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
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