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/list.h> |

14 | #include <linux/types.h> /* for gfp_t */ |

15 | #include <linux/gfp.h> /* for GFP_KERNEL */ |

16 | |

17 | /** |

18 | * struct rs_codec - rs codec data |

19 | * |

20 | * @mm: Bits per symbol |

21 | * @nn: Symbols per block (= (1<<mm)-1) |

22 | * @alpha_to: log lookup table |

23 | * @index_of: Antilog lookup table |

24 | * @genpoly: Generator polynomial |

25 | * @nroots: Number of generator roots = number of parity symbols |

26 | * @fcr: First consecutive root, index form |

27 | * @prim: Primitive element, index form |

28 | * @iprim: prim-th root of 1, index form |

29 | * @gfpoly: The primitive generator polynominal |

30 | * @gffunc: Function to generate the field, if non-canonical representation |

31 | * @users: Users of this structure |

32 | * @list: List entry for the rs codec list |

33 | */ |

34 | struct rs_codec { |

35 | int mm; |

36 | int nn; |

37 | uint16_t *alpha_to; |

38 | uint16_t *index_of; |

39 | uint16_t *genpoly; |

40 | int nroots; |

41 | int fcr; |

42 | int prim; |

43 | int iprim; |

44 | int gfpoly; |

45 | int (*gffunc)(int); |

46 | int users; |

47 | struct list_head list; |

48 | }; |

49 | |

50 | /** |

51 | * struct rs_control - rs control structure per instance |

52 | * @codec: The codec used for this instance |

53 | * @buffers: Internal scratch buffers used in calls to decode_rs() |

54 | */ |

55 | struct rs_control { |

56 | struct rs_codec *codec; |

57 | uint16_t buffers[0]; |

58 | }; |

59 | |

60 | /* General purpose RS codec, 8-bit data width, symbol width 1-15 bit */ |

61 | #ifdef CONFIG_REED_SOLOMON_ENC8 |

62 | int encode_rs8(struct rs_control *rs, uint8_t *data, int len, uint16_t *par, |

63 | uint16_t invmsk); |

64 | #endif |

65 | #ifdef CONFIG_REED_SOLOMON_DEC8 |

66 | int decode_rs8(struct rs_control *rs, uint8_t *data, uint16_t *par, int len, |

67 | uint16_t *s, int no_eras, int *eras_pos, uint16_t invmsk, |

68 | uint16_t *corr); |

69 | #endif |

70 | |

71 | /* General purpose RS codec, 16-bit data width, symbol width 1-15 bit */ |

72 | #ifdef CONFIG_REED_SOLOMON_ENC16 |

73 | int encode_rs16(struct rs_control *rs, uint16_t *data, int len, uint16_t *par, |

74 | uint16_t invmsk); |

75 | #endif |

76 | #ifdef CONFIG_REED_SOLOMON_DEC16 |

77 | int decode_rs16(struct rs_control *rs, uint16_t *data, uint16_t *par, int len, |

78 | uint16_t *s, int no_eras, int *eras_pos, uint16_t invmsk, |

79 | uint16_t *corr); |

80 | #endif |

81 | |

82 | struct rs_control *init_rs_gfp(int symsize, int gfpoly, int fcr, int prim, |

83 | int nroots, gfp_t gfp); |

84 | |

85 | /** |

86 | * init_rs - Create a RS control struct and initialize it |

87 | * @symsize: the symbol size (number of bits) |

88 | * @gfpoly: the extended Galois field generator polynomial coefficients, |

89 | * with the 0th coefficient in the low order bit. The polynomial |

90 | * must be primitive; |

91 | * @fcr: the first consecutive root of the rs code generator polynomial |

92 | * in index form |

93 | * @prim: primitive element to generate polynomial roots |

94 | * @nroots: RS code generator polynomial degree (number of roots) |

95 | * |

96 | * Allocations use GFP_KERNEL. |

97 | */ |

98 | static inline struct rs_control *init_rs(int symsize, int gfpoly, int fcr, |

99 | int prim, int nroots) |

100 | { |

101 | return init_rs_gfp(symsize, gfpoly, fcr, prim, nroots, GFP_KERNEL); |

102 | } |

103 | |

104 | struct rs_control *init_rs_non_canonical(int symsize, int (*func)(int), |

105 | int fcr, int prim, int nroots); |

106 | |

107 | /* Release a rs control structure */ |

108 | void free_rs(struct rs_control *rs); |

109 | |

110 | /** modulo replacement for galois field arithmetics |

111 | * |

112 | * @rs: Pointer to the RS codec |

113 | * @x: the value to reduce |

114 | * |

115 | * where |

116 | * rs->mm = number of bits per symbol |

117 | * rs->nn = (2^rs->mm) - 1 |

118 | * |

119 | * Simple arithmetic modulo would return a wrong result for values |

120 | * >= 3 * rs->nn |

121 | */ |

122 | static inline int rs_modnn(struct rs_codec *rs, int x) |

123 | { |

124 | while (x >= rs->nn) { |

125 | x -= rs->nn; |

126 | x = (x >> rs->mm) + (x & rs->nn); |

127 | } |

128 | return x; |

129 | } |

130 | |

131 | #endif |

132 |