/* * crc4.c - simple crc-4 calculations. * * This source code is licensed under the GNU General Public License, Version * 2. See the file COPYING for more details. */ #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. * @crc:  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");