include/linux/rslib.h

   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  * @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