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