/*
 * inftlcore.c -- Linux driver for Inverse Flash Translation Layer (INFTL)
 *
 * (C) Copyright 2002, Greg Ungerer (gerg@snapgear.com)
 *
 * Based heavily on the nftlcore.c code which is:
 * (c) 1999 Machine Vision Holdings, Inc.
 * Author: 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)
                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.\n"
"Please use the new diskonchip driver under the NAND subsystem.\n");
                return;
        }

        DEBUG(MTD_DEBUG_LEVEL3, "INFTL: add_mtd for %s\n", mtd->name);

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

        if (!inftl) {
                printk(KERN_WARNING "INFTL: Out of memory for data structures\n");
                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\n");
                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.\n", inftl->mbd.size);
                printk(KERN_WARNING "INFTL: using C:%d H:%d S:%d "
                        "(== 0x%lx sects)\n",
                        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\n", inftl->mbd.devnum + 'a');
#endif
        return;
}

static void inftl_remove_dev(struct mtd_blktrans_dev *dev)
{
        struct INFTLrecord *inftl = (void *)dev;

        DEBUG(MTD_DEBUG_LEVEL3, "INFTL: remove_dev (i=%d)\n", dev->devnum);

        del_mtd_blktrans_dev(dev);

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

/*
 * 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_OOB_PLACE;
        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_OOB_PLACE;
        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_OOB_PLACE;
        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;

        DEBUG(MTD_DEBUG_LEVEL3, "INFTL: INFTL_findfreeblock(inftl=%p,"
                "desperate=%d)\n", inftl, desperate);

        /*
         * Normally, we force a fold to happen before we run out of free
         * blocks completely.
         */
        if (!desperate && inftl->numfreeEUNs < 2) {
                DEBUG(MTD_DEBUG_LEVEL1, "INFTL: there are too few free "
                        "EUNs (%d)\n", inftl->numfreeEUNs);
                return 0xffff;
        }

        /* 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\n", 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;

        DEBUG(MTD_DEBUG_LEVEL3, "INFTL: INFTL_foldchain(inftl=%p,thisVUC=%d,"
                "pending=%d)\n", 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!\n", 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] != 0xffff) || 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\n",
                                        block, thisEUN, status);
                                break;
                        }
                }

                if (!silly--) {
                        printk(KERN_WARNING "INFTL: infinite loop in Virtual "
                                "Unit Chain 0x%x\n", 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.
         */
        DEBUG(MTD_DEBUG_LEVEL1, "INFTL: folding chain %d into unit %d\n",
                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 && ret != -EUCLEAN) {
                        ret = mtd->read(mtd,
                                        (inftl->EraseSize * BlockMap[block]) +
                                        (block * SECTORSIZE), SECTORSIZE,
                                        &retlen, movebuf);
                        if (ret != -EIO)
                                DEBUG(MTD_DEBUG_LEVEL1, "INFTL: error went "
                                      "away on retry?\n");
                }
                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).
         */
        DEBUG(MTD_DEBUG_LEVEL1, "INFTL: want to erase virtual chain %d\n",
                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;

                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->PUtable[prevEUN] = BLOCK_NIL;
                        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;

        DEBUG(MTD_DEBUG_LEVEL3, "INFTL: INFTL_makefreeblock(inftl=%p,"
                "pending=%d)\n", 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\n",
                                        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\n");
                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;

        DEBUG(MTD_DEBUG_LEVEL3, "INFTL: INFTL_findwriteunit(inftl=%p,"
                "block=%d)\n", 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;
                        DEBUG(MTD_DEBUG_LEVEL3, "INFTL: status of block %d in "
                                "EUN %d is %x\n", 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\n", thisVUC);
                                return 0xffff;
                        }

                        /* 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, 0xffff);

                        /*
                         * Hopefully we free something, lets try again.
                         * This time we are desperate...
                         */
                        DEBUG(MTD_DEBUG_LEVEL1, "INFTL: using desperate==1 "
                                "to find free EUN to accommodate write to "
                                "VUC %d\n", 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.\n");
#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\n", thisVUC);
        return 0xffff;
}

/*
 * 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;

        DEBUG(MTD_DEBUG_LEVEL3, "INFTL: INFTL_trydeletechain(inftl=%p,"
                "thisVUC=%d)\n", 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!\n", 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\n",
                                        block, thisEUN, status);
                        }
                }

                if (!silly--) {
                        printk(KERN_WARNING "INFTL: infinite loop in Virtual "
                                "Unit Chain 0x%x\n", 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.
         */
        DEBUG(MTD_DEBUG_LEVEL1, "INFTL: deleting empty VUC %d\n", thisVUC);

        for (;;) {
                u16 *prevEUN = &inftl->VUtable[thisVUC];
                thisEUN = *prevEUN;

                /* If the chain is all gone already, we're done */
                if (thisEUN == BLOCK_NIL) {
                        DEBUG(MTD_DEBUG_LEVEL2, "INFTL: Empty VUC %d for deletion was already absent\n", 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;
                }

                DEBUG(MTD_DEBUG_LEVEL3, "Deleting EUN %d from VUC %d\n",
                      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;

        DEBUG(MTD_DEBUG_LEVEL3, "INFTL: INFTL_deleteblock(inftl=%p,"
                "block=%d)\n", 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\n",
                                block, thisEUN, status);
                        break;
                }

                if (!silly--) {
                        printk(KERN_WARNING "INFTL: infinite loop in Virtual "
                                "Unit Chain 0x%x\n",
                                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;

        DEBUG(MTD_DEBUG_LEVEL3, "INFTL: inftl_writeblock(inftl=%p,block=%ld,"
                "buffer=%p)\n", 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\n");
                        /*
                         * 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;

        DEBUG(MTD_DEBUG_LEVEL3, "INFTL: inftl_readblock(inftl=%p,block=%ld,"
                "buffer=%p)\n", 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\n",
                                block, thisEUN, status);
                        break;
                }

                if (!silly--) {
                        printk(KERN_WARNING "INFTL: infinite loop in "
                                "Virtual Unit Chain 0x%lx\n",
                                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 && ret != -EUCLEAN)
                        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");