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/* SPDX-License-Identifier: GPL-2.0-only */
* Generic binary BCH encoding/decoding library
* Copyright © 2011 Parrot S.A.
* Author: Ivan Djelic <>
* Description:
* This library provides runtime configurable encoding/decoding of binary
* Bose-Chaudhuri-Hocquenghem (BCH) codes.
#ifndef _BCH_H
#define _BCH_H
#include <linux/types.h>
* struct bch_control - BCH control structure
* @m: Galois field order
* @n: maximum codeword size in bits (= 2^m-1)
* @t: error correction capability in bits
* @ecc_bits: ecc exact size in bits, i.e. generator polynomial degree (<=m*t)
* @ecc_bytes: ecc max size (m*t bits) in bytes
* @a_pow_tab: Galois field GF(2^m) exponentiation lookup table
* @a_log_tab: Galois field GF(2^m) log lookup table
* @mod8_tab: remainder generator polynomial lookup tables
* @ecc_buf: ecc parity words buffer
* @ecc_buf2: ecc parity words buffer
* @xi_tab: GF(2^m) base for solving degree 2 polynomial roots
* @syn: syndrome buffer
* @cache: log-based polynomial representation buffer
* @elp: error locator polynomial
* @poly_2t: temporary polynomials of degree 2t
* @swap_bits: swap bits within data and syndrome bytes
struct bch_control {
unsigned int m;
unsigned int n;
unsigned int t;
unsigned int ecc_bits;
unsigned int ecc_bytes;
/* private: */
uint16_t *a_pow_tab;
uint16_t *a_log_tab;
uint32_t *mod8_tab;
uint32_t *ecc_buf;
uint32_t *ecc_buf2;
unsigned int *xi_tab;
unsigned int *syn;
int *cache;
struct gf_poly *elp;
struct gf_poly *poly_2t[4];
bool swap_bits;
struct bch_control *bch_init(int m, int t, unsigned int prim_poly,
bool swap_bits);
void bch_free(struct bch_control *bch);
void bch_encode(struct bch_control *bch, const uint8_t *data,
unsigned int len, uint8_t *ecc);
int bch_decode(struct bch_control *bch, const uint8_t *data, unsigned int len,
const uint8_t *recv_ecc, const uint8_t *calc_ecc,
const unsigned int *syn, unsigned int *errloc);
#endif /* _BCH_H */