include/linux/bch.h

0001 /* SPDX-License-Identifier: GPL-2.0-only */
0002 /*
0003  * Generic binary BCH encoding/decoding library
0004  *
0005  * Copyright © 2011 Parrot S.A.
0006  *
0007  * Author: Ivan Djelic <ivan.djelic@parrot.com>
0008  *
0009  * Description:
0010  *
0011  * This library provides runtime configurable encoding/decoding of binary
0012  * Bose-Chaudhuri-Hocquenghem (BCH) codes.
0013 */
0014 #ifndef _BCH_H
0015 #define _BCH_H
0016
0017 #include <linux/types.h>
0018
0019 /**
0020  * struct bch_control - BCH control structure
0021  * @m:          Galois field order
0022  * @n:          maximum codeword size in bits (= 2^m-1)
0023  * @t:          error correction capability in bits
0024  * @ecc_bits:   ecc exact size in bits, i.e. generator polynomial degree (<=m*t)
0025  * @ecc_bytes:  ecc max size (m*t bits) in bytes
0026  * @a_pow_tab:  Galois field GF(2^m) exponentiation lookup table
0027  * @a_log_tab:  Galois field GF(2^m) log lookup table
0028  * @mod8_tab:   remainder generator polynomial lookup tables
0029  * @ecc_buf:    ecc parity words buffer
0030  * @ecc_buf2:   ecc parity words buffer
0031  * @xi_tab:     GF(2^m) base for solving degree 2 polynomial roots
0032  * @syn:        syndrome buffer
0033  * @cache:      log-based polynomial representation buffer
0034  * @elp:        error locator polynomial
0035  * @poly_2t:    temporary polynomials of degree 2t
0036  * @swap_bits:  swap bits within data and syndrome bytes
0037  */
0038 struct bch_control {
0039     unsigned int    m;
0040     unsigned int    n;
0041     unsigned int    t;
0042     unsigned int    ecc_bits;
0043     unsigned int    ecc_bytes;
0044 /* private: */
0045     uint16_t       *a_pow_tab;
0046     uint16_t       *a_log_tab;
0047     uint32_t       *mod8_tab;
0048     uint32_t       *ecc_buf;
0049     uint32_t       *ecc_buf2;
0050     unsigned int   *xi_tab;
0051     unsigned int   *syn;
0052     int            *cache;
0053     struct gf_poly *elp;
0054     struct gf_poly *poly_2t[4];
0055     bool        swap_bits;
0056 };
0057
0058 struct bch_control *bch_init(int m, int t, unsigned int prim_poly,
0059                  bool swap_bits);
0060
0061 void bch_free(struct bch_control *bch);
0062
0063 void bch_encode(struct bch_control *bch, const uint8_t *data,
0064         unsigned int len, uint8_t *ecc);
0065
0066 int bch_decode(struct bch_control *bch, const uint8_t *data, unsigned int len,
0067            const uint8_t *recv_ecc, const uint8_t *calc_ecc,
0068            const unsigned int *syn, unsigned int *errloc);
0069
0070 #endif /* _BCH_H */