 crc7_byte(u8 crc, u8 data)
{
return crc7_syndrome_table[(crc << 1) ^ data];
}
extern u8 crc7(u8 crc, const u8 *buffer, size_t len);
#endif

1
lib/Makefile
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@ -32,6 +32,7 @@ COBJS-$(CONFIG_BZIP2) += bzlib_decompress.o
COBJS-$(CONFIG_BZIP2) += bzlib_randtable.o
COBJS-$(CONFIG_BZIP2) += bzlib_huffman.o
COBJS-$(CONFIG_USB_TTY) += circbuf.o
COBJS-y += crc7.o
COBJS-y += crc16.o
COBJS-y += crc32.o
COBJS-y += ctype.o

62
lib/crc7.c Normal file
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@ -0,0 +1,62 @@
/*
* crc7.c
*
* This source code is licensed under the GNU General Public License,
* Version 2. See the file COPYING for more details.
*/
#include <linux/types.h>
#include <linux/crc7.h>
/* Table for CRC-7 (polynomial x^7 + x^3 + 1) */
const u8 crc7_syndrome_table[256] = {
0x00, 0x09, 0x12, 0x1b, 0x24, 0x2d, 0x36, 0x3f,
0x48, 0x41, 0x5a, 0x53, 0x6c, 0x65, 0x7e, 0x77,
0x19, 0x10, 0x0b, 0x02, 0x3d, 0x34, 0x2f, 0x26,
0x51, 0x58, 0x43, 0x4a, 0x75, 0x7c, 0x67, 0x6e,
0x32, 0x3b, 0x20, 0x29, 0x16, 0x1f, 0x04, 0x0d,
0x7a, 0x73, 0x68, 0x61, 0x5e, 0x57, 0x4c, 0x45,
0x2b, 0x22, 0x39, 0x30, 0x0f, 0x06, 0x1d, 0x14,
0x63, 0x6a, 0x71, 0x78, 0x47, 0x4e, 0x55, 0x5c,
0x64, 0x6d, 0x76, 0x7f, 0x40, 0x49, 0x52, 0x5b,
0x2c, 0x25, 0x3e, 0x37, 0x08, 0x01, 0x1a, 0x13,
0x7d, 0x74, 0x6f, 0x66, 0x59, 0x50, 0x4b, 0x42,
0x35, 0x3c, 0x27, 0x2e, 0x11, 0x18, 0x03, 0x0a,
0x56, 0x5f, 0x44, 0x4d, 0x72, 0x7b, 0x60, 0x69,
0x1e, 0x17, 0x0c, 0x05, 0x3a, 0x33, 0x28, 0x21,
0x4f, 0x46, 0x5d, 0x54, 0x6b, 0x62, 0x79, 0x70,
0x07, 0x0e, 0x15, 0x1c, 0x23, 0x2a, 0x31, 0x38,
0x41, 0x48, 0x53, 0x5a, 0x65, 0x6c, 0x77, 0x7e,
0x09, 0x00, 0x1b, 0x12, 0x2d, 0x24, 0x3f, 0x36,
0x58, 0x51, 0x4a, 0x43, 0x7c, 0x75, 0x6e, 0x67,
0x10, 0x19, 0x02, 0x0b, 0x34, 0x3d, 0x26, 0x2f,
0x73, 0x7a, 0x61, 0x68, 0x57, 0x5e, 0x45, 0x4c,
0x3b, 0x32, 0x29, 0x20, 0x1f, 0x16, 0x0d, 0x04,
0x6a, 0x63, 0x78, 0x71, 0x4e, 0x47, 0x5c, 0x55,
0x22, 0x2b, 0x30, 0x39, 0x06, 0x0f, 0x14, 0x1d,
0x25, 0x2c, 0x37, 0x3e, 0x01, 0x08, 0x13, 0x1a,
0x6d, 0x64, 0x7f, 0x76, 0x49, 0x40, 0x5b, 0x52,
0x3c, 0x35, 0x2e, 0x27, 0x18, 0x11, 0x0a, 0x03,
0x74, 0x7d, 0x66, 0x6f, 0x50, 0x59, 0x42, 0x4b,
0x17, 0x1e, 0x05, 0x0c, 0x33, 0x3a, 0x21, 0x28,
0x5f, 0x56, 0x4d, 0x44, 0x7b, 0x72, 0x69, 0x60,
0x0e, 0x07, 0x1c, 0x15, 0x2a, 0x23, 0x38, 0x31,
0x46, 0x4f, 0x54, 0x5d, 0x62, 0x6b, 0x70, 0x79
};
/**
* crc7 - update the CRC7 for the data buffer
* @crc: previous CRC7 value
* @buffer: data pointer
* @len: number of bytes in the buffer
* Context: any
*
* Returns the updated CRC7 value.
*/
u8 crc7(u8 crc, const u8 *buffer, size_t len)
{
while (len--)
crc = crc7_byte(crc, *buffer++);
return crc;
}