1 | // SPDX-License-Identifier: GPL-2.0 |
2 | /* |
3 | * Generic Reed Solomon encoder / decoder library |
4 | * |
5 | * Copyright (C) 2004 Thomas Gleixner (tglx@linutronix.de) |
6 | * |
7 | * RS code lifted from reed solomon library written by Phil Karn |
8 | * Copyright 2002 Phil Karn, KA9Q |
9 | */ |
10 | #ifndef _RSLIB_H_ |
11 | #define _RSLIB_H_ |
12 | |
13 | #include <linux/types.h> /* for gfp_t */ |
14 | #include <linux/gfp.h> /* for GFP_KERNEL */ |
15 | |
16 | /** |
17 | * struct rs_codec - rs codec data |
18 | * |
19 | * @mm: Bits per symbol |
20 | * @nn: Symbols per block (= (1<<mm)-1) |
21 | * @alpha_to: log lookup table |
22 | * @index_of: Antilog lookup table |
23 | * @genpoly: Generator polynomial |
24 | * @nroots: Number of generator roots = number of parity symbols |
25 | * @fcr: First consecutive root, index form |
26 | * @prim: Primitive element, index form |
27 | * @iprim: prim-th root of 1, index form |
28 | * @gfpoly: The primitive generator polynominal |
29 | * @gffunc: Function to generate the field, if non-canonical representation |
30 | * @users: Users of this structure |
31 | * @list: List entry for the rs codec list |
32 | */ |
33 | struct rs_codec { |
34 | int mm; |
35 | int nn; |
36 | uint16_t *alpha_to; |
37 | uint16_t *index_of; |
38 | uint16_t *genpoly; |
39 | int nroots; |
40 | int fcr; |
41 | int prim; |
42 | int iprim; |
43 | int gfpoly; |
44 | int (*gffunc)(int); |
45 | int users; |
46 | struct list_head list; |
47 | }; |
48 | |
49 | /** |
50 | * struct rs_control - rs control structure per instance |
51 | * @codec: The codec used for this instance |
52 | * @buffers: Internal scratch buffers used in calls to decode_rs() |
53 | */ |
54 | struct rs_control { |
55 | struct rs_codec *codec; |
56 | uint16_t buffers[]; |
57 | }; |
58 | |
59 | /* General purpose RS codec, 8-bit data width, symbol width 1-15 bit */ |
60 | #ifdef CONFIG_REED_SOLOMON_ENC8 |
61 | int encode_rs8(struct rs_control *rs, uint8_t *data, int len, uint16_t *par, |
62 | uint16_t invmsk); |
63 | #endif |
64 | #ifdef CONFIG_REED_SOLOMON_DEC8 |
65 | int decode_rs8(struct rs_control *rs, uint8_t *data, uint16_t *par, int len, |
66 | uint16_t *s, int no_eras, int *eras_pos, uint16_t invmsk, |
67 | uint16_t *corr); |
68 | #endif |
69 | |
70 | /* General purpose RS codec, 16-bit data width, symbol width 1-15 bit */ |
71 | #ifdef CONFIG_REED_SOLOMON_ENC16 |
72 | int encode_rs16(struct rs_control *rs, uint16_t *data, int len, uint16_t *par, |
73 | uint16_t invmsk); |
74 | #endif |
75 | #ifdef CONFIG_REED_SOLOMON_DEC16 |
76 | int decode_rs16(struct rs_control *rs, uint16_t *data, uint16_t *par, int len, |
77 | uint16_t *s, int no_eras, int *eras_pos, uint16_t invmsk, |
78 | uint16_t *corr); |
79 | #endif |
80 | |
81 | struct rs_control *init_rs_gfp(int symsize, int gfpoly, int fcr, int prim, |
82 | int nroots, gfp_t gfp); |
83 | |
84 | /** |
85 | * init_rs - Create a RS control struct and initialize it |
86 | * @symsize: the symbol size (number of bits) |
87 | * @gfpoly: the extended Galois field generator polynomial coefficients, |
88 | * with the 0th coefficient in the low order bit. The polynomial |
89 | * must be primitive; |
90 | * @fcr: the first consecutive root of the rs code generator polynomial |
91 | * in index form |
92 | * @prim: primitive element to generate polynomial roots |
93 | * @nroots: RS code generator polynomial degree (number of roots) |
94 | * |
95 | * Allocations use GFP_KERNEL. |
96 | */ |
97 | static inline struct rs_control *init_rs(int symsize, int gfpoly, int fcr, |
98 | int prim, int nroots) |
99 | { |
100 | return init_rs_gfp(symsize, gfpoly, fcr, prim, nroots, GFP_KERNEL); |
101 | } |
102 | |
103 | struct rs_control *init_rs_non_canonical(int symsize, int (*func)(int), |
104 | int fcr, int prim, int nroots); |
105 | |
106 | /* Release a rs control structure */ |
107 | void free_rs(struct rs_control *rs); |
108 | |
109 | /** modulo replacement for galois field arithmetics |
110 | * |
111 | * @rs: Pointer to the RS codec |
112 | * @x: the value to reduce |
113 | * |
114 | * where |
115 | * rs->mm = number of bits per symbol |
116 | * rs->nn = (2^rs->mm) - 1 |
117 | * |
118 | * Simple arithmetic modulo would return a wrong result for values |
119 | * >= 3 * rs->nn |
120 | */ |
121 | static inline int rs_modnn(struct rs_codec *rs, int x) |
122 | { |
123 | while (x >= rs->nn) { |
124 | x -= rs->nn; |
125 | x = (x >> rs->mm) + (x & rs->nn); |
126 | } |
127 | return x; |
128 | } |
129 | |
130 | #endif |
131 | |