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/*
* 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");
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