// SPDX-License-Identifier: GPL-2.0

  /*

   * Generic Reed Solomon encoder / decoder library

   *

   * Copyright 2002, Phil Karn, KA9Q
   * May be used under the terms of the GNU General Public License (GPL)
   *
   * Adaption to the kernel by Thomas Gleixner (tglx@linutronix.de)
   *

   * Generic data width independent code which is included by the wrappers.

   */
  {

  	struct rs_codec *rs = rsc->codec;

  	int i, j, pad;
  	int nn = rs->nn;
  	int nroots = rs->nroots;
  	uint16_t *alpha_to = rs->alpha_to;
  	uint16_t *index_of = rs->index_of;
  	uint16_t *genpoly = rs->genpoly;
  	uint16_t fb;
  	uint16_t msk = (uint16_t) rs->nn;
  
  	/* Check length parameter for validity */
  	pad = nn - nroots - len;
  	if (pad < 0 || pad >= nn)
  		return -ERANGE;
  
  	for (i = 0; i < len; i++) {
  		fb = index_of[((((uint16_t) data[i])^invmsk) & msk) ^ par[0]];
  		/* feedback term is non-zero */

  		if (fb != nn) {

  			for (j = 1; j < nroots; j++) {

  				par[j] ^= alpha_to[rs_modnn(rs, fb +

  							 genpoly[nroots - j])];
  			}
  		}
  		/* Shift */
  		memmove(&par[0], &par[1], sizeof(uint16_t) * (nroots - 1));
  		if (fb != nn) {

  			par[nroots - 1] = alpha_to[rs_modnn(rs,

  							    fb + genpoly[0])];
  		} else {
  			par[nroots - 1] = 0;
  		}
  	}
  	return 0;
  }