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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 */
41 struct 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
59 int 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
63 int 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
70 int 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
74 int 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 */
80 struct rs_control *init_rs(int symsize, int gfpoly, int fcr, int prim,
81 			   int nroots);
82 struct 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 */
86 void 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 */
rs_modnn(struct rs_control * rs,int x)100 static 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