/*

   * inftlcore.c -- Linux driver for Inverse Flash Translation Layer (INFTL)
   *

   * Copyright © 2002, Greg Ungerer (gerg@snapgear.com)

   *
   * Based heavily on the nftlcore.c code which is:

   * Copyright © 1999 Machine Vision Holdings, Inc.
   * Copyright © 1999 David Woodhouse <dwmw2@infradead.org>

   *

   * 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; either version 2 of the License, or
   * (at your option) any later version.
   *
   * This program is distributed in the hope that it will be useful,
   * but WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   * GNU General Public License for more details.
   *
   * You should have received a copy of the GNU General Public License
   * along with this program; if not, write to the Free Software
   * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
   */

  #include <linux/kernel.h>
  #include <linux/module.h>
  #include <linux/delay.h>
  #include <linux/slab.h>
  #include <linux/sched.h>
  #include <linux/init.h>
  #include <linux/kmod.h>
  #include <linux/hdreg.h>
  #include <linux/mtd/mtd.h>
  #include <linux/mtd/nftl.h>
  #include <linux/mtd/inftl.h>

  #include <linux/mtd/nand.h>

  #include <asm/uaccess.h>
  #include <asm/errno.h>
  #include <asm/io.h>
  
  /*
   * Maximum number of loops while examining next block, to have a
   * chance to detect consistency problems (they should never happen
   * because of the checks done in the mounting.
   */
  #define MAX_LOOPS 10000

  static void inftl_add_mtd(struct mtd_blktrans_ops *tr, struct mtd_info *mtd)
  {
  	struct INFTLrecord *inftl;
  	unsigned long temp;

  	if (mtd->type != MTD_NANDFLASH || mtd->size > UINT_MAX)

  		return;
  	/* OK, this is moderately ugly.  But probably safe.  Alternatives? */
  	if (memcmp(mtd->name, "DiskOnChip", 10))
  		return;
  
  	if (!mtd->block_isbad) {
  		printk(KERN_ERR
  "INFTL no longer supports the old DiskOnChip drivers loaded via docprobe.
  "
  "Please use the new diskonchip driver under the NAND subsystem.
  ");
  		return;
  	}

  	pr_debug("INFTL: add_mtd for %s
  ", mtd->name);

  	inftl = kzalloc(sizeof(*inftl), GFP_KERNEL);

  	if (!inftl)

  		return;

  
  	inftl->mbd.mtd = mtd;
  	inftl->mbd.devnum = -1;

  	inftl->mbd.tr = tr;

  	if (INFTL_mount(inftl) < 0) {

  		printk(KERN_WARNING "INFTL: could not mount device
  ");
  		kfree(inftl);
  		return;

  	}

  
  	/* OK, it's a new one. Set up all the data structures. */
  
  	/* Calculate geometry */
  	inftl->cylinders = 1024;
  	inftl->heads = 16;
  
  	temp = inftl->cylinders * inftl->heads;
  	inftl->sectors = inftl->mbd.size / temp;
  	if (inftl->mbd.size % temp) {
  		inftl->sectors++;
  		temp = inftl->cylinders * inftl->sectors;
  		inftl->heads = inftl->mbd.size / temp;
  
  		if (inftl->mbd.size % temp) {
  			inftl->heads++;
  			temp = inftl->heads * inftl->sectors;
  			inftl->cylinders = inftl->mbd.size / temp;
  		}
  	}
  
  	if (inftl->mbd.size != inftl->heads * inftl->cylinders * inftl->sectors) {
  		/*

  		  Oh no we don't have

  		   mbd.size == heads * cylinders * sectors
  		*/
  		printk(KERN_WARNING "INFTL: cannot calculate a geometry to "
  		       "match size of 0x%lx.
  ", inftl->mbd.size);
  		printk(KERN_WARNING "INFTL: using C:%d H:%d S:%d "
  			"(== 0x%lx sects)
  ",

  			inftl->cylinders, inftl->heads , inftl->sectors,

  			(long)inftl->cylinders * (long)inftl->heads *
  			(long)inftl->sectors );
  	}
  
  	if (add_mtd_blktrans_dev(&inftl->mbd)) {

  		kfree(inftl->PUtable);
  		kfree(inftl->VUtable);

  		kfree(inftl);
  		return;
  	}
  #ifdef PSYCHO_DEBUG

  	printk(KERN_INFO "INFTL: Found new inftl%c
  ", inftl->mbd.devnum + 'a');

  #endif
  	return;
  }
  
  static void inftl_remove_dev(struct mtd_blktrans_dev *dev)
  {
  	struct INFTLrecord *inftl = (void *)dev;

  	pr_debug("INFTL: remove_dev (i=%d)
  ", dev->devnum);

  
  	del_mtd_blktrans_dev(dev);

  	kfree(inftl->PUtable);
  	kfree(inftl->VUtable);

  }
  
  /*
   * Actual INFTL access routines.
   */
  
  /*

   * Read oob data from flash
   */
  int inftl_read_oob(struct mtd_info *mtd, loff_t offs, size_t len,
  		   size_t *retlen, uint8_t *buf)
  {
  	struct mtd_oob_ops ops;
  	int res;

  	ops.mode = MTD_OPS_PLACE_OOB;

  	ops.ooboffs = offs & (mtd->writesize - 1);
  	ops.ooblen = len;
  	ops.oobbuf = buf;
  	ops.datbuf = NULL;

  	res = mtd_read_oob(mtd, offs & ~(mtd->writesize - 1), &ops);

  	*retlen = ops.oobretlen;

  	return res;
  }
  
  /*
   * Write oob data to flash
   */
  int inftl_write_oob(struct mtd_info *mtd, loff_t offs, size_t len,
  		    size_t *retlen, uint8_t *buf)
  {
  	struct mtd_oob_ops ops;
  	int res;

  	ops.mode = MTD_OPS_PLACE_OOB;

  	ops.ooboffs = offs & (mtd->writesize - 1);
  	ops.ooblen = len;
  	ops.oobbuf = buf;
  	ops.datbuf = NULL;

  	res = mtd_write_oob(mtd, offs & ~(mtd->writesize - 1), &ops);

  	*retlen = ops.oobretlen;

  	return res;
  }
  
  /*
   * Write data and oob to flash
   */
  static int inftl_write(struct mtd_info *mtd, loff_t offs, size_t len,
  		       size_t *retlen, uint8_t *buf, uint8_t *oob)
  {
  	struct mtd_oob_ops ops;
  	int res;

  	ops.mode = MTD_OPS_PLACE_OOB;

  	ops.ooboffs = offs;
  	ops.ooblen = mtd->oobsize;
  	ops.oobbuf = oob;
  	ops.datbuf = buf;
  	ops.len = len;

  	res = mtd_write_oob(mtd, offs & ~(mtd->writesize - 1), &ops);

  	*retlen = ops.retlen;
  	return res;
  }
  
  /*

   * INFTL_findfreeblock: Find a free Erase Unit on the INFTL partition.
   *	This function is used when the give Virtual Unit Chain.
   */
  static u16 INFTL_findfreeblock(struct INFTLrecord *inftl, int desperate)
  {
  	u16 pot = inftl->LastFreeEUN;
  	int silly = inftl->nb_blocks;

  	pr_debug("INFTL: INFTL_findfreeblock(inftl=%p,desperate=%d)
  ",
  			inftl, desperate);

  
  	/*
  	 * Normally, we force a fold to happen before we run out of free
  	 * blocks completely.
  	 */
  	if (!desperate && inftl->numfreeEUNs < 2) {

  		pr_debug("INFTL: there are too few free EUNs (%d)
  ",
  				inftl->numfreeEUNs);

  		return BLOCK_NIL;

  	}
  
  	/* Scan for a free block */
  	do {
  		if (inftl->PUtable[pot] == BLOCK_FREE) {
  			inftl->LastFreeEUN = pot;
  			return pot;
  		}
  
  		if (++pot > inftl->lastEUN)
  			pot = 0;
  
  		if (!silly--) {
  			printk(KERN_WARNING "INFTL: no free blocks found!  "
  				"EUN range = %d - %d
  ", 0, inftl->LastFreeEUN);
  			return BLOCK_NIL;
  		}
  	} while (pot != inftl->LastFreeEUN);
  
  	return BLOCK_NIL;
  }
  
  static u16 INFTL_foldchain(struct INFTLrecord *inftl, unsigned thisVUC, unsigned pendingblock)
  {
  	u16 BlockMap[MAX_SECTORS_PER_UNIT];
  	unsigned char BlockDeleted[MAX_SECTORS_PER_UNIT];
  	unsigned int thisEUN, prevEUN, status;

  	struct mtd_info *mtd = inftl->mbd.mtd;

  	int block, silly;
  	unsigned int targetEUN;
  	struct inftl_oob oob;

