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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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