bch.h

 1/* SPDX-License-Identifier: GPL-2.0-only */
 2/*
 3 * Generic binary BCH encoding/decoding library
 4 *
 5 * Copyright © 2011 Parrot S.A.
 6 *
 7 * Author: Ivan Djelic <ivan.djelic@parrot.com>
 8 *
 9 * Description:
10 *
11 * This library provides runtime configurable encoding/decoding of binary
12 * Bose-Chaudhuri-Hocquenghem (BCH) codes.
13*/
14#ifndef _BCH_H
15#define _BCH_H
16
17#include <linux/types.h>
18
19/**
20 * struct bch_control - BCH control structure
21 * @m:          Galois field order
22 * @n:          maximum codeword size in bits (= 2^m-1)
23 * @t:          error correction capability in bits
24 * @ecc_bits:   ecc exact size in bits, i.e. generator polynomial degree (<=m*t)
25 * @ecc_bytes:  ecc max size (m*t bits) in bytes
26 * @a_pow_tab:  Galois field GF(2^m) exponentiation lookup table
27 * @a_log_tab:  Galois field GF(2^m) log lookup table
28 * @mod8_tab:   remainder generator polynomial lookup tables
29 * @ecc_buf:    ecc parity words buffer
30 * @ecc_buf2:   ecc parity words buffer
31 * @xi_tab:     GF(2^m) base for solving degree 2 polynomial roots
32 * @syn:        syndrome buffer
33 * @cache:      log-based polynomial representation buffer
34 * @elp:        error locator polynomial
35 * @poly_2t:    temporary polynomials of degree 2t
36 * @swap_bits:  swap bits within data and syndrome bytes
37 */
38struct bch_control {
39	unsigned int    m;
40	unsigned int    n;
41	unsigned int    t;
42	unsigned int    ecc_bits;
43	unsigned int    ecc_bytes;
44/* private: */
45	uint16_t       *a_pow_tab;
46	uint16_t       *a_log_tab;
47	uint32_t       *mod8_tab;
48	uint32_t       *ecc_buf;
49	uint32_t       *ecc_buf2;
50	unsigned int   *xi_tab;
51	unsigned int   *syn;
52	int            *cache;
53	struct gf_poly *elp;
54	struct gf_poly *poly_2t[4];
55	bool		swap_bits;
56};
57
58struct bch_control *bch_init(int m, int t, unsigned int prim_poly,
59			     bool swap_bits);
60
61void bch_free(struct bch_control *bch);
62
63void bch_encode(struct bch_control *bch, const uint8_t *data,
64		unsigned int len, uint8_t *ecc);
65
66int bch_decode(struct bch_control *bch, const uint8_t *data, unsigned int len,
67	       const uint8_t *recv_ecc, const uint8_t *calc_ecc,
68	       const unsigned int *syn, unsigned int *errloc);
69
70#endif /* _BCH_H */