  	size_t retlen;

  	pr_debug("INFTL: INFTL_foldchain(inftl=%p,thisVUC=%d,pending=%d)
  ",
  			inftl, thisVUC, pendingblock);

  
  	memset(BlockMap, 0xff, sizeof(BlockMap));
  	memset(BlockDeleted, 0, sizeof(BlockDeleted));
  
  	thisEUN = targetEUN = inftl->VUtable[thisVUC];
  
  	if (thisEUN == BLOCK_NIL) {
  		printk(KERN_WARNING "INFTL: trying to fold non-existent "
  		       "Virtual Unit Chain %d!
  ", thisVUC);
  		return BLOCK_NIL;
  	}

  	/*
  	 * Scan to find the Erase Unit which holds the actual data for each
  	 * 512-byte block within the Chain.
  	 */

  	silly = MAX_LOOPS;

  	while (thisEUN < inftl->nb_blocks) {
  		for (block = 0; block < inftl->EraseSize/SECTORSIZE; block ++) {

  			if ((BlockMap[block] != BLOCK_NIL) ||
  			    BlockDeleted[block])

  				continue;

  			if (inftl_read_oob(mtd, (thisEUN * inftl->EraseSize)
  					   + (block * SECTORSIZE), 16, &retlen,
  					   (char *)&oob) < 0)

  				status = SECTOR_IGNORE;
  			else

  				status = oob.b.Status | oob.b.Status1;

  
  			switch(status) {
  			case SECTOR_FREE:
  			case SECTOR_IGNORE:
  				break;
  			case SECTOR_USED:
  				BlockMap[block] = thisEUN;
  				continue;
  			case SECTOR_DELETED:
  				BlockDeleted[block] = 1;
  				continue;
  			default:
  				printk(KERN_WARNING "INFTL: unknown status "
  					"for block %d in EUN %d: %x
  ",
  					block, thisEUN, status);
  				break;
  			}
  		}
  
  		if (!silly--) {
  			printk(KERN_WARNING "INFTL: infinite loop in Virtual "
  				"Unit Chain 0x%x
  ", thisVUC);
  			return BLOCK_NIL;
  		}

  		thisEUN = inftl->PUtable[thisEUN];
  	}
  
  	/*
  	 * OK. We now know the location of every block in the Virtual Unit
  	 * Chain, and the Erase Unit into which we are supposed to be copying.
  	 * Go for it.
  	 */

  	pr_debug("INFTL: folding chain %d into unit %d
  ", thisVUC, targetEUN);

  
  	for (block = 0; block < inftl->EraseSize/SECTORSIZE ; block++) {
  		unsigned char movebuf[SECTORSIZE];
  		int ret;
  
  		/*
  		 * If it's in the target EUN already, or if it's pending write,
  		 * do nothing.
  		 */
  		if (BlockMap[block] == targetEUN || (pendingblock ==
  		    (thisVUC * (inftl->EraseSize / SECTORSIZE) + block))) {
  			continue;
  		}

  		/*

  		 * Copy only in non free block (free blocks can only
                   * happen in case of media errors or deleted blocks).
  		 */

  		if (BlockMap[block] == BLOCK_NIL)
  			continue;

  		ret = mtd_read(mtd,
  			       (inftl->EraseSize * BlockMap[block]) + (block * SECTORSIZE),
  			       SECTORSIZE,
  			       &retlen,
  			       movebuf);

  		if (ret < 0 && !mtd_is_bitflip(ret)) {

  			ret = mtd_read(mtd,
  				       (inftl->EraseSize * BlockMap[block]) + (block * SECTORSIZE),
  				       SECTORSIZE,
  				       &retlen,
  				       movebuf);

  			if (ret != -EIO)

  				pr_debug("INFTL: error went away on retry?
  ");

  		}
  		memset(&oob, 0xff, sizeof(struct inftl_oob));
  		oob.b.Status = oob.b.Status1 = SECTOR_USED;

  		inftl_write(inftl->mbd.mtd, (inftl->EraseSize * targetEUN) +
  			    (block * SECTORSIZE), SECTORSIZE, &retlen,
  			    movebuf, (char *)&oob);

