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