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1 /* |
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2 * include/linux/rslib.h |
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3 * |
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4 * Overview: |
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5 * Generic Reed Solomon encoder / decoder library |
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6 * |
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7 * Copyright (C) 2004 Thomas Gleixner (tglx@linutronix.de) |
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8 * |
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9 * RS code lifted from reed solomon library written by Phil Karn |
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10 * Copyright 2002 Phil Karn, KA9Q |
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11 * |
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12 * $Id: rslib.h,v 1.4 2005/11/07 11:14:52 gleixner Exp $ |
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13 * |
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14 * This program is free software; you can redistribute it and/or modify |
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15 * it under the terms of the GNU General Public License version 2 as |
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16 * published by the Free Software Foundation. |
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17 */ |
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18 |
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19 #ifndef _RSLIB_H_ |
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20 #define _RSLIB_H_ |
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21 |
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22 #include <linux/list.h> |
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23 |
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24 /** |
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25 * struct rs_control - rs control structure |
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26 * |
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27 * @mm: Bits per symbol |
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28 * @nn: Symbols per block (= (1<<mm)-1) |
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29 * @alpha_to: log lookup table |
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30 * @index_of: Antilog lookup table |
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31 * @genpoly: Generator polynomial |
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32 * @nroots: Number of generator roots = number of parity symbols |
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33 * @fcr: First consecutive root, index form |
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34 * @prim: Primitive element, index form |
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35 * @iprim: prim-th root of 1, index form |
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36 * @gfpoly: The primitive generator polynominal |
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37 * @gffunc: Function to generate the field, if non-canonical representation |
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38 * @users: Users of this structure |
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39 * @list: List entry for the rs control list |
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40 */ |
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41 struct rs_control { |
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42 int mm; |
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43 int nn; |
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44 uint16_t *alpha_to; |
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45 uint16_t *index_of; |
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46 uint16_t *genpoly; |
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47 int nroots; |
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48 int fcr; |
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49 int prim; |
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50 int iprim; |
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51 int gfpoly; |
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52 int (*gffunc)(int); |
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53 int users; |
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54 struct list_head list; |
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55 }; |
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56 |
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57 /* General purpose RS codec, 8-bit data width, symbol width 1-15 bit */ |
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58 #ifdef CONFIG_REED_SOLOMON_ENC8 |
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59 int encode_rs8(struct rs_control *rs, uint8_t *data, int len, uint16_t *par, |
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60 uint16_t invmsk); |
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61 #endif |
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62 #ifdef CONFIG_REED_SOLOMON_DEC8 |
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63 int decode_rs8(struct rs_control *rs, uint8_t *data, uint16_t *par, int len, |
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64 uint16_t *s, int no_eras, int *eras_pos, uint16_t invmsk, |
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65 uint16_t *corr); |
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66 #endif |
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67 |
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68 /* General purpose RS codec, 16-bit data width, symbol width 1-15 bit */ |
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69 #ifdef CONFIG_REED_SOLOMON_ENC16 |
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70 int encode_rs16(struct rs_control *rs, uint16_t *data, int len, uint16_t *par, |
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71 uint16_t invmsk); |
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72 #endif |
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73 #ifdef CONFIG_REED_SOLOMON_DEC16 |
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74 int decode_rs16(struct rs_control *rs, uint16_t *data, uint16_t *par, int len, |
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75 uint16_t *s, int no_eras, int *eras_pos, uint16_t invmsk, |
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76 uint16_t *corr); |
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77 #endif |
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78 |
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79 /* Create or get a matching rs control structure */ |
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80 struct rs_control *init_rs(int symsize, int gfpoly, int fcr, int prim, |
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81 int nroots); |
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82 struct rs_control *init_rs_non_canonical(int symsize, int (*func)(int), |
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83 int fcr, int prim, int nroots); |
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84 |
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85 /* Release a rs control structure */ |
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86 void free_rs(struct rs_control *rs); |
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87 |
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88 /** modulo replacement for galois field arithmetics |
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89 * |
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90 * @rs: the rs control structure |
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91 * @x: the value to reduce |
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92 * |
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93 * where |
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94 * rs->mm = number of bits per symbol |
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95 * rs->nn = (2^rs->mm) - 1 |
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96 * |
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97 * Simple arithmetic modulo would return a wrong result for values |
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98 * >= 3 * rs->nn |
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99 */ |
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100 static inline int rs_modnn(struct rs_control *rs, int x) |
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101 { |
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102 while (x >= rs->nn) { |
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103 x -= rs->nn; |
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104 x = (x >> rs->mm) + (x & rs->nn); |
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105 } |
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106 return x; |
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107 } |
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108 |
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109 #endif |