  	}
  
  	/*
  	 * Newest unit in chain now contains data from _all_ older units.
  	 * So go through and erase each unit in chain, oldest first. (This
  	 * is important, by doing oldest first if we crash/reboot then it
  	 * it is relatively simple to clean up the mess).
  	 */

  	pr_debug("INFTL: want to erase virtual chain %d
  ", thisVUC);

  
  	for (;;) {
  		/* Find oldest unit in chain. */
  		thisEUN = inftl->VUtable[thisVUC];
  		prevEUN = BLOCK_NIL;
  		while (inftl->PUtable[thisEUN] != BLOCK_NIL) {
  			prevEUN = thisEUN;
  			thisEUN = inftl->PUtable[thisEUN];
  		}
  
  		/* Check if we are all done */
  		if (thisEUN == targetEUN)
  			break;

  		/* Unlink the last block from the chain. */
  		inftl->PUtable[prevEUN] = BLOCK_NIL;
  
  		/* Now try to erase it. */

  		if (INFTL_formatblock(inftl, thisEUN) < 0) {

  			/*
  			 * Could not erase : mark block as reserved.
  			 */
  			inftl->PUtable[thisEUN] = BLOCK_RESERVED;

  		} else {

  			/* Correctly erased : mark it as free */
  			inftl->PUtable[thisEUN] = BLOCK_FREE;

  			inftl->numfreeEUNs++;

  		}

  	}
  
  	return targetEUN;
  }
  
  static u16 INFTL_makefreeblock(struct INFTLrecord *inftl, unsigned pendingblock)
  {
  	/*

  	 * This is the part that needs some cleverness applied.

  	 * For now, I'm doing the minimum applicable to actually
  	 * get the thing to work.
  	 * Wear-levelling and other clever stuff needs to be implemented
  	 * and we also need to do some assessment of the results when
  	 * the system loses power half-way through the routine.
  	 */
  	u16 LongestChain = 0;
  	u16 ChainLength = 0, thislen;
  	u16 chain, EUN;

  	pr_debug("INFTL: INFTL_makefreeblock(inftl=%p,"

  		"pending=%d)
  ", inftl, pendingblock);
  
  	for (chain = 0; chain < inftl->nb_blocks; chain++) {
  		EUN = inftl->VUtable[chain];
  		thislen = 0;
  
  		while (EUN <= inftl->lastEUN) {
  			thislen++;
  			EUN = inftl->PUtable[EUN];
  			if (thislen > 0xff00) {
  				printk(KERN_WARNING "INFTL: endless loop in "
  					"Virtual Chain %d: Unit %x
  ",
  					chain, EUN);
  				/*
  				 * Actually, don't return failure.
  				 * Just ignore this chain and get on with it.
  				 */
  				thislen = 0;
  				break;
  			}
  		}
  
  		if (thislen > ChainLength) {
  			ChainLength = thislen;
  			LongestChain = chain;
  		}
  	}
  
  	if (ChainLength < 2) {
  		printk(KERN_WARNING "INFTL: no Virtual Unit Chains available "
  			"for folding. Failing request
  ");
  		return BLOCK_NIL;
  	}
  
  	return INFTL_foldchain(inftl, LongestChain, pendingblock);
  }
  
  static int nrbits(unsigned int val, int bitcount)
  {
  	int i, total = 0;
  
  	for (i = 0; (i < bitcount); i++)
  		total += (((0x1 << i) & val) ? 1 : 0);
  	return total;
  }
  
  /*

   * INFTL_findwriteunit: Return the unit number into which we can write

   *                      for this block. Make it available if it isn't already.
   */
  static inline u16 INFTL_findwriteunit(struct INFTLrecord *inftl, unsigned block)
  {
  	unsigned int thisVUC = block / (inftl->EraseSize / SECTORSIZE);
  	unsigned int thisEUN, writeEUN, prev_block, status;
  	unsigned long blockofs = (block * SECTORSIZE) & (inftl->EraseSize -1);

  	struct mtd_info *mtd = inftl->mbd.mtd;

  	struct inftl_oob oob;
  	struct inftl_bci bci;
  	unsigned char anac, nacs, parity;
  	size_t retlen;
  	int silly, silly2 = 3;

  	pr_debug("INFTL: INFTL_findwriteunit(inftl=%p,block=%d)
  ",
  			inftl, block);

  
  	do {
  		/*
  		 * Scan the media to find a unit in the VUC which has
  		 * a free space for the block in question.
  		 */
  		writeEUN = BLOCK_NIL;
  		thisEUN = inftl->VUtable[thisVUC];
  		silly = MAX_LOOPS;
  
  		while (thisEUN <= inftl->lastEUN) {

  			inftl_read_oob(mtd, (thisEUN * inftl->EraseSize) +
  				       blockofs, 8, &retlen, (char *)&bci);

  			status = bci.Status | bci.Status1;

  			pr_debug("INFTL: status of block %d in EUN %d is %x
  ",
  					block , writeEUN, status);

  
  			switch(status) {
  			case SECTOR_FREE:
  				writeEUN = thisEUN;
  				break;
  			case SECTOR_DELETED:
  			case SECTOR_USED:
  				/* Can't go any further */
  				goto hitused;
  			case SECTOR_IGNORE:
  				break;
  			default:
  				/*
  				 * Invalid block. Don't use it any more.
  				 * Must implement.
  				 */

  				break;

