| Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1 | /* |
| 2 | * include/linux/rslib.h |
| 3 | * |
| 4 | * Overview: |
| 5 | * Generic Reed Solomon encoder / decoder library |
| 6 | * |
| 7 | * Copyright (C) 2004 Thomas Gleixner (tglx@linutronix.de) |
| 8 | * |
| 9 | * RS code lifted from reed solomon library written by Phil Karn |
| 10 | * Copyright 2002 Phil Karn, KA9Q |
| 11 | * |
| 12 | * $Id: rslib.h,v 1.3 2004/10/05 22:08:22 gleixner Exp $ |
| 13 | * |
| 14 | * This program is free software; you can redistribute it and/or modify |
| 15 | * it under the terms of the GNU General Public License version 2 as |
| 16 | * published by the Free Software Foundation. |
| 17 | */ |
| 18 | |
| 19 | #ifndef _RSLIB_H_ |
| 20 | #define _RSLIB_H_ |
| 21 | |
| 22 | #include <linux/list.h> |
| 23 | |
| 24 | /** |
| 25 | * struct rs_control - rs control structure |
| 26 | * |
| 27 | * @mm: Bits per symbol |
| 28 | * @nn: Symbols per block (= (1<<mm)-1) |
| 29 | * @alpha_to: log lookup table |
| 30 | * @index_of: Antilog lookup table |
| 31 | * @genpoly: Generator polynomial |
| 32 | * @nroots: Number of generator roots = number of parity symbols |
| 33 | * @fcr: First consecutive root, index form |
| 34 | * @prim: Primitive element, index form |
| 35 | * @iprim: prim-th root of 1, index form |
| 36 | * @gfpoly: The primitive generator polynominal |
| 37 | * @users: Users of this structure |
| 38 | * @list: List entry for the rs control list |
| 39 | */ |
| 40 | struct rs_control { |
| 41 | int mm; |
| 42 | int nn; |
| 43 | uint16_t *alpha_to; |
| 44 | uint16_t *index_of; |
| 45 | uint16_t *genpoly; |
| 46 | int nroots; |
| 47 | int fcr; |
| 48 | int prim; |
| 49 | int iprim; |
| 50 | int gfpoly; |
| 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(int symsize, int gfpoly, int fcr, int prim, |
| 79 | int nroots); |
| 80 | |
| 81 | /* Release a rs control structure */ |
| 82 | void free_rs(struct rs_control *rs); |
| 83 | |
| 84 | /** modulo replacement for galois field arithmetics |
| 85 | * |
| 86 | * @rs: the rs control structure |
| 87 | * @x: the value to reduce |
| 88 | * |
| 89 | * where |
| 90 | * rs->mm = number of bits per symbol |
| 91 | * rs->nn = (2^rs->mm) - 1 |
| 92 | * |
| 93 | * Simple arithmetic modulo would return a wrong result for values |
| 94 | * >= 3 * rs->nn |
| 95 | */ |
| 96 | static inline int rs_modnn(struct rs_control *rs, int x) |
| 97 | { |
| 98 | while (x >= rs->nn) { |
| 99 | x -= rs->nn; |
| 100 | x = (x >> rs->mm) + (x & rs->nn); |
| 101 | } |
| 102 | return x; |
| 103 | } |
| 104 | |
| 105 | #endif |