1/*
2 * include/linux/rslib.h
3 *
4 * Overview:
5 *   Generic Reed Solomon encoder / decoder library
6 *
7 * Copyright (C) 2004 Thomas Gleixner (tglx@linutronix.de)
8 *
9 * RS code lifted from reed solomon library written by Phil Karn
10 * Copyright 2002 Phil Karn, KA9Q
11 *
12 * $Id: rslib.h,v 1.4 2005/11/07 11:14:52 gleixner Exp $
13 *
14 * This program is free software; you can redistribute it and/or modify
15 * it under the terms of the GNU General Public License version 2 as
16 * published by the Free Software Foundation.
17 */
18
19#ifndef _RSLIB_H_
20#define _RSLIB_H_
21
22#include <linux/list.h>
23
24/**
25 * struct rs_control - rs control structure
26 *
27 * @mm:		Bits per symbol
28 * @nn:		Symbols per block (= (1<<mm)-1)
29 * @alpha_to:	log lookup table
30 * @index_of:	Antilog lookup table
31 * @genpoly:	Generator polynomial
32 * @nroots:	Number of generator roots = number of parity symbols
33 * @fcr:	First consecutive root, index form
34 * @prim:	Primitive element, index form
35 * @iprim:	prim-th root of 1, index form
36 * @gfpoly:	The primitive generator polynominal
37 * @gffunc:	Function to generate the field, if non-canonical representation
38 * @users:	Users of this structure
39 * @list:	List entry for the rs control list
40*/
41struct rs_control {
42	int 		mm;
43	int 		nn;
44	uint16_t	*alpha_to;
45	uint16_t	*index_of;
46	uint16_t	*genpoly;
47	int 		nroots;
48	int 		fcr;
49	int 		prim;
50	int 		iprim;
51	int		gfpoly;
52	int		(*gffunc)(int);
53	int		users;
54	struct list_head list;
55};
56
57/* General purpose RS codec, 8-bit data width, symbol width 1-15 bit  */
58#ifdef CONFIG_REED_SOLOMON_ENC8
59int encode_rs8(struct rs_control *rs, uint8_t *data, int len, uint16_t *par,
60	       uint16_t invmsk);
61#endif
62#ifdef CONFIG_REED_SOLOMON_DEC8
63int decode_rs8(struct rs_control *rs, uint8_t *data, uint16_t *par, int len,
64		uint16_t *s, int no_eras, int *eras_pos, uint16_t invmsk,
65	       uint16_t *corr);
66#endif
67
68/* General purpose RS codec, 16-bit data width, symbol width 1-15 bit  */
69#ifdef CONFIG_REED_SOLOMON_ENC16
70int encode_rs16(struct rs_control *rs, uint16_t *data, int len, uint16_t *par,
71		uint16_t invmsk);
72#endif
73#ifdef CONFIG_REED_SOLOMON_DEC16
74int decode_rs16(struct rs_control *rs, uint16_t *data, uint16_t *par, int len,
75		uint16_t *s, int no_eras, int *eras_pos, uint16_t invmsk,
76		uint16_t *corr);
77#endif
78
79/* Create or get a matching rs control structure */
80struct rs_control *init_rs(int symsize, int gfpoly, int fcr, int prim,
81			   int nroots);
82struct rs_control *init_rs_non_canonical(int symsize, int (*func)(int),
83                                         int fcr, int prim, int nroots);
84
85/* Release a rs control structure */
86void free_rs(struct rs_control *rs);
87
88/** modulo replacement for galois field arithmetics
89 *
90 *  @rs:	the rs control structure
91 *  @x:		the value to reduce
92 *
93 *  where
94 *  rs->mm = number of bits per symbol
95 *  rs->nn = (2^rs->mm) - 1
96 *
97 *  Simple arithmetic modulo would return a wrong result for values
98 *  >= 3 * rs->nn
99*/
100static inline int rs_modnn(struct rs_control *rs, int x)
101{
102	while (x >= rs->nn) {
103		x -= rs->nn;
104		x = (x >> rs->mm) + (x & rs->nn);
105	}
106	return x;
107}
108
109#endif
110