  			}

  
  			if (!silly--) {

  				printk(KERN_WARNING "INFTL: infinite loop in "
  					"Virtual Unit Chain 0x%x
  ", thisVUC);

  				return BLOCK_NIL;

  			}
  
  			/* Skip to next block in chain */
  			thisEUN = inftl->PUtable[thisEUN];
  		}
  
  hitused:
  		if (writeEUN != BLOCK_NIL)
  			return writeEUN;
  
  
  		/*

  		 * OK. We didn't find one in the existing chain, or there

  		 * is no existing chain. Allocate a new one.
  		 */
  		writeEUN = INFTL_findfreeblock(inftl, 0);
  
  		if (writeEUN == BLOCK_NIL) {
  			/*
  			 * That didn't work - there were no free blocks just
  			 * waiting to be picked up. We're going to have to fold
  			 * a chain to make room.
  			 */

  			thisEUN = INFTL_makefreeblock(inftl, block);

  
  			/*
  			 * Hopefully we free something, lets try again.
  			 * This time we are desperate...
  			 */

  			pr_debug("INFTL: using desperate==1 to find free EUN "
  					"to accommodate write to VUC %d
  ",
  					thisVUC);

  			writeEUN = INFTL_findfreeblock(inftl, 1);
  			if (writeEUN == BLOCK_NIL) {
  				/*
  				 * Ouch. This should never happen - we should

  				 * always be able to make some room somehow.
  				 * If we get here, we've allocated more storage

  				 * space than actual media, or our makefreeblock
  				 * routine is missing something.
  				 */
  				printk(KERN_WARNING "INFTL: cannot make free "
  					"space.
  ");
  #ifdef DEBUG
  				INFTL_dumptables(inftl);
  				INFTL_dumpVUchains(inftl);
  #endif
  				return BLOCK_NIL;

  			}

  		}
  
  		/*
  		 * Insert new block into virtual chain. Firstly update the
  		 * block headers in flash...
  		 */
  		anac = 0;
  		nacs = 0;
  		thisEUN = inftl->VUtable[thisVUC];
  		if (thisEUN != BLOCK_NIL) {

  			inftl_read_oob(mtd, thisEUN * inftl->EraseSize
  				       + 8, 8, &retlen, (char *)&oob.u);

  			anac = oob.u.a.ANAC + 1;
  			nacs = oob.u.a.NACs + 1;
  		}
  
  		prev_block = inftl->VUtable[thisVUC];
  		if (prev_block < inftl->nb_blocks)
  			prev_block -= inftl->firstEUN;
  
  		parity = (nrbits(thisVUC, 16) & 0x1) ? 0x1 : 0;
  		parity |= (nrbits(prev_block, 16) & 0x1) ? 0x2 : 0;
  		parity |= (nrbits(anac, 8) & 0x1) ? 0x4 : 0;
  		parity |= (nrbits(nacs, 8) & 0x1) ? 0x8 : 0;

  		oob.u.a.virtualUnitNo = cpu_to_le16(thisVUC);
  		oob.u.a.prevUnitNo = cpu_to_le16(prev_block);
  		oob.u.a.ANAC = anac;
  		oob.u.a.NACs = nacs;
  		oob.u.a.parityPerField = parity;
  		oob.u.a.discarded = 0xaa;

  		inftl_write_oob(mtd, writeEUN * inftl->EraseSize + 8, 8,
  				&retlen, (char *)&oob.u);

