[mirror_ubuntu-hirsute-kernel.git] / lib / crc8.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], 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");
Commit	Line	Data
7150962d AS	1	/*
	2	* Copyright (c) 2011 Broadcom Corporation
	3	*
	4	* Permission to use, copy, modify, and/or distribute this software for any
	5	* purpose with or without fee is hereby granted, provided that the above
	6	* copyright notice and this permission notice appear in all copies.
	7	*
	8	* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
	9	* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
	10	* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
	11	* SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
	12	* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
	13	* OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
	14	* CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
	15	*/
	16
	17	#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
	18
	19	#include <linux/module.h>
	20	#include <linux/crc8.h>
	21	#include <linux/printk.h>
	22
	23	/*
	24	* crc8_populate_msb - fill crc table for given polynomial in reverse bit order.
	25	*
	26	* table: table to be filled.
	27	* polynomial: polynomial for which table is to be filled.
	28	*/
	29	void crc8_populate_msb(u8 table[CRC8_TABLE_SIZE], u8 polynomial)
	30	{
	31	int i, j;
	32	const u8 msbit = 0x80;
	33	u8 t = msbit;
	34
	35	table[0] = 0;
	36
	37	for (i = 1; i < CRC8_TABLE_SIZE; i *= 2) {
	38	t = (t << 1) ^ (t & msbit ? polynomial : 0);
	39	for (j = 0; j < i; j++)
	40	table[i+j] = table[j] ^ t;
	41	}
	42	}
	43	EXPORT_SYMBOL(crc8_populate_msb);
	44
	45	/*
	46	* crc8_populate_lsb - fill crc table for given polynomial in regular bit order.
	47	*
	48	* table: table to be filled.
	49	* polynomial: polynomial for which table is to be filled.
	50	*/
	51	void crc8_populate_lsb(u8 table[CRC8_TABLE_SIZE], u8 polynomial)
	52	{
	53	int i, j;
	54	u8 t = 1;
	55
	56	table[0] = 0;
	57
	58	for (i = (CRC8_TABLE_SIZE >> 1); i; i >>= 1) {
	59	t = (t >> 1) ^ (t & 1 ? polynomial : 0);
	60	for (j = 0; j < CRC8_TABLE_SIZE; j += 2*i)
	61	table[i+j] = table[j] ^ t;
	62	}
	63	}
	64	EXPORT_SYMBOL(crc8_populate_lsb);
65
66	/*
67	* crc8 - calculate a crc8 over the given input data.
68	*
69	* table: crc table used for calculation.
70	* pdata: pointer to data buffer.
71	* nbytes: number of bytes in data buffer.
72	* crc: previous returned crc8 value.
73	*/
74	u8 crc8(const u8 table[CRC8_TABLE_SIZE], u8 *pdata, size_t nbytes, u8 crc)
75	{
76	/* loop over the buffer data */
77	while (nbytes-- > 0)
78	crc = table[(crc ^ *pdata++) & 0xff];
79
80	return crc;
81	}
82	EXPORT_SYMBOL(crc8);
83
84	MODULE_DESCRIPTION("CRC8 (by Williams, Ross N.) function");
85	MODULE_AUTHOR("Broadcom Corporation");
86	MODULE_LICENSE("Dual BSD/GPL");