1// SPDX-License-Identifier: GPL-2.0
2/*
3 * Generic Reed Solomon encoder / decoder library
4 *
5 * Copyright 2002, Phil Karn, KA9Q
6 * May be used under the terms of the GNU General Public License (GPL)
7 *
8 * Adaption to the kernel by Thomas Gleixner (tglx@linutronix.de)
9 *
10 * Generic data width independent code which is included by the wrappers.
11 */
12{
13	struct rs_codec *rs = rsc->codec;
14	int i, j, pad;
15	int nn = rs->nn;
16	int nroots = rs->nroots;
17	uint16_t *alpha_to = rs->alpha_to;
18	uint16_t *index_of = rs->index_of;
19	uint16_t *genpoly = rs->genpoly;
20	uint16_t fb;
21	uint16_t msk = (uint16_t) rs->nn;
22
23	/* Check length parameter for validity */
24	pad = nn - nroots - len;
25	if (pad < 0 || pad >= nn)
26		return -ERANGE;
27
28	for (i = 0; i < len; i++) {
29		fb = index_of[((((uint16_t) data[i])^invmsk) & msk) ^ par[0]];
30		/* feedback term is non-zero */
31		if (fb != nn) {
32			for (j = 1; j < nroots; j++) {
33				par[j] ^= alpha_to[rs_modnn(rs, fb +
34							 genpoly[nroots - j])];
35			}
36		}
37		/* Shift */
38		memmove(&par[0], &par[1], sizeof(uint16_t) * (nroots - 1));
39		if (fb != nn) {
40			par[nroots - 1] = alpha_to[rs_modnn(rs,
41							    fb + genpoly[0])];
42		} else {
43			par[nroots - 1] = 0;
44		}
45	}
46	return 0;
47}
48