mirror of
https://github.com/torvalds/linux.git
synced 2024-11-16 17:12:06 +00:00
1836eea209
This eliminates a 1-bit left shift in every single caller, and makes the inner loop of the CRC computation more efficient. Renamed crc7 to crc7_be (big-endian) since the interface changed. Also purged #include <linux/crc7.h> from files that don't use it at all. Signed-off-by: George Spelvin <linux@horizon.com> Reviewed-by: Pavel Machek <pavel@ucw.cz> Acked-by: Ulf Hansson <ulf.hansson@linaro.org> Signed-off-by: John W. Linville <linville@tuxdriver.com>
77 lines
2.6 KiB
C
77 lines
2.6 KiB
C
/*
|
|
* 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/module.h>
|
|
#include <linux/crc7.h>
|
|
|
|
|
|
/*
|
|
* Table for CRC-7 (polynomial x^7 + x^3 + 1).
|
|
* This is a big-endian CRC (msbit is highest power of x),
|
|
* aligned so the msbit of the byte is the x^6 coefficient
|
|
* and the lsbit is not used.
|
|
*/
|
|
const u8 crc7_be_syndrome_table[256] = {
|
|
0x00, 0x12, 0x24, 0x36, 0x48, 0x5a, 0x6c, 0x7e,
|
|
0x90, 0x82, 0xb4, 0xa6, 0xd8, 0xca, 0xfc, 0xee,
|
|
0x32, 0x20, 0x16, 0x04, 0x7a, 0x68, 0x5e, 0x4c,
|
|
0xa2, 0xb0, 0x86, 0x94, 0xea, 0xf8, 0xce, 0xdc,
|
|
0x64, 0x76, 0x40, 0x52, 0x2c, 0x3e, 0x08, 0x1a,
|
|
0xf4, 0xe6, 0xd0, 0xc2, 0xbc, 0xae, 0x98, 0x8a,
|
|
0x56, 0x44, 0x72, 0x60, 0x1e, 0x0c, 0x3a, 0x28,
|
|
0xc6, 0xd4, 0xe2, 0xf0, 0x8e, 0x9c, 0xaa, 0xb8,
|
|
0xc8, 0xda, 0xec, 0xfe, 0x80, 0x92, 0xa4, 0xb6,
|
|
0x58, 0x4a, 0x7c, 0x6e, 0x10, 0x02, 0x34, 0x26,
|
|
0xfa, 0xe8, 0xde, 0xcc, 0xb2, 0xa0, 0x96, 0x84,
|
|
0x6a, 0x78, 0x4e, 0x5c, 0x22, 0x30, 0x06, 0x14,
|
|
0xac, 0xbe, 0x88, 0x9a, 0xe4, 0xf6, 0xc0, 0xd2,
|
|
0x3c, 0x2e, 0x18, 0x0a, 0x74, 0x66, 0x50, 0x42,
|
|
0x9e, 0x8c, 0xba, 0xa8, 0xd6, 0xc4, 0xf2, 0xe0,
|
|
0x0e, 0x1c, 0x2a, 0x38, 0x46, 0x54, 0x62, 0x70,
|
|
0x82, 0x90, 0xa6, 0xb4, 0xca, 0xd8, 0xee, 0xfc,
|
|
0x12, 0x00, 0x36, 0x24, 0x5a, 0x48, 0x7e, 0x6c,
|
|
0xb0, 0xa2, 0x94, 0x86, 0xf8, 0xea, 0xdc, 0xce,
|
|
0x20, 0x32, 0x04, 0x16, 0x68, 0x7a, 0x4c, 0x5e,
|
|
0xe6, 0xf4, 0xc2, 0xd0, 0xae, 0xbc, 0x8a, 0x98,
|
|
0x76, 0x64, 0x52, 0x40, 0x3e, 0x2c, 0x1a, 0x08,
|
|
0xd4, 0xc6, 0xf0, 0xe2, 0x9c, 0x8e, 0xb8, 0xaa,
|
|
0x44, 0x56, 0x60, 0x72, 0x0c, 0x1e, 0x28, 0x3a,
|
|
0x4a, 0x58, 0x6e, 0x7c, 0x02, 0x10, 0x26, 0x34,
|
|
0xda, 0xc8, 0xfe, 0xec, 0x92, 0x80, 0xb6, 0xa4,
|
|
0x78, 0x6a, 0x5c, 0x4e, 0x30, 0x22, 0x14, 0x06,
|
|
0xe8, 0xfa, 0xcc, 0xde, 0xa0, 0xb2, 0x84, 0x96,
|
|
0x2e, 0x3c, 0x0a, 0x18, 0x66, 0x74, 0x42, 0x50,
|
|
0xbe, 0xac, 0x9a, 0x88, 0xf6, 0xe4, 0xd2, 0xc0,
|
|
0x1c, 0x0e, 0x38, 0x2a, 0x54, 0x46, 0x70, 0x62,
|
|
0x8c, 0x9e, 0xa8, 0xba, 0xc4, 0xd6, 0xe0, 0xf2
|
|
};
|
|
EXPORT_SYMBOL(crc7_be_syndrome_table);
|
|
|
|
/**
|
|
* 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.
|
|
* The CRC7 is left-aligned in the byte (the lsbit is always 0), as that
|
|
* makes the computation easier, and all callers want it in that form.
|
|
*
|
|
*/
|
|
u8 crc7_be(u8 crc, const u8 *buffer, size_t len)
|
|
{
|
|
while (len--)
|
|
crc = crc7_be_byte(crc, *buffer++);
|
|
return crc;
|
|
}
|
|
EXPORT_SYMBOL(crc7_be);
|
|
|
|
MODULE_DESCRIPTION("CRC7 calculations");
|
|
MODULE_LICENSE("GPL");
|