Revision 1d61754caa8c69f566504e63c8b3f3a2df0954c8 authored by Linus Torvalds on 21 October 2022, 21:43:09 UTC, committed by Linus Torvalds on 21 October 2022, 21:43:09 UTC
Pull xen fixes from Juergen Gross: "Just two fixes for the new 'virtio with grants' feature" * tag 'for-linus-6.1-rc2-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/xen/tip: xen/virtio: Convert PAGE_SIZE/PAGE_SHIFT/PFN_UP to Xen counterparts xen/virtio: Handle cases when page offset > PAGE_SIZE properly
crc4.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");
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