mirror of
https://github.com/torvalds/linux
synced 2024-11-05 18:23:50 +00:00
e18baa7cc3
crc8() does not change the data passed to it, so the pointer argument should be declared const. This avoids callers that receive const data having to cast it to a non-const pointer to call crc8(). Link: https://lkml.kernel.org/r/20210329122409.3291-1-rf@opensource.cirrus.com Signed-off-by: Richard Fitzgerald <rf@opensource.cirrus.com> Acked-by: Randy Dunlap <rdunlap@infradead.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
86 lines
2.4 KiB
C
86 lines
2.4 KiB
C
/*
|
|
* Copyright (c) 2011 Broadcom Corporation
|
|
*
|
|
* Permission to use, copy, modify, and/or distribute this software for any
|
|
* purpose with or without fee is hereby granted, provided that the above
|
|
* copyright notice and this permission notice appear in all copies.
|
|
*
|
|
* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
|
|
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
|
|
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
|
|
* SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
|
|
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
|
|
* OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
|
|
* CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
|
|
*/
|
|
|
|
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
|
|
|
|
#include <linux/module.h>
|
|
#include <linux/crc8.h>
|
|
#include <linux/printk.h>
|
|
|
|
/**
|
|
* crc8_populate_msb - fill crc table for given polynomial in reverse bit order.
|
|
*
|
|
* @table: table to be filled.
|
|
* @polynomial: polynomial for which table is to be filled.
|
|
*/
|
|
void crc8_populate_msb(u8 table[CRC8_TABLE_SIZE], u8 polynomial)
|
|
{
|
|
int i, j;
|
|
const u8 msbit = 0x80;
|
|
u8 t = msbit;
|
|
|
|
table[0] = 0;
|
|
|
|
for (i = 1; i < CRC8_TABLE_SIZE; i *= 2) {
|
|
t = (t << 1) ^ (t & msbit ? polynomial : 0);
|
|
for (j = 0; j < i; j++)
|
|
table[i+j] = table[j] ^ t;
|
|
}
|
|
}
|
|
EXPORT_SYMBOL(crc8_populate_msb);
|
|
|
|
/**
|
|
* crc8_populate_lsb - fill crc table for given polynomial in regular bit order.
|
|
*
|
|
* @table: table to be filled.
|
|
* @polynomial: polynomial for which table is to be filled.
|
|
*/
|
|
void crc8_populate_lsb(u8 table[CRC8_TABLE_SIZE], u8 polynomial)
|
|
{
|
|
int i, j;
|
|
u8 t = 1;
|
|
|
|
table[0] = 0;
|
|
|
|
for (i = (CRC8_TABLE_SIZE >> 1); i; i >>= 1) {
|
|
t = (t >> 1) ^ (t & 1 ? polynomial : 0);
|
|
for (j = 0; j < CRC8_TABLE_SIZE; j += 2*i)
|
|
table[i+j] = table[j] ^ t;
|
|
}
|
|
}
|
|
EXPORT_SYMBOL(crc8_populate_lsb);
|
|
|
|
/**
|
|
* crc8 - calculate a crc8 over the given input data.
|
|
*
|
|
* @table: crc table used for calculation.
|
|
* @pdata: pointer to data buffer.
|
|
* @nbytes: number of bytes in data buffer.
|
|
* @crc: previous returned crc8 value.
|
|
*/
|
|
u8 crc8(const u8 table[CRC8_TABLE_SIZE], const u8 *pdata, size_t nbytes, u8 crc)
|
|
{
|
|
/* loop over the buffer data */
|
|
while (nbytes-- > 0)
|
|
crc = table[(crc ^ *pdata++) & 0xff];
|
|
|
|
return crc;
|
|
}
|
|
EXPORT_SYMBOL(crc8);
|
|
|
|
MODULE_DESCRIPTION("CRC8 (by Williams, Ross N.) function");
|
|
MODULE_AUTHOR("Broadcom Corporation");
|
|
MODULE_LICENSE("Dual BSD/GPL");
|