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*/ 33struct 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 */ 54struct 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 61int 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 65int 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 72int 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 76int 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 81struct 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 */ 97static 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 103struct 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 */ 107void 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*/ 121static 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