Greg Kroah-Hartman
939565a79b
Link: https://lore.kernel.org/r/20260121181411.452263583@linuxfoundation.org Tested-by: Salvatore Bonaccorso <carnil@debian.org> Tested-by: Shuah Khan <skhan@linuxfoundation.org> Tested-by: Florian Fainelli <florian.fainelli@broadcom.com> Tested-by: Brett A C Sheffield <bacs@librecast.net> Tested-by: Shung-Hsi Yu <shung-hsi.yu@suse.com> Tested-by: Jon Hunter <jonathanh@nvidia.com> Tested-by: Ron Economos <re@w6rz.net> Tested-by: Francesco Dolcini <francesco.dolcini@toradex.com> Tested-by: Mark Brown <broonie@kernel.org> Tested-by: Brett Mastbergen <bmastbergen@ciq.com> Tested-by: Peter Schneider <pschneider1968@googlemail.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
45 lines
1003 B
C
45 lines
1003 B
C
// SPDX-License-Identifier: GPL-2.0-only
|
|
/*
|
|
* crc4.c - simple crc-4 calculations.
|
|
*/
|
|
|
|
#include <linux/crc4.h>
|
|
#include <linux/module.h>
|
|
|
|
static const uint8_t crc4_tab[] = {
|
|
0x0, 0x7, 0xe, 0x9, 0xb, 0xc, 0x5, 0x2,
|
|
0x1, 0x6, 0xf, 0x8, 0xa, 0xd, 0x4, 0x3,
|
|
};
|
|
|
|
/**
|
|
* crc4 - calculate the 4-bit crc of a value.
|
|
* @c: starting crc4
|
|
* @x: value to checksum
|
|
* @bits: number of bits in @x to checksum
|
|
*
|
|
* Returns the crc4 value of @x, using polynomial 0b10111.
|
|
*
|
|
* The @x value is treated as left-aligned, and bits above @bits are ignored
|
|
* in the crc calculations.
|
|
*/
|
|
uint8_t crc4(uint8_t c, uint64_t x, int bits)
|
|
{
|
|
int i;
|
|
|
|
/* mask off anything above the top bit */
|
|
x &= (1ull << bits) - 1;
|
|
|
|
/* Align to 4-bits */
|
|
bits = (bits + 3) & ~0x3;
|
|
|
|
/* Calculate crc4 over four-bit nibbles, starting at the MSbit */
|
|
for (i = bits - 4; i >= 0; i -= 4)
|
|
c = crc4_tab[c ^ ((x >> i) & 0xf)];
|
|
|
|
return c;
|
|
}
|
|
EXPORT_SYMBOL_GPL(crc4);
|
|
|
|
MODULE_DESCRIPTION("CRC4 calculations");
|
|
MODULE_LICENSE("GPL");
|