inftlcore.c

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/*
 * inftlcore.c -- Linux driver for Inverse Flash Translation Layer (INFTL)
 *
 * Copyright © 2002, Greg Ungerer ([email protected])
 *
 * Based heavily on the nftlcore.c code which is:
 * Copyright © 1999 Machine Vision Holdings, Inc.
 * Copyright © 1999 David Woodhouse <[email protected]>
 *
 * 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.\n"
"Please use the new diskonchip driver under the NAND subsystem.\n");
        return;
    }

    pr_debug("INFTL: add_mtd for %s\n", 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\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;

    pr_debug("INFTL: remove_dev (i=%d)\n", 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)\n",
            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)\n",
                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\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;

    pr_debug("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] != 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\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.
     */
    pr_debug("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 && !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?\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).
     */
    pr_debug("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;

        /* 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)\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;

    pr_debug("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;
            pr_debug("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 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\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 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)\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.
     */
    pr_debug("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) {
            pr_debug("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;
        }

        pr_debug("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;

    pr_debug("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;

    pr_debug("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;

    pr_debug("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 && !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 <[email protected]>, David Woodhouse <[email protected]>, Fabrice Bellard <[email protected]> et al.");
MODULE_DESCRIPTION("Support code for Inverse Flash Translation Layer, used on M-Systems DiskOnChip 2000, Millennium and Millennium Plus");