1*4882a593Smuzhiyun // SPDX-License-Identifier: GPL-2.0 2*4882a593Smuzhiyun /* 3*4882a593Smuzhiyun * Generic Reed Solomon encoder / decoder library 4*4882a593Smuzhiyun * 5*4882a593Smuzhiyun * Copyright 2002, Phil Karn, KA9Q 6*4882a593Smuzhiyun * May be used under the terms of the GNU General Public License (GPL) 7*4882a593Smuzhiyun * 8*4882a593Smuzhiyun * Adaption to the kernel by Thomas Gleixner (tglx@linutronix.de) 9*4882a593Smuzhiyun * 10*4882a593Smuzhiyun * Generic data width independent code which is included by the wrappers. 11*4882a593Smuzhiyun */ 12*4882a593Smuzhiyun { 13*4882a593Smuzhiyun struct rs_codec *rs = rsc->codec; 14*4882a593Smuzhiyun int i, j, pad; 15*4882a593Smuzhiyun int nn = rs->nn; 16*4882a593Smuzhiyun int nroots = rs->nroots; 17*4882a593Smuzhiyun uint16_t *alpha_to = rs->alpha_to; 18*4882a593Smuzhiyun uint16_t *index_of = rs->index_of; 19*4882a593Smuzhiyun uint16_t *genpoly = rs->genpoly; 20*4882a593Smuzhiyun uint16_t fb; 21*4882a593Smuzhiyun uint16_t msk = (uint16_t) rs->nn; 22*4882a593Smuzhiyun 23*4882a593Smuzhiyun /* Check length parameter for validity */ 24*4882a593Smuzhiyun pad = nn - nroots - len; 25*4882a593Smuzhiyun if (pad < 0 || pad >= nn) 26*4882a593Smuzhiyun return -ERANGE; 27*4882a593Smuzhiyun 28*4882a593Smuzhiyun for (i = 0; i < len; i++) { 29*4882a593Smuzhiyun fb = index_of[((((uint16_t) data[i])^invmsk) & msk) ^ par[0]]; 30*4882a593Smuzhiyun /* feedback term is non-zero */ 31*4882a593Smuzhiyun if (fb != nn) { 32*4882a593Smuzhiyun for (j = 1; j < nroots; j++) { 33*4882a593Smuzhiyun par[j] ^= alpha_to[rs_modnn(rs, fb + 34*4882a593Smuzhiyun genpoly[nroots - j])]; 35*4882a593Smuzhiyun } 36*4882a593Smuzhiyun } 37*4882a593Smuzhiyun /* Shift */ 38*4882a593Smuzhiyun memmove(&par[0], &par[1], sizeof(uint16_t) * (nroots - 1)); 39*4882a593Smuzhiyun if (fb != nn) { 40*4882a593Smuzhiyun par[nroots - 1] = alpha_to[rs_modnn(rs, 41*4882a593Smuzhiyun fb + genpoly[0])]; 42*4882a593Smuzhiyun } else { 43*4882a593Smuzhiyun par[nroots - 1] = 0; 44*4882a593Smuzhiyun } 45*4882a593Smuzhiyun } 46*4882a593Smuzhiyun return 0; 47*4882a593Smuzhiyun } 48