/*

   * include/linux/rslib.h
   *
   * Overview:
   *   Generic Reed Solomon encoder / decoder library

   *

   * Copyright (C) 2004 Thomas Gleixner (tglx@linutronix.de)
   *
   * RS code lifted from reed solomon library written by Phil Karn
   * Copyright 2002 Phil Karn, KA9Q
   *

   * $Id: rslib.h,v 1.4 2005/11/07 11:14:52 gleixner Exp $

   *
   * This program is free software; you can redistribute it and/or modify
   * it under the terms of the GNU General Public License version 2 as
   * published by the Free Software Foundation.
   */
  
  #ifndef _RSLIB_H_
  #define _RSLIB_H_
  
  #include <linux/list.h>

  /**

   * struct rs_control - rs control structure

   *

   * @mm:		Bits per symbol
   * @nn:		Symbols per block (= (1<<mm)-1)
   * @alpha_to:	log lookup table
   * @index_of:	Antilog lookup table

   * @genpoly:	Generator polynomial

   * @nroots:	Number of generator roots = number of parity symbols
   * @fcr:	First consecutive root, index form

   * @prim:	Primitive element, index form
   * @iprim:	prim-th root of 1, index form
   * @gfpoly:	The primitive generator polynominal

   * @gffunc:	Function to generate the field, if non-canonical representation

   * @users:	Users of this structure

   * @list:	List entry for the rs control list
  */
  struct rs_control {
  	int 		mm;
  	int 		nn;
  	uint16_t	*alpha_to;
  	uint16_t	*index_of;
  	uint16_t	*genpoly;
  	int 		nroots;
  	int 		fcr;
  	int 		prim;
  	int 		iprim;
  	int		gfpoly;

  	int		(*gffunc)(int);

  	int		users;
  	struct list_head list;
  };
  
  /* General purpose RS codec, 8-bit data width, symbol width 1-15 bit  */
  #ifdef CONFIG_REED_SOLOMON_ENC8
  int encode_rs8(struct rs_control *rs, uint8_t *data, int len, uint16_t *par,
  	       uint16_t invmsk);
  #endif
  #ifdef CONFIG_REED_SOLOMON_DEC8

  int decode_rs8(struct rs_control *rs, uint8_t *data, uint16_t *par, int len,

  		uint16_t *s, int no_eras, int *eras_pos, uint16_t invmsk,
  	       uint16_t *corr);
  #endif
  
  /* General purpose RS codec, 16-bit data width, symbol width 1-15 bit  */
  #ifdef CONFIG_REED_SOLOMON_ENC16
  int encode_rs16(struct rs_control *rs, uint16_t *data, int len, uint16_t *par,
  		uint16_t invmsk);
  #endif
  #ifdef CONFIG_REED_SOLOMON_DEC16
  int decode_rs16(struct rs_control *rs, uint16_t *data, uint16_t *par, int len,
  		uint16_t *s, int no_eras, int *eras_pos, uint16_t invmsk,
  		uint16_t *corr);
  #endif
  
  /* Create or get a matching rs control structure */

  struct rs_control *init_rs(int symsize, int gfpoly, int fcr, int prim,

  			   int nroots);

  struct rs_control *init_rs_non_canonical(int symsize, int (*func)(int),
                                           int fcr, int prim, int nroots);

  
  /* Release a rs control structure */
  void free_rs(struct rs_control *rs);
  
  /** modulo replacement for galois field arithmetics
   *
   *  @rs:	the rs control structure
   *  @x:		the value to reduce
   *
   *  where

   *  rs->mm = number of bits per symbol

   *  rs->nn = (2^rs->mm) - 1

   *

   *  Simple arithmetic modulo would return a wrong result for values
   *  >= 3 * rs->nn
  */
  static inline int rs_modnn(struct rs_control *rs, int x)
  {
  	while (x >= rs->nn) {
  		x -= rs->nn;
  		x = (x >> rs->mm) + (x & rs->nn);
  	}
  	return x;
  }
  
  #endif