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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 | */ |
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 |
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