/* -*- linux-c -*- ------------------------------------------------------- *
   *
   *   Copyright 2002 H. Peter Anvin - All Rights Reserved
   *
   *   This program is free software; you can redistribute it and/or modify
   *   it under the terms of the GNU General Public License as published by
   *   the Free Software Foundation, Inc., 53 Temple Place Ste 330,

   *   Boston MA 02111-1307, USA; either version 2 of the License, or

   *   (at your option) any later version; incorporated herein by reference.
   *
   * ----------------------------------------------------------------------- */
  
  /*

   * raid6/recov.c

   *
   * RAID-6 data recovery in dual failure mode.  In single failure mode,
   * use the RAID-5 algorithm (or, in the case of Q failure, just reconstruct
   * the syndrome.)
   */

  #include <linux/export.h>

  #include <linux/raid/pq.h>

  
  /* Recover two failed data blocks. */
  void raid6_2data_recov(int disks, size_t bytes, int faila, int failb,
  		       void **ptrs)
  {
  	u8 *p, *q, *dp, *dq;
  	u8 px, qx, db;
  	const u8 *pbmul;	/* P multiplier table for B data */
  	const u8 *qmul;		/* Q multiplier table (for both) */
  
  	p = (u8 *)ptrs[disks-2];
  	q = (u8 *)ptrs[disks-1];
  
  	/* Compute syndrome with zero for the missing data pages
  	   Use the dead data pages as temporary storage for
  	   delta p and delta q */
  	dp = (u8 *)ptrs[faila];
  	ptrs[faila] = (void *)raid6_empty_zero_page;
  	ptrs[disks-2] = dp;
  	dq = (u8 *)ptrs[failb];
  	ptrs[failb] = (void *)raid6_empty_zero_page;
  	ptrs[disks-1] = dq;
  
  	raid6_call.gen_syndrome(disks, bytes, ptrs);
  
  	/* Restore pointer table */
  	ptrs[faila]   = dp;
  	ptrs[failb]   = dq;
  	ptrs[disks-2] = p;
  	ptrs[disks-1] = q;
  
  	/* Now, pick the proper data tables */
  	pbmul = raid6_gfmul[raid6_gfexi[failb-faila]];
  	qmul  = raid6_gfmul[raid6_gfinv[raid6_gfexp[faila]^raid6_gfexp[failb]]];
  
  	/* Now do it... */
  	while ( bytes-- ) {
  		px    = *p ^ *dp;
  		qx    = qmul[*q ^ *dq];
  		*dq++ = db = pbmul[px] ^ qx; /* Reconstructed B */
  		*dp++ = db ^ px; /* Reconstructed A */
  		p++; q++;
  	}
  }

  EXPORT_SYMBOL_GPL(raid6_2data_recov);

  
  /* Recover failure of one data block plus the P block */
  void raid6_datap_recov(int disks, size_t bytes, int faila, void **ptrs)
  {
  	u8 *p, *q, *dq;
  	const u8 *qmul;		/* Q multiplier table */
  
  	p = (u8 *)ptrs[disks-2];
  	q = (u8 *)ptrs[disks-1];
  
  	/* Compute syndrome with zero for the missing data page
  	   Use the dead data page as temporary storage for delta q */
  	dq = (u8 *)ptrs[faila];
  	ptrs[faila] = (void *)raid6_empty_zero_page;
  	ptrs[disks-1] = dq;
  
  	raid6_call.gen_syndrome(disks, bytes, ptrs);
  
  	/* Restore pointer table */
  	ptrs[faila]   = dq;
  	ptrs[disks-1] = q;
  
  	/* Now, pick the proper data tables */
  	qmul  = raid6_gfmul[raid6_gfinv[raid6_gfexp[faila]]];
  
  	/* Now do it... */
  	while ( bytes-- ) {
  		*p++ ^= *dq = qmul[*q ^ *dq];
  		q++; dq++;
  	}
  }

  EXPORT_SYMBOL_GPL(raid6_datap_recov);

  #ifndef __KERNEL__
  /* Testing only */

  
  /* Recover two failed blocks. */
  void raid6_dual_recov(int disks, size_t bytes, int faila, int failb, void **ptrs)
  {
  	if ( faila > failb ) {
  		int tmp = faila;
  		faila = failb;
  		failb = tmp;
  	}
  
  	if ( failb == disks-1 ) {
  		if ( faila == disks-2 ) {
  			/* P+Q failure.  Just rebuild the syndrome. */
  			raid6_call.gen_syndrome(disks, bytes, ptrs);
  		} else {
  			/* data+Q failure.  Reconstruct data from P,
  			   then rebuild syndrome. */
  			/* NOT IMPLEMENTED - equivalent to RAID-5 */
  		}
  	} else {
  		if ( failb == disks-2 ) {
  			/* data+P failure. */
  			raid6_datap_recov(disks, bytes, faila, ptrs);
  		} else {
  			/* data+data failure. */
  			raid6_2data_recov(disks, bytes, faila, failb, ptrs);
  		}
  	}
  }
  
  #endif