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