  
  		/* Also back up header... */
  		oob.u.b.virtualUnitNo = cpu_to_le16(thisVUC);
  		oob.u.b.prevUnitNo = cpu_to_le16(prev_block);
  		oob.u.b.ANAC = anac;
  		oob.u.b.NACs = nacs;
  		oob.u.b.parityPerField = parity;
  		oob.u.b.discarded = 0xaa;

  		inftl_write_oob(mtd, writeEUN * inftl->EraseSize +
  				SECTORSIZE * 4 + 8, 8, &retlen, (char *)&oob.u);

  
  		inftl->PUtable[writeEUN] = inftl->VUtable[thisVUC];
  		inftl->VUtable[thisVUC] = writeEUN;
  
  		inftl->numfreeEUNs--;
  		return writeEUN;
  
  	} while (silly2--);
  
  	printk(KERN_WARNING "INFTL: error folding to make room for Virtual "
  		"Unit Chain 0x%x
  ", thisVUC);

  	return BLOCK_NIL;

  }
  
  /*
   * Given a Virtual Unit Chain, see if it can be deleted, and if so do it.
   */
  static void INFTL_trydeletechain(struct INFTLrecord *inftl, unsigned thisVUC)
  {

  	struct mtd_info *mtd = inftl->mbd.mtd;

  	unsigned char BlockUsed[MAX_SECTORS_PER_UNIT];
  	unsigned char BlockDeleted[MAX_SECTORS_PER_UNIT];
  	unsigned int thisEUN, status;
  	int block, silly;
  	struct inftl_bci bci;
  	size_t retlen;

  	pr_debug("INFTL: INFTL_trydeletechain(inftl=%p,"

  		"thisVUC=%d)
  ", inftl, thisVUC);
  
  	memset(BlockUsed, 0, sizeof(BlockUsed));
  	memset(BlockDeleted, 0, sizeof(BlockDeleted));
  
  	thisEUN = inftl->VUtable[thisVUC];
  	if (thisEUN == BLOCK_NIL) {
  		printk(KERN_WARNING "INFTL: trying to delete non-existent "
  		       "Virtual Unit Chain %d!
  ", thisVUC);
  		return;
  	}

  	/*
  	 * Scan through the Erase Units to determine whether any data is in
  	 * each of the 512-byte blocks within the Chain.
  	 */
  	silly = MAX_LOOPS;
  	while (thisEUN < inftl->nb_blocks) {
  		for (block = 0; block < inftl->EraseSize/SECTORSIZE; block++) {
  			if (BlockUsed[block] || BlockDeleted[block])
  				continue;

  			if (inftl_read_oob(mtd, (thisEUN * inftl->EraseSize)
  					   + (block * SECTORSIZE), 8 , &retlen,

  					  (char *)&bci) < 0)

  				status = SECTOR_IGNORE;
  			else
  				status = bci.Status | bci.Status1;
  
  			switch(status) {
  			case SECTOR_FREE:
  			case SECTOR_IGNORE:
  				break;
  			case SECTOR_USED:
  				BlockUsed[block] = 1;
  				continue;
  			case SECTOR_DELETED:
  				BlockDeleted[block] = 1;
  				continue;
  			default:
  				printk(KERN_WARNING "INFTL: unknown status "
  					"for block %d in EUN %d: 0x%x
  ",
  					block, thisEUN, status);
  			}
  		}
  
  		if (!silly--) {
  			printk(KERN_WARNING "INFTL: infinite loop in Virtual "
  				"Unit Chain 0x%x
  ", thisVUC);
  			return;
  		}

  		thisEUN = inftl->PUtable[thisEUN];
  	}
  
  	for (block = 0; block < inftl->EraseSize/SECTORSIZE; block++)
  		if (BlockUsed[block])
  			return;
  
  	/*
  	 * For each block in the chain free it and make it available
  	 * for future use. Erase from the oldest unit first.
  	 */

  	pr_debug("INFTL: deleting empty VUC %d
  ", thisVUC);

  
  	for (;;) {
  		u16 *prevEUN = &inftl->VUtable[thisVUC];
  		thisEUN = *prevEUN;
  
  		/* If the chain is all gone already, we're done */
  		if (thisEUN == BLOCK_NIL) {

  			pr_debug("INFTL: Empty VUC %d for deletion was already absent
  ", thisEUN);

  			return;
  		}
  
  		/* Find oldest unit in chain. */
  		while (inftl->PUtable[thisEUN] != BLOCK_NIL) {
  			BUG_ON(thisEUN >= inftl->nb_blocks);
  
  			prevEUN = &inftl->PUtable[thisEUN];
  			thisEUN = *prevEUN;
  		}

  		pr_debug("Deleting EUN %d from VUC %d
  ",

  		      thisEUN, thisVUC);

  		if (INFTL_formatblock(inftl, thisEUN) < 0) {

  			/*
  			 * Could not erase : mark block as reserved.
  			 */
  			inftl->PUtable[thisEUN] = BLOCK_RESERVED;

  		} else {

  			/* Correctly erased : mark it as free */
  			inftl->PUtable[thisEUN] = BLOCK_FREE;
  			inftl->numfreeEUNs++;
  		}
  
  		/* Now sort out whatever was pointing to it... */
  		*prevEUN = BLOCK_NIL;
  
  		/* Ideally we'd actually be responsive to new
  		   requests while we're doing this -- if there's
  		   free space why should others be made to wait? */
  		cond_resched();
  	}
  
  	inftl->VUtable[thisVUC] = BLOCK_NIL;
  }
  
  static int INFTL_deleteblock(struct INFTLrecord *inftl, unsigned block)
  {
  	unsigned int thisEUN = inftl->VUtable[block / (inftl->EraseSize / SECTORSIZE)];
  	unsigned long blockofs = (block * SECTORSIZE) & (inftl->EraseSize - 1);

  	struct mtd_info *mtd = inftl->mbd.mtd;

  	unsigned int status;
  	int silly = MAX_LOOPS;
  	size_t retlen;
  	struct inftl_bci bci;

  	pr_debug("INFTL: INFTL_deleteblock(inftl=%p,"

  		"block=%d)
  ", inftl, block);
  
  	while (thisEUN < inftl->nb_blocks) {

  		if (inftl_read_oob(mtd, (thisEUN * inftl->EraseSize) +
  				   blockofs, 8, &retlen, (char *)&bci) < 0)

  			status = SECTOR_IGNORE;
  		else
  			status = bci.Status | bci.Status1;
  
  		switch (status) {
  		case SECTOR_FREE:
  		case SECTOR_IGNORE:
  			break;
  		case SECTOR_DELETED:
  			thisEUN = BLOCK_NIL;
  			goto foundit;
  		case SECTOR_USED:
  			goto foundit;
  		default:
  			printk(KERN_WARNING "INFTL: unknown status for "
  				"block %d in EUN %d: 0x%x
  ",
  				block, thisEUN, status);
  			break;
  		}
  
  		if (!silly--) {
  			printk(KERN_WARNING "INFTL: infinite loop in Virtual "
  				"Unit Chain 0x%x
  ",
  				block / (inftl->EraseSize / SECTORSIZE));
  			return 1;
  		}
  		thisEUN = inftl->PUtable[thisEUN];
  	}
  
  foundit:
  	if (thisEUN != BLOCK_NIL) {
  		loff_t ptr = (thisEUN * inftl->EraseSize) + blockofs;

  		if (inftl_read_oob(mtd, ptr, 8, &retlen, (char *)&bci) < 0)

  			return -EIO;
  		bci.Status = bci.Status1 = SECTOR_DELETED;

  		if (inftl_write_oob(mtd, ptr, 8, &retlen, (char *)&bci) < 0)

  			return -EIO;
  		INFTL_trydeletechain(inftl, block / (inftl->EraseSize / SECTORSIZE));
  	}
  	return 0;
  }

  static int inftl_writeblock(struct mtd_blktrans_dev *mbd, unsigned long block,

  			    char *buffer)
  {
  	struct INFTLrecord *inftl = (void *)mbd;
  	unsigned int writeEUN;
  	unsigned long blockofs = (block * SECTORSIZE) & (inftl->EraseSize - 1);
  	size_t retlen;
  	struct inftl_oob oob;
  	char *p, *pend;

  	pr_debug("INFTL: inftl_writeblock(inftl=%p,block=%ld,"

  		"buffer=%p)
  ", inftl, block, buffer);
  
  	/* Is block all zero? */
  	pend = buffer + SECTORSIZE;
  	for (p = buffer; p < pend && !*p; p++)
  		;
  
  	if (p < pend) {
  		writeEUN = INFTL_findwriteunit(inftl, block);
  
  		if (writeEUN == BLOCK_NIL) {
  			printk(KERN_WARNING "inftl_writeblock(): cannot find "
  				"block to write to
  ");
  			/*
  			 * If we _still_ haven't got a block to use,
  			 * we're screwed.
  			 */
  			return 1;
  		}
  
  		memset(&oob, 0xff, sizeof(struct inftl_oob));
  		oob.b.Status = oob.b.Status1 = SECTOR_USED;

  		inftl_write(inftl->mbd.mtd, (writeEUN * inftl->EraseSize) +
  			    blockofs, SECTORSIZE, &retlen, (char *)buffer,
  			    (char *)&oob);

  		/*
  		 * need to write SECTOR_USED flags since they are not written
  		 * in mtd_writeecc
  		 */
  	} else {
  		INFTL_deleteblock(inftl, block);
  	}
  
  	return 0;
  }
  
  static int inftl_readblock(struct mtd_blktrans_dev *mbd, unsigned long block,
  			   char *buffer)
  {
  	struct INFTLrecord *inftl = (void *)mbd;
  	unsigned int thisEUN = inftl->VUtable[block / (inftl->EraseSize / SECTORSIZE)];
  	unsigned long blockofs = (block * SECTORSIZE) & (inftl->EraseSize - 1);

  	struct mtd_info *mtd = inftl->mbd.mtd;

  	unsigned int status;

  	int silly = MAX_LOOPS;

  	struct inftl_bci bci;

  	size_t retlen;

  	pr_debug("INFTL: inftl_readblock(inftl=%p,block=%ld,"

  		"buffer=%p)
  ", inftl, block, buffer);
  
  	while (thisEUN < inftl->nb_blocks) {

  		if (inftl_read_oob(mtd, (thisEUN * inftl->EraseSize) +

  				  blockofs, 8, &retlen, (char *)&bci) < 0)

  			status = SECTOR_IGNORE;
  		else
  			status = bci.Status | bci.Status1;
  
  		switch (status) {
  		case SECTOR_DELETED:
  			thisEUN = BLOCK_NIL;
  			goto foundit;
  		case SECTOR_USED:
  			goto foundit;
  		case SECTOR_FREE:
  		case SECTOR_IGNORE:
  			break;
  		default:
  			printk(KERN_WARNING "INFTL: unknown status for "
  				"block %ld in EUN %d: 0x%04x
  ",
  				block, thisEUN, status);
  			break;
  		}
  
  		if (!silly--) {
  			printk(KERN_WARNING "INFTL: infinite loop in "
  				"Virtual Unit Chain 0x%lx
  ",
  				block / (inftl->EraseSize / SECTORSIZE));
  			return 1;
  		}
  
  		thisEUN = inftl->PUtable[thisEUN];
  	}
  
  foundit:
  	if (thisEUN == BLOCK_NIL) {
  		/* The requested block is not on the media, return all 0x00 */
  		memset(buffer, 0, SECTORSIZE);
  	} else {

  		size_t retlen;

  		loff_t ptr = (thisEUN * inftl->EraseSize) + blockofs;

  		int ret = mtd_read(mtd, ptr, SECTORSIZE, &retlen, buffer);

  
  		/* Handle corrected bit flips gracefully */

  		if (ret < 0 && !mtd_is_bitflip(ret))

  			return -EIO;
  	}
  	return 0;
  }
  
  static int inftl_getgeo(struct mtd_blktrans_dev *dev, struct hd_geometry *geo)
  {
  	struct INFTLrecord *inftl = (void *)dev;
  
  	geo->heads = inftl->heads;
  	geo->sectors = inftl->sectors;
  	geo->cylinders = inftl->cylinders;
  
  	return 0;
  }
  
  static struct mtd_blktrans_ops inftl_tr = {
  	.name		= "inftl",
  	.major		= INFTL_MAJOR,
  	.part_bits	= INFTL_PARTN_BITS,

  	.blksize 	= 512,

  	.getgeo		= inftl_getgeo,
  	.readsect	= inftl_readblock,
  	.writesect	= inftl_writeblock,
  	.add_mtd	= inftl_add_mtd,
  	.remove_dev	= inftl_remove_dev,
  	.owner		= THIS_MODULE,
  };

  static int __init init_inftl(void)
  {

  	return register_mtd_blktrans(&inftl_tr);
  }
  
  static void __exit cleanup_inftl(void)
  {
  	deregister_mtd_blktrans(&inftl_tr);
  }
  
  module_init(init_inftl);
  module_exit(cleanup_inftl);
  
  MODULE_LICENSE("GPL");
  MODULE_AUTHOR("Greg Ungerer <gerg@snapgear.com>, David Woodhouse <dwmw2@infradead.org>, Fabrice Bellard <fabrice.bellard@netgem.com> et al.");
  MODULE_DESCRIPTION("Support code for Inverse Flash Translation Layer, used on M-Systems DiskOnChip 2000, Millennium and Millennium Plus");