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/types.h>	/* for gfp_t */
14#include <linux/gfp.h>		/* for GFP_KERNEL */
15
16/**
17 * struct rs_codec - rs codec data
18 *
19 * @mm:		Bits per symbol
20 * @nn:		Symbols per block (= (1<<mm)-1)
21 * @alpha_to:	log lookup table
22 * @index_of:	Antilog lookup table
23 * @genpoly:	Generator polynomial
24 * @nroots:	Number of generator roots = number of parity symbols
25 * @fcr:	First consecutive root, index form
26 * @prim:	Primitive element, index form
27 * @iprim:	prim-th root of 1, index form
28 * @gfpoly:	The primitive generator polynominal
29 * @gffunc:	Function to generate the field, if non-canonical representation
30 * @users:	Users of this structure
31 * @list:	List entry for the rs codec list
32*/
33struct rs_codec {
34	int		mm;
35	int		nn;
36	uint16_t	*alpha_to;
37	uint16_t	*index_of;
38	uint16_t	*genpoly;
39	int		nroots;
40	int		fcr;
41	int		prim;
42	int		iprim;
43	int		gfpoly;
44	int		(*gffunc)(int);
45	int		users;
46	struct list_head list;
47};
48
49/**
50 * struct rs_control - rs control structure per instance
51 * @codec:	The codec used for this instance
52 * @buffers:	Internal scratch buffers used in calls to decode_rs()
53 */
54struct rs_control {
55	struct rs_codec	*codec;
56	uint16_t	buffers[];
57};
58
59/* General purpose RS codec, 8-bit data width, symbol width 1-15 bit  */
60#ifdef CONFIG_REED_SOLOMON_ENC8
61int encode_rs8(struct rs_control *rs, uint8_t *data, int len, uint16_t *par,
62	       uint16_t invmsk);
63#endif
64#ifdef CONFIG_REED_SOLOMON_DEC8
65int decode_rs8(struct rs_control *rs, uint8_t *data, uint16_t *par, int len,
66		uint16_t *s, int no_eras, int *eras_pos, uint16_t invmsk,
67	       uint16_t *corr);
68#endif
69
70/* General purpose RS codec, 16-bit data width, symbol width 1-15 bit  */
71#ifdef CONFIG_REED_SOLOMON_ENC16
72int encode_rs16(struct rs_control *rs, uint16_t *data, int len, uint16_t *par,
73		uint16_t invmsk);
74#endif
75#ifdef CONFIG_REED_SOLOMON_DEC16
76int decode_rs16(struct rs_control *rs, uint16_t *data, uint16_t *par, int len,
77		uint16_t *s, int no_eras, int *eras_pos, uint16_t invmsk,
78		uint16_t *corr);
79#endif
80
81struct rs_control *init_rs_gfp(int symsize, int gfpoly, int fcr, int prim,
82			       int nroots, gfp_t gfp);
83
84/**
85 * init_rs - Create a RS control struct and initialize it
86 *  @symsize:	the symbol size (number of bits)
87 *  @gfpoly:	the extended Galois field generator polynomial coefficients,
88 *		with the 0th coefficient in the low order bit. The polynomial
89 *		must be primitive;
90 *  @fcr:	the first consecutive root of the rs code generator polynomial
91 *		in index form
92 *  @prim:	primitive element to generate polynomial roots
93 *  @nroots:	RS code generator polynomial degree (number of roots)
94 *
95 * Allocations use GFP_KERNEL.
96 */
97static inline struct rs_control *init_rs(int symsize, int gfpoly, int fcr,
98					 int prim, int nroots)
99{
100	return init_rs_gfp(symsize, gfpoly, fcr, prim, nroots, GFP_KERNEL);
101}
102
103struct rs_control *init_rs_non_canonical(int symsize, int (*func)(int),
104					 int fcr, int prim, int nroots);
105
106/* Release a rs control structure */
107void free_rs(struct rs_control *rs);
108
109/** modulo replacement for galois field arithmetics
110 *
111 *  @rs:	Pointer to the RS codec
112 *  @x:		the value to reduce
113 *
114 *  where
115 *  rs->mm = number of bits per symbol
116 *  rs->nn = (2^rs->mm) - 1
117 *
118 *  Simple arithmetic modulo would return a wrong result for values
119 *  >= 3 * rs->nn
120*/
121static inline int rs_modnn(struct rs_codec *rs, int x)
122{
123	while (x >= rs->nn) {
124		x -= rs->nn;
125		x = (x >> rs->mm) + (x & rs->nn);
126	}
127	return x;
128}
129
130#endif
131