forked from mirrors/linux
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
/*
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* Copyright (c) 2011 Broadcom Corporation
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*
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* Permission to use, copy, modify, and/or distribute this software for any
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* purpose with or without fee is hereby granted, provided that the above
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* copyright notice and this permission notice appear in all copies.
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*
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* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
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* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
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* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
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* SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
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* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
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* OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
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* CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
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*/
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#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
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#include <linux/module.h>
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#include <linux/crc8.h>
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#include <linux/printk.h>
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/**
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* crc8_populate_msb - fill crc table for given polynomial in reverse bit order.
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*
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* @table: table to be filled.
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* @polynomial: polynomial for which table is to be filled.
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*/
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void crc8_populate_msb(u8 table[CRC8_TABLE_SIZE], u8 polynomial)
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{
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int i, j;
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const u8 msbit = 0x80;
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u8 t = msbit;
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table[0] = 0;
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for (i = 1; i < CRC8_TABLE_SIZE; i *= 2) {
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t = (t << 1) ^ (t & msbit ? polynomial : 0);
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for (j = 0; j < i; j++)
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table[i+j] = table[j] ^ t;
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}
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}
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EXPORT_SYMBOL(crc8_populate_msb);
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/**
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* crc8_populate_lsb - fill crc table for given polynomial in regular bit order.
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*
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* @table: table to be filled.
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* @polynomial: polynomial for which table is to be filled.
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*/
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void crc8_populate_lsb(u8 table[CRC8_TABLE_SIZE], u8 polynomial)
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{
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int i, j;
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u8 t = 1;
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table[0] = 0;
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for (i = (CRC8_TABLE_SIZE >> 1); i; i >>= 1) {
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t = (t >> 1) ^ (t & 1 ? polynomial : 0);
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for (j = 0; j < CRC8_TABLE_SIZE; j += 2*i)
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table[i+j] = table[j] ^ t;
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}
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}
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EXPORT_SYMBOL(crc8_populate_lsb);
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/**
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* crc8 - calculate a crc8 over the given input data.
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*
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* @table: crc table used for calculation.
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* @pdata: pointer to data buffer.
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* @nbytes: number of bytes in data buffer.
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* @crc: previous returned crc8 value.
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*/
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u8 crc8(const u8 table[CRC8_TABLE_SIZE], const u8 *pdata, size_t nbytes, u8 crc)
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{
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/* loop over the buffer data */
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while (nbytes-- > 0)
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crc = table[(crc ^ *pdata++) & 0xff];
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return crc;
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}
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EXPORT_SYMBOL(crc8);
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MODULE_DESCRIPTION("CRC8 (by Williams, Ross N.) function");
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MODULE_AUTHOR("Broadcom Corporation");
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MODULE_LICENSE("Dual BSD/GPL");
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