/*-
 * Copyright (c) 1998 Michael Smith <msmith@freebsd.org>
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 * $FreeBSD: src/sys/boot/i386/libi386/biosdisk.c,v 1.45 2004/09/21 06:46:44 wes Exp $
 */

/*
 * BIOS disk device handling.
 * 
 * Ideas and algorithms from:
 *
 * - NetBSD libi386/biosdisk.c
 * - FreeBSD biosboot/disk.c
 *
 */

#include <stand.h>

#include <sys/disklabel32.h>
#include <sys/disklabel64.h>
#include <sys/diskmbr.h>
#include <sys/dtype.h>
#include <machine/bootinfo.h>
#include <machine/psl.h>

#include <stdarg.h>

#include <bootstrap.h>
#include <btxv86.h>
#include "libi386.h"

#define BIOS_NUMDRIVES          0x475
#define BIOSDISK_SECSIZE        512
#define BUFSIZE                 (4 * BIOSDISK_SECSIZE)
#define MAXBDDEV                MAXDEV

#define DT_ATAPI                0x10            /* disk type for ATAPI floppies */
#define WDMAJOR                 0               /* major numbers for devices we frontend for */
#define WFDMAJOR                1
#define FDMAJOR                 2
#define DAMAJOR                 4

#ifdef DISK_DEBUG
# define DEBUG(fmt, args...)    printf("%s: " fmt "\n" , __func__ , ## args)
#else
# define DEBUG(fmt, args...)
#endif

struct open_disk {
    int                 od_dkunit;              /* disk unit number */
    int                 od_unit;                /* BIOS unit number */
    int                 od_cyl;                 /* BIOS geometry */
    int                 od_hds;
    int                 od_sec;
    int                 od_boff;                /* block offset from beginning of BIOS disk */
    int                 od_flags;
#define BD_MODEINT13            0x0000
#define BD_MODEEDD1             0x0001
#define BD_MODEEDD3             0x0002
#define BD_MODEMASK             0x0003
#define BD_FLOPPY               0x0004
#define BD_LABELOK              0x0008
#define BD_PARTTABOK            0x0010
    union {
        struct disklabel32              od_disklabel;
        struct disklabel64              od_disklabel64;
    };
    int                         od_nslices;     /* slice count */
    struct dos_partition        od_slicetab[NEXTDOSPART];
};

/*
 * List of BIOS devices, translation from disk unit number to
 * BIOS unit number.
 */
static struct bdinfo
{
    int         bd_unit;                /* BIOS unit number */
    int         bd_flags;
    int         bd_type;                /* BIOS 'drive type' (floppy only) */
} bdinfo [MAXBDDEV];
static int nbdinfo = 0;

static int      bd_getgeom(struct open_disk *od);
static int      bd_read(struct open_disk *od, daddr_t dblk, int blks,
                    caddr_t dest);
static int      bd_write(struct open_disk *od, daddr_t dblk, int blks,
                    caddr_t dest);

static int      bd_int13probe(struct bdinfo *bd);

static void     bd_printslice(struct open_disk *od, struct dos_partition *dp,
                    char *prefix, int verbose);
static void     bd_printbsdslice(struct open_disk *od, daddr_t offset,
                    char *prefix, int verbose);

static int      bd_init(void);
static int      bd_strategy(void *devdata, int flag, daddr_t dblk,
                    size_t size, char *buf, size_t *rsize);
static int      bd_realstrategy(void *devdata, int flag, daddr_t dblk,
                    size_t size, char *buf, size_t *rsize);
static int      bd_open(struct open_file *f, ...);
static int      bd_close(struct open_file *f);
static void     bd_print(int verbose);

struct devsw biosdisk = {
    "disk", 
    DEVT_DISK, 
    bd_init,
    bd_strategy, 
    bd_open, 
    bd_close, 
    noioctl,
    bd_print,
    NULL
};

static int      bd_opendisk(struct open_disk **odp, struct i386_devdesc *dev);
static void     bd_closedisk(struct open_disk *od);
static int      bd_bestslice(struct open_disk *od);
static void     bd_chainextended(struct open_disk *od, u_int32_t base,
                                        u_int32_t offset);

/* also used by CD code */
char    __aligned(16) bounce_base[BOUNCEBUF_SIZE];


/*
 * Translate between BIOS device numbers and our private unit numbers.
 */
int
bd_bios2unit(int biosdev)
{
    int         i;
    
    DEBUG("looking for bios device 0x%x", biosdev);
    for (i = 0; i < nbdinfo; i++) {
        DEBUG("bd unit %d is BIOS device 0x%x", i, bdinfo[i].bd_unit);
        if (bdinfo[i].bd_unit == biosdev)
            return(i);
    }
    return(-1);
}

int
bd_unit2bios(int unit)
{
    if ((unit >= 0) && (unit < nbdinfo))
        return(bdinfo[unit].bd_unit);
    return(-1);
}

/*    
 * Quiz the BIOS for disk devices, save a little info about them.
 */
static int
bd_init(void) 
{
    int base, unit, nfd = 0;

    /* sequence 0, 0x80 */
    for (base = 0; base <= 0x80; base += 0x80) {
        for (unit = base; (nbdinfo < MAXBDDEV); unit++) {
            /* check the BIOS equipment list for number of fixed disks */
            if((base == 0x80) &&
               (nfd >= *(unsigned char *)PTOV(BIOS_NUMDRIVES)))
                break;

            bdinfo[nbdinfo].bd_unit = unit;
            bdinfo[nbdinfo].bd_flags = (unit < 0x80) ? BD_FLOPPY : 0;

            if (!bd_int13probe(&bdinfo[nbdinfo]))
                break;

            /* XXX we need "disk aliases" to make this simpler */
            printf("BIOS drive %c: is disk%d\n", 
                   (unit < 0x80) ? ('A' + unit) : ('C' + unit - 0x80), nbdinfo);
            nbdinfo++;
            if (base == 0x80)
                nfd++;
        }
    }
    return(0);
}

/*
 * Try to detect a device supported by the legacy int13 BIOS
 */
static int
bd_int13probe(struct bdinfo *bd)
{
    v86.ctl = V86_FLAGS;
    v86.addr = 0x13;
    v86.eax = 0x800;
    v86.edx = bd->bd_unit;
    v86int();
    
    if (!(v86.efl & PSL_C) &&                           /* carry clear */
        ((v86.edx & 0xff) > ((unsigned)bd->bd_unit & 0x7f))) {  /* unit # OK */

        /*
         * Ignore devices with an absurd sector size.
         */
        if ((v86.ecx & 0x3f) == 0) {
                DEBUG("Invalid geometry for unit %d", bd->bd_unit);
                return(0);
        }
        bd->bd_flags |= BD_MODEINT13;
        bd->bd_type = v86.ebx & 0xff;

        /* Determine if we can use EDD with this device. */
        v86.ctl = V86_FLAGS;
        v86.addr = 0x13;
        v86.eax = 0x4100;
        v86.edx = bd->bd_unit;
        v86.ebx = 0x55aa;
        v86int();
        if (!(v86.efl & PSL_C) &&                       /* carry clear */
            ((v86.ebx & 0xffff) == 0xaa55) &&           /* signature */
            (v86.ecx & 0x1)) {                          /* packets mode ok */
            bd->bd_flags |= BD_MODEEDD1;
            if((v86.eax & 0xff00) > 0x300)
                bd->bd_flags |= BD_MODEEDD3;
        }
        return(1);
    }
    return(0);
}

/*
 * Print information about disks
 */
static void
bd_print(int verbose)
{
    int                         i, j;
    char                        line[80];
    struct i386_devdesc         dev;
    struct open_disk            *od;
    struct dos_partition        *dptr;
    
    for (i = 0; i < nbdinfo; i++) {
        sprintf(line, "    disk%d:   BIOS drive %c:\n", i, 
                (bdinfo[i].bd_unit < 0x80) ? ('A' + bdinfo[i].bd_unit) : ('C' + bdinfo[i].bd_unit - 0x80));
        pager_output(line);

        /* try to open the whole disk */
        dev.d_kind.biosdisk.unit = i;
        dev.d_kind.biosdisk.slice = -1;
        dev.d_kind.biosdisk.partition = -1;
        
        if (!bd_opendisk(&od, &dev)) {

            /* Do we have a partition table? */
            if (od->od_flags & BD_PARTTABOK) {
                dptr = &od->od_slicetab[0];

                /* Check for a "dedicated" disk */
                if ((dptr[3].dp_typ == DOSPTYP_386BSD ||
                     dptr[3].dp_typ == DOSPTYP_NETBSD ||
                     dptr[3].dp_typ == DOSPTYP_DFLYBSD) &&
                    (dptr[3].dp_start == 0) &&
                    (dptr[3].dp_size == 50000)) {
                    sprintf(line, "      disk%d", i);
                    bd_printbsdslice(od, 0, line, verbose);
                } else {
                    for (j = 0; j < od->od_nslices; j++) {
                        sprintf(line, "      disk%ds%d", i, j + 1);
                        bd_printslice(od, &dptr[j], line, verbose);
                    }
                }
            }
            bd_closedisk(od);
        }
    }
}

/*
 * Print information about slices on a disk.  For the size calculations we
 * assume a 512 byte sector.
 */
static void
bd_printslice(struct open_disk *od, struct dos_partition *dp, char *prefix,
        int verbose)
{
        char line[80];

        switch (dp->dp_typ) {
        case DOSPTYP_DFLYBSD:
        case DOSPTYP_386BSD:
        case DOSPTYP_NETBSD:
        /* XXX: possibly add types 0 and 1, as in subr_disk, for gpt magic */
                bd_printbsdslice(od, (daddr_t)dp->dp_start, prefix, verbose);
                return;
        case DOSPTYP_LINSWP:
                if (verbose)
                        sprintf(line, "%s: Linux swap %.6dMB (%d - %d)\n",
                            prefix, dp->dp_size / 2048,
                            dp->dp_start, dp->dp_start + dp->dp_size);
                else
                        sprintf(line, "%s: Linux swap\n", prefix);
                break;
        case DOSPTYP_LINUX:
                /*
                 * XXX
                 * read the superblock to confirm this is an ext2fs partition?
                 */
                if (verbose)
                        sprintf(line, "%s: ext2fs  %.6dMB (%d - %d)\n", prefix,
                            dp->dp_size / 2048, dp->dp_start,
                            dp->dp_start + dp->dp_size);
                else
                        sprintf(line, "%s: ext2fs\n", prefix);
                break;
        case 0x00:                              /* unused partition */
        case DOSPTYP_EXT:
                return;
        case 0x01:
                if (verbose)
                        sprintf(line, "%s: FAT-12  %.6dMB (%d - %d)\n", prefix,
                            dp->dp_size / 2048, dp->dp_start,
                            dp->dp_start + dp->dp_size);
                else
                        sprintf(line, "%s: FAT-12\n", prefix);
                break;
        case 0x04:
        case 0x06:
        case 0x0e:
                if (verbose)
                        sprintf(line, "%s: FAT-16  %.6dMB (%d - %d)\n", prefix,
                            dp->dp_size / 2048, dp->dp_start,
                            dp->dp_start + dp->dp_size);
                else
                        sprintf(line, "%s: FAT-16\n", prefix);
                break;
        case 0x0b:
        case 0x0c:
                if (verbose)
                        sprintf(line, "%s: FAT-32  %.6dMB (%d - %d)\n", prefix,
                            dp->dp_size / 2048, dp->dp_start,
                            dp->dp_start + dp->dp_size);
                else
                        sprintf(line, "%s: FAT-32\n", prefix);
                break;
        default:
                if (verbose)
                        sprintf(line, "%s: Unknown fs: 0x%x  %.6dMB (%d - %d)\n",
                            prefix, dp->dp_typ, dp->dp_size / 2048,
                            dp->dp_start, dp->dp_start + dp->dp_size);
                else
                        sprintf(line, "%s: Unknown fs: 0x%x\n", prefix,
                            dp->dp_typ);
        }
        pager_output(line);
}

static void
print_partition(u_int8_t fstype, unsigned long long offset,
                unsigned long long size, int i, int od_flags,
                char *prefix, int verbose, int type)
{
        char    line[80];

        /*
         * For each partition, make sure we know what type of fs it is.  If
         * not, then skip it.  However, since floppies often have bogus
         * fstypes, print the 'a' partition on a floppy even if it is marked
         * unused.
         */
        if ((fstype == FS_SWAP) ||
            (fstype == FS_VINUM) ||
            (fstype == FS_HAMMER) ||
            (fstype == FS_HAMMER2) ||
            (fstype == FS_BSDFFS) ||
            (fstype == FS_ZFS) ||
            (fstype == FS_JFS2) ||
            ((fstype == FS_UNUSED) &&
             (od_flags & BD_FLOPPY) && (i == 0))) {

                /* Only print out statistics in verbose mode */
                if (verbose) {
                        sprintf(line, "%c %s%c: %s  %.6lluMB (%llu - %llu)\n",
                            /* prefix disks that can be used to load modules with '*' */
                            ((fstype == FS_BSDFFS) || (fstype == FS_UNUSED) ||
                            (fstype == FS_VINUM)) ? '*' : ' ',
                            prefix, 'a' + i,
                            (fstype == FS_SWAP) ? "swap" :
                            (fstype == FS_VINUM) ? "vinum" :
                            (fstype == FS_HAMMER) ? "HAMMER" :
                            (fstype == FS_HAMMER2) ? "HAMMER2" :
                            (fstype == FS_JFS2) ? "JFS2" :
                            (fstype == FS_ZFS) ? "ZFS" :
                            (fstype == FS_BSDFFS) ? "FFS" :
                            "(unknown)",
                            (type==32)?(size / 2048):(size/1024/1024),
                            offset,
                            offset + size);
                } else {
                        sprintf(line, "%c %s%c: %s\n",
                            /* prefix disks that can be used to load modules with '*' */
                            ((fstype == FS_BSDFFS) || (fstype == FS_UNUSED) ||
                            (fstype == FS_VINUM)) ? '*' : ' ',
                            prefix, 'a' + i,
                            (fstype == FS_SWAP) ? "swap" :
                            (fstype == FS_VINUM) ? "vinum" :
                            (fstype == FS_HAMMER) ? "HAMMER" :
                            (fstype == FS_HAMMER2) ? "HAMMER2" :
                            (fstype == FS_JFS2) ? "JFS2" :
                            (fstype == FS_ZFS) ? "ZFS" :
                            (fstype == FS_BSDFFS) ? "FFS" :
                            "(unknown)");
                }

                pager_output(line);
        }
}

/*
 * Print out each valid partition in the disklabel of a FreeBSD slice.
 * For size calculations, we assume a 512 byte sector size.
 */
static void
bd_printbsdslice(struct open_disk *od, daddr_t offset, char *prefix,
    int verbose)
{
        char            line[80];
        char            buf[BIOSDISK_SECSIZE*2];
        struct disklabel32      *lp = NULL;
        struct disklabel64      *lp64 = NULL;
        int                     i;

        /* read disklabel */
        if (bd_read(od, offset + LABELSECTOR32, 1, buf))
                return;
        lp =(struct disklabel32 *)(&buf[0]);
        if (lp->d_magic != DISKMAGIC32) {
                if (bd_read(od, offset, 2, buf))
                        return;

                lp64 =(struct disklabel64 *)(&buf[0]);
                if (lp64->d_magic != DISKMAGIC64) {
                        sprintf(line, "%s: bad disklabel\n", prefix);
                        pager_output(line);
                        return;
                }
                lp = NULL; /* PARANOID */
        }
        if (lp64) {
                /* We got ourselves a disklabel64 here */
                for (i = 0; i < lp64->d_npartitions; i++) {
                        if (lp64->d_partitions[i].p_bsize == 0)
                                continue;

                        print_partition(lp64->d_partitions[i].p_fstype,
                                        lp64->d_partitions[i].p_boffset,
                                        lp64->d_partitions[i].p_bsize,
                                        i, od->od_flags, prefix, verbose, 64);
                }
        } else if (lp) {
                /* Print partitions */
                for (i = 0; i < lp->d_npartitions; i++) {
                        print_partition(lp->d_partitions[i].p_fstype,
                                        lp->d_partitions[i].p_offset,
                                        lp->d_partitions[i].p_size,
                                        i, od->od_flags, prefix, verbose, 32);
                }
        }
}


/*
 * Attempt to open the disk described by (dev) for use by (f).
 *
 * Note that the philosophy here is "give them exactly what
 * they ask for".  This is necessary because being too "smart"
 * about what the user might want leads to complications.
 * (eg. given no slice or partition value, with a disk that is
 *  sliced - are they after the first BSD slice, or the DOS
 *  slice before it?)
 */
static int 
bd_open(struct open_file *f, ...)
{
    va_list                     ap;
    struct i386_devdesc         *dev;
    struct open_disk            *od;
    int                         error;

    va_start(ap, f);
    dev = va_arg(ap, struct i386_devdesc *);
    va_end(ap);
    if ((error = bd_opendisk(&od, dev)))
        return(error);
    
    /*
     * Save our context
     */
    ((struct i386_devdesc *)(f->f_devdata))->d_kind.biosdisk.data = od;
    DEBUG("open_disk %p, partition at 0x%x", od, od->od_boff);
    return(0);
}

static int
bd_opendisk(struct open_disk **odp, struct i386_devdesc *dev)
{
    struct dos_partition        *dptr;
    struct disklabel32          *lp;
    struct disklabel64          *lp64;
    struct open_disk            *od;
    int                         sector, slice, i;
    int                         error;
    static char                 buf[BUFSIZE];

    if (dev->d_kind.biosdisk.unit >= nbdinfo) {
        DEBUG("attempt to open nonexistent disk");
        return(ENXIO);
    }
    
    od = (struct open_disk *)malloc(sizeof(struct open_disk));
    if (!od) {
        DEBUG("no memory");
        return (ENOMEM);
    }

    /* Look up BIOS unit number, intialise open_disk structure */
    od->od_dkunit = dev->d_kind.biosdisk.unit;
    od->od_unit = bdinfo[od->od_dkunit].bd_unit;
    od->od_flags = bdinfo[od->od_dkunit].bd_flags;
    od->od_boff = 0;
    od->od_nslices = 0;
    error = 0;
    DEBUG("open '%s', unit 0x%x slice %d partition %c",
             i386_fmtdev(dev), dev->d_kind.biosdisk.unit, 
             dev->d_kind.biosdisk.slice, dev->d_kind.biosdisk.partition + 'a');

    /* Get geometry for this open (removable device may have changed) */
    if (bd_getgeom(od)) {
        DEBUG("can't get geometry");
        error = ENXIO;
        goto out;
    }

    /*
     * Following calculations attempt to determine the correct value
     * for d->od_boff by looking for the slice and partition specified,
     * or searching for reasonable defaults.
     */

    /*
     * Find the slice in the DOS slice table.
     */
    if (bd_read(od, 0, 1, buf)) {
        DEBUG("error reading MBR");
        error = EIO;
        goto out;
    }

    /* 
     * Check the slice table magic.
     */
    if (((u_char)buf[0x1fe] != 0x55) || ((u_char)buf[0x1ff] != 0xaa)) {
        /* If a slice number was explicitly supplied, this is an error */
        if (dev->d_kind.biosdisk.slice > 0) {
            DEBUG("no slice table/MBR (no magic)");
            error = ENOENT;
            goto out;
        }
        sector = 0;
        goto unsliced;          /* may be a floppy */
    }

    /*
     * copy the partition table, then pick up any extended partitions.  The
     * base partition table always has four entries, even if some of them
     * represented extended partitions.  However, any additional sub-extended
     * partitions will be silently recursed and not included in the slice
     * table.
     */
    bcopy(buf + DOSPARTOFF, &od->od_slicetab,
      sizeof(struct dos_partition) * NDOSPART);
    od->od_nslices = NDOSPART;

    dptr = &od->od_slicetab[0];
    for (i = 0; i < NDOSPART; i++, dptr++) {
        if ((dptr->dp_typ == DOSPTYP_EXT) || (dptr->dp_typ == DOSPTYP_EXTLBA))
            bd_chainextended(od, dptr->dp_start, 0); /* 1st offset is zero */
    }
    od->od_flags |= BD_PARTTABOK;
    dptr = &od->od_slicetab[0];

    /*
     * Overflow entries are not loaded into memory but we still keep
     * track of the count.  Fix it up now.
     */
    if (od->od_nslices > NEXTDOSPART)
        od->od_nslices = NEXTDOSPART;

    /* 
     * Is this a request for the whole disk? 
     */
    if (dev->d_kind.biosdisk.slice == -1) {
        sector = 0;
        goto unsliced;
    }

    /*
     * if a slice number was supplied but not found, this is an error.
     */
    if (dev->d_kind.biosdisk.slice > 0) {
        slice = dev->d_kind.biosdisk.slice - 1;
        if (slice >= od->od_nslices) {
            DEBUG("slice %d not found", slice);
            error = ENOENT;
            goto out;
        }
    }

    /*
     * Check for the historically bogus MBR found on true dedicated disks
     */
    if ((dptr[3].dp_typ == DOSPTYP_386BSD ||
         dptr[3].dp_typ == DOSPTYP_DFLYBSD) &&
      (dptr[3].dp_start == 0) &&
      (dptr[3].dp_size == 50000)) {
        sector = 0;
        goto unsliced;
    }

    /* Try to auto-detect the best slice; this should always give a slice number */
    if (dev->d_kind.biosdisk.slice == 0) {
        slice = bd_bestslice(od);
        if (slice == -1) {
            error = ENOENT;
            goto out;
        }
        dev->d_kind.biosdisk.slice = slice;
    }

    dptr = &od->od_slicetab[0];
    /*
     * Accept the supplied slice number unequivocally (we may be looking
     * at a DOS partition).
     */
    dptr += (dev->d_kind.biosdisk.slice - 1);   /* we number 1-4, offsets are 0-3 */
    sector = dptr->dp_start;
    DEBUG("slice entry %d at %d, %d sectors", dev->d_kind.biosdisk.slice - 1, sector, dptr->dp_size);

    /*
     * If we are looking at a BSD slice, and the partition is < 0,
     * assume the 'a' partition
     */
    if ((dptr->dp_typ == DOSPTYP_386BSD ||
         dptr->dp_typ == DOSPTYP_DFLYBSD) &&
        dev->d_kind.biosdisk.partition < 0) {
        dev->d_kind.biosdisk.partition = 0;
    }

unsliced:
    /* 
     * Now we have the slice offset, look for the partition in the disklabel if we have
     * a partition to start with.
     *
     * XXX we might want to check the label checksum.
     */
    if (dev->d_kind.biosdisk.partition < 0) {
        od->od_boff = sector;           /* no partition, must be after the slice */
        DEBUG("opening raw slice");
    } else {
        
        if (bd_read(od, sector + LABELSECTOR32, 1, buf)) {
            DEBUG("error reading disklabel");
            error = EIO;
            goto out;
        }
        DEBUG("copy %d bytes of label from %p to %p", sizeof(struct disklabel32), buf + LABELOFFSET32, &od->od_disklabel);
        bcopy(buf + LABELOFFSET32, &od->od_disklabel, sizeof(struct disklabel32));
        lp = &od->od_disklabel;

        if (lp->d_magic == DISKMAGIC32) {
            od->od_flags |= BD_LABELOK;

            if (dev->d_kind.biosdisk.partition >= lp->d_npartitions) {
                DEBUG("partition '%c' exceeds partitions in table (a-'%c')",
                      'a' + dev->d_kind.biosdisk.partition, 'a' + lp->d_npartitions);
                error = EPART;
                goto out;

            }

#ifdef DISK_DEBUG
            /* Complain if the partition is unused unless this is a floppy. */
            if ((lp->d_partitions[dev->d_kind.biosdisk.partition].p_fstype == FS_UNUSED) &&
                !(od->od_flags & BD_FLOPPY))
                DEBUG("warning, partition marked as unused");
#endif
            
            od->od_boff = 
                    lp->d_partitions[dev->d_kind.biosdisk.partition].p_offset -
                    lp->d_partitions[RAW_PART].p_offset +
                    sector;

            goto out;
        }

        /* else maybe DISKLABEL64? */

        if (bd_read(od, sector, (sizeof(od->od_disklabel64) + 511) / 512, buf)) {
            DEBUG("error reading disklabel");
            error = EIO;
            goto out;
        }
        DEBUG("copy %d bytes of label from %p to %p", sizeof(od->od_disklabel64), buf, &od->od_disklabel64);
        bcopy(buf, &od->od_disklabel64, sizeof(od->od_disklabel64));
        lp64 = &od->od_disklabel64;

        if (lp64->d_magic == DISKMAGIC64) {
            od->od_flags |= BD_LABELOK;

            if (dev->d_kind.biosdisk.partition >= lp64->d_npartitions ||
                lp64->d_partitions[dev->d_kind.biosdisk.partition].p_bsize == 0) {
                DEBUG("partition '%c' exceeds partitions in table (a-'%c')",
                      'a' + dev->d_kind.biosdisk.partition, 'a' + lp64->d_npartitions);
                error = EPART;
                goto out;

            }

            od->od_boff = 
                    lp64->d_partitions[dev->d_kind.biosdisk.partition].p_boffset / 512 +
                    sector;

            DEBUG("disklabel64 slice at %d", od->od_boff);

        } else {
            DEBUG("no disklabel");
            error = ENOENT;
        }
    }

 out:
    if (error) {
        free(od);
    } else {
        *odp = od;      /* return the open disk */
    }
    return(error);
}


static void
bd_chainextended(struct open_disk *od, u_int32_t base, u_int32_t offset)
{
        char   buf[BIOSDISK_SECSIZE];
        struct dos_partition *dp1, *dp2;
        int i;

        if (bd_read(od, (daddr_t)(base + offset), 1, buf)) {
                printf("\nerror reading extended partition table");
                return;
        }

        /*
         * dp1 points to the first record in the on-disk XPT,
         * dp2 points to the next entry in the in-memory parition table.
         *
         * NOTE: dp2 may be out of bounds if od_nslices >= NEXTDOSPART.
         *
         * NOTE: unlike the extended partitions in our primary dos partition
         * table, we do not record recursed extended partitions themselves 
         * in our in-memory partition table.
         *
         * NOTE: recording within our in-memory table must be breadth first
         * ot match what the kernel does.  Thus, two passes are required.
         *
         * NOTE: partitioning programs which support extended partitions seem
         * to always use the first entry for the user partition and the
         * second entry to chain, and also appear to disallow more then one
         * extended partition at each level.  Nevertheless we make our code
         * somewhat more generic (and the same as the kernel's own slice
         * scan).
         */
        dp1 = (struct dos_partition *)(&buf[DOSPARTOFF]);
        dp2 = &od->od_slicetab[od->od_nslices];

        for (i = 0; i < NDOSPART; ++i, ++dp1) {
                if (dp1->dp_scyl == 0 && dp1->dp_shd == 0 &&
                    dp1->dp_ssect == 0 && dp1->dp_start == 0 && 
                    dp1->dp_size == 0) {
                        continue;
                }
                if ((dp1->dp_typ == DOSPTYP_EXT) || 
                    (dp1->dp_typ == DOSPTYP_EXTLBA)) {
                        /*
                         * breadth first traversal, must skip in the 
                         * first pass
                         */
                        continue;
                }

                /*
                 * Only load up the in-memory data if we haven't overflowed
                 * our in-memory array.
                 */
                if (od->od_nslices < NEXTDOSPART) {
                        dp2->dp_typ = dp1->dp_typ;
                        dp2->dp_start = base + offset + dp1->dp_start;
                        dp2->dp_size = dp1->dp_size;
                }
                ++od->od_nslices;
                ++dp2;
        }

        /*
         * Pass 2 - handle extended partitions.  Note that the extended
         * slice itself is not stored in the slice array when we recurse,
         * but any 'original' top-level extended slices are.  This is to
         * match what the kernel does.
         */
        dp1 -= NDOSPART;
        for (i = 0; i < NDOSPART; ++i, ++dp1) {
                if (dp1->dp_scyl == 0 && dp1->dp_shd == 0 &&
                    dp1->dp_ssect == 0 && dp1->dp_start == 0 && 
                    dp1->dp_size == 0) {
                        continue;
                }
                if ((dp1->dp_typ == DOSPTYP_EXT) || 
                    (dp1->dp_typ == DOSPTYP_EXTLBA))
                        bd_chainextended(od, base, dp1->dp_start);
        }
}

/*
 * Search for a slice with the following preferences:
 *
 * 1: Active FreeBSD slice
 * 2: Non-active FreeBSD slice
 * 3: Active Linux slice
 * 4: non-active Linux slice
 * 5: Active FAT/FAT32 slice
 * 6: non-active FAT/FAT32 slice
 */
#define PREF_RAWDISK    0
#define PREF_FBSD_ACT   1
#define PREF_FBSD       2
#define PREF_LINUX_ACT  3
#define PREF_LINUX      4
#define PREF_DOS_ACT    5
#define PREF_DOS        6
#define PREF_NONE       7

/*
 * slicelimit is in the range 0 .. NDOSPART
 */
static int
bd_bestslice(struct open_disk *od)
{
        struct dos_partition *dp;
        int pref, preflevel;
        int i, prefslice;
        
        prefslice = 0;
        preflevel = PREF_NONE;

        dp = &od->od_slicetab[0];
        for (i = 0; i < od->od_nslices; i++, dp++) {
                switch (dp->dp_typ) {
                case DOSPTYP_DFLYBSD:           /* DragonFlyBSD */
                case DOSPTYP_386BSD:            /* FreeBSD and old DFlyBSD */
                        pref = dp->dp_flag & 0x80 ? PREF_FBSD_ACT : PREF_FBSD;
                        break;

                case DOSPTYP_LINUX:
                        pref = dp->dp_flag & 0x80 ? PREF_LINUX_ACT : PREF_LINUX;
                        break;
    
                case 0x01:              /* DOS/Windows */
                case 0x04:
                case 0x06:
                case 0x0b:
                case 0x0c:
                case 0x0e:
                        pref = dp->dp_flag & 0x80 ? PREF_DOS_ACT : PREF_DOS;
                        break;

                default:
                        pref = PREF_NONE;
                }
                if (pref < preflevel) {
                        preflevel = pref;
                        prefslice = i + 1;
                }
        }
        return (prefslice);
}
 
static int 
bd_close(struct open_file *f)
{
    struct open_disk    *od = (struct open_disk *)(((struct i386_devdesc *)(f->f_devdata))->d_kind.biosdisk.data);

    bd_closedisk(od);
    return(0);
}

static void
bd_closedisk(struct open_disk *od)
{
    DEBUG("open_disk %p", od);
#if 0
    /* XXX is this required? (especially if disk already open...) */
    if (od->od_flags & BD_FLOPPY)
        delay(3000000);
#endif
    free(od);
}

static int 
bd_strategy(void *devdata, int rw, daddr_t dblk, size_t size, char *buf, size_t *rsize)
{
    struct bcache_devdata       bcd;
    struct open_disk    *od = (struct open_disk *)(((struct i386_devdesc *)devdata)->d_kind.biosdisk.data);

    bcd.dv_strategy = bd_realstrategy;
    bcd.dv_devdata = devdata;
    return(bcache_strategy(&bcd, od->od_unit, rw, dblk+od->od_boff, size, buf, rsize));
}

static int 
bd_realstrategy(void *devdata, int rw, daddr_t dblk, size_t size, char *buf, size_t *rsize)
{
    struct open_disk    *od = (struct open_disk *)(((struct i386_devdesc *)devdata)->d_kind.biosdisk.data);
    int                 blks;
#ifdef BD_SUPPORT_FRAGS
    char                fragbuf[BIOSDISK_SECSIZE];
    size_t              fragsize;

    fragsize = size % BIOSDISK_SECSIZE;
#else
    if (size % BIOSDISK_SECSIZE)
        panic("bd_strategy: %d bytes I/O not multiple of block size", size);
#endif

    DEBUG("open_disk %p", od);

    switch(rw){
    case F_READ:
        blks = size / BIOSDISK_SECSIZE;
        DEBUG("read %d from %d to %p", blks, dblk, buf);

        if (rsize)
            *rsize = 0;
        if (blks && bd_read(od, dblk, blks, buf)) {
            DEBUG("read error");
            return (EIO);
        }
#ifdef BD_SUPPORT_FRAGS
        DEBUG("bd_strategy: frag read %d from %d+%d to %p", 
             fragsize, dblk, blks, buf + (blks * BIOSDISK_SECSIZE));
        if (fragsize && bd_read(od, dblk + blks, 1, fragsize)) {
            DEBUG("frag read error");
            return(EIO);
        }
        bcopy(fragbuf, buf + (blks * BIOSDISK_SECSIZE), fragsize);
#endif
        if (rsize)
            *rsize = size;
        return (0);
    case F_WRITE :
        blks = size / BIOSDISK_SECSIZE;
        DEBUG("write %d from %d to %p", blks, dblk, buf);

        if (rsize)
            *rsize = 0;
        if (blks && bd_write(od, dblk, blks, buf)) {
            DEBUG("write error");
            return (EIO);
        }
#ifdef BD_SUPPORT_FRAGS
        if(fragsize) {
            DEBUG("Attempted to write a frag");
            return (EIO);
        }
#endif
        if (rsize)
            *rsize = size;
        return (0);
    default:
        break; /* DO NOTHING */
    }
    return EROFS;
}

static int
bd_read(struct open_disk *od, daddr_t dblk, int blks, caddr_t dest)
{
    u_int       x, bpc, cyl, hd, sec, result, resid, retry, maxfer;
    caddr_t     p, xp, bbuf, breg;
    
    /* Just in case some idiot actually tries to read -1 blocks... */
    if (blks < 0)
        return (-1);

    bpc = (od->od_sec * od->od_hds);            /* blocks per cylinder */
    resid = blks;
    p = dest;

    /*
     * Always bounce.  Our buffer is probably not segment-addressable.
     */
    if (1) {
        /* 
         * There is a 64k physical boundary somewhere in the destination
         * buffer, so we have to arrange a suitable bounce buffer.  Allocate
         * a buffer twice as large as we need to.  Use the bottom half unless
         * there is a break there, in which case we use the top half.
         */
        bbuf = bounce_base;
        x = min(BOUNCEBUF_SECTS / 2, (unsigned)blks);

        if (((u_int32_t)VTOP(bbuf) & 0xffff8000) ==
            ((u_int32_t)VTOP(bbuf + x * BIOSDISK_SECSIZE - 1) & 0xffff8000)) {
            breg = bbuf;
        } else {
            breg = bbuf + x * BIOSDISK_SECSIZE;
        }
        maxfer = x;             /* limit transfers to bounce region size */
    } else {
        breg = bbuf = NULL;
        maxfer = 0;
    }
    
    while (resid > 0) {
        x = dblk;
        cyl = x / bpc;                  /* block # / blocks per cylinder */
        x %= bpc;                       /* block offset into cylinder */
        hd = x / od->od_sec;            /* offset / blocks per track */
        sec = x % od->od_sec;           /* offset into track */

        /* play it safe and don't cross track boundaries (XXX this is probably unnecessary) */
        x = szmin(od->od_sec - sec, resid);
        if (maxfer > 0)
            x = min(x, maxfer);         /* fit bounce buffer */

        /* where do we transfer to? */
        xp = (bbuf == NULL ? p : breg);

        /* correct sector number for 1-based BIOS numbering */
        sec++;

        /*
         * Loop retrying the operation a couple of times.  The BIOS may also
         * retry.
         */
        for (retry = 0; retry < 3; retry++) {
            /*
             * If retrying, reset the drive.
             */
            if (retry > 0) {
                v86.ctl = V86_FLAGS;
                v86.addr = 0x13;
                v86.eax = 0;
                v86.edx = od->od_unit;
                v86int();
            }
            
            /*
             * Always use EDD if the disk supports it, otherwise fall back
             * to CHS mode (returning an error if the cylinder number is
             * too large).
             */
            if (od->od_flags & BD_MODEEDD1) {
                static unsigned short packet[8];

                packet[0] = 0x10;
                packet[1] = x;
                packet[2] = VTOPOFF(xp);
                packet[3] = VTOPSEG(xp);
                packet[4] = dblk & 0xffff;
                packet[5] = dblk >> 16;
                packet[6] = 0;
                packet[7] = 0;
                v86.ctl = V86_FLAGS;
                v86.addr = 0x13;
                v86.eax = 0x4200;
                v86.edx = od->od_unit;
                v86.ds = VTOPSEG(packet);
                v86.esi = VTOPOFF(packet);
                v86int();
                result = (v86.efl & PSL_C);
                if (result == 0)
                    break;
            } else if (cyl < 1024) {
                /* Use normal CHS addressing */
                v86.ctl = V86_FLAGS;
                v86.addr = 0x13;
                v86.eax = 0x200 | x;
                v86.ecx = ((cyl & 0xff) << 8) | ((cyl & 0x300) >> 2) | sec;
                v86.edx = (hd << 8) | od->od_unit;
                v86.es = VTOPSEG(xp);
                v86.ebx = VTOPOFF(xp);
                v86int();
                result = (v86.efl & PSL_C);
                if (result == 0)
                    break;
            } else {
                result = 1;
                break;
            }
        }
        
        DEBUG("%u sectors from %u/%u/%d to %p (0x%x) %s",
              x, cyl, hd, sec - 1, p, VTOP(p), result ? "failed" : "ok");
        /* BUG here, cannot use v86 in printf because putchar uses it too */
        DEBUG("ax = 0x%04x cx = 0x%04x dx = 0x%04x status 0x%x", 
              0x200 | x,
              ((cyl & 0xff) << 8) | ((cyl & 0x300) >> 2) | sec,
              (hd << 8) | od->od_unit,
              (v86.eax >> 8) & 0xff);
        if (result)
            return(-1);
        if (bbuf != NULL)
            bcopy(breg, p, x * BIOSDISK_SECSIZE);
        p += (x * BIOSDISK_SECSIZE);
        dblk += x;
        resid -= x;
    }
        
/*    hexdump(dest, (blks * BIOSDISK_SECSIZE)); */
    return(0);
}


static int
bd_write(struct open_disk *od, daddr_t dblk, int blks, caddr_t dest)
{
    u_int       x, bpc, cyl, hd, sec, result, resid, retry, maxfer;
    caddr_t     p, xp, bbuf, breg;
    
    /* Just in case some idiot actually tries to read -1 blocks... */
    if (blks < 0)
        return (-1);

    bpc = (od->od_sec * od->od_hds);            /* blocks per cylinder */
    resid = blks;
    p = dest;

    /*
     * Always bounce.  Our buffer is probably not segment-addressable.
     */
    if (1) {
        /* 
         * There is a 64k physical boundary somewhere in the destