linux/include/linux/rslib.h
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   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 1.4 2005/11/07 11:14:52 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 * @gffunc:     Function to generate the field, if non-canonical representation
  38 * @users:      Users of this structure
  39 * @list:       List entry for the rs control list
  40*/
  41struct rs_control {
  42        int             mm;
  43        int             nn;
  44        uint16_t        *alpha_to;
  45        uint16_t        *index_of;
  46        uint16_t        *genpoly;
  47        int             nroots;
  48        int             fcr;
  49        int             prim;
  50        int             iprim;
  51        int             gfpoly;
  52        int             (*gffunc)(int);
  53        int             users;
  54        struct list_head list;
  55};
  56
  57/* General purpose RS codec, 8-bit data width, symbol width 1-15 bit  */
  58#ifdef CONFIG_REED_SOLOMON_ENC8
  59int encode_rs8(struct rs_control *rs, uint8_t *data, int len, uint16_t *par,
  60               uint16_t invmsk);
  61#endif
  62#ifdef CONFIG_REED_SOLOMON_DEC8
  63int decode_rs8(struct rs_control *rs, uint8_t *data, uint16_t *par, int len,
  64                uint16_t *s, int no_eras, int *eras_pos, uint16_t invmsk,
  65               uint16_t *corr);
  66#endif
  67
  68/* General purpose RS codec, 16-bit data width, symbol width 1-15 bit  */
  69#ifdef CONFIG_REED_SOLOMON_ENC16
  70int encode_rs16(struct rs_control *rs, uint16_t *data, int len, uint16_t *par,
  71                uint16_t invmsk);
  72#endif
  73#ifdef CONFIG_REED_SOLOMON_DEC16
  74int decode_rs16(struct rs_control *rs, uint16_t *data, uint16_t *par, int len,
  75                uint16_t *s, int no_eras, int *eras_pos, uint16_t invmsk,
  76                uint16_t *corr);
  77#endif
  78
  79/* Create or get a matching rs control structure */
  80struct rs_control *init_rs(int symsize, int gfpoly, int fcr, int prim,
  81                           int nroots);
  82struct rs_control *init_rs_non_canonical(int symsize, int (*func)(int),
  83                                         int fcr, int prim, int nroots);
  84
  85/* Release a rs control structure */
  86void free_rs(struct rs_control *rs);
  87
  88/** modulo replacement for galois field arithmetics
  89 *
  90 *  @rs:        the rs control structure
  91 *  @x:         the value to reduce
  92 *
  93 *  where
  94 *  rs->mm = number of bits per symbol
  95 *  rs->nn = (2^rs->mm) - 1
  96 *
  97 *  Simple arithmetic modulo would return a wrong result for values
  98 *  >= 3 * rs->nn
  99*/
 100static inline int rs_modnn(struct rs_control *rs, int x)
 101{
 102        while (x >= rs->nn) {
 103                x -= rs->nn;
 104                x = (x >> rs->mm) + (x & rs->nn);
 105        }
 106        return x;
 107}
 108
 109#endif
 110
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