Orange Pi5 kernel

^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  1) // SPDX-License-Identifier: GPL-2.0-only
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  2) /*
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  3)  * crc4.c - simple crc-4 calculations.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  4)  */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  5) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  6) #include <linux/crc4.h>
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  7) #include <linux/module.h>
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  8) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  9) static const uint8_t crc4_tab[] = {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 10) 	0x0, 0x7, 0xe, 0x9, 0xb, 0xc, 0x5, 0x2,
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 11) 	0x1, 0x6, 0xf, 0x8, 0xa, 0xd, 0x4, 0x3,
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 12) };
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 13) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 14) /**
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 15)  * crc4 - calculate the 4-bit crc of a value.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 16)  * @c:    starting crc4
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 17)  * @x:    value to checksum
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 18)  * @bits: number of bits in @x to checksum
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 19)  *
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 20)  * Returns the crc4 value of @x, using polynomial 0b10111.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 21)  *
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 22)  * The @x value is treated as left-aligned, and bits above @bits are ignored
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 23)  * in the crc calculations.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 24)  */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 25) uint8_t crc4(uint8_t c, uint64_t x, int bits)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 26) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 27) 	int i;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 28) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 29) 	/* mask off anything above the top bit */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 30) 	x &= (1ull << bits) - 1;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 31) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 32) 	/* Align to 4-bits */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 33) 	bits = (bits + 3) & ~0x3;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 34) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 35) 	/* Calculate crc4 over four-bit nibbles, starting at the MSbit */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 36) 	for (i = bits - 4; i >= 0; i -= 4)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 37) 		c = crc4_tab[c ^ ((x >> i) & 0xf)];
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 38) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 39) 	return c;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 40) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 41) EXPORT_SYMBOL_GPL(crc4);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 42) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 43) MODULE_DESCRIPTION("CRC4 calculations");
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 44) MODULE_LICENSE("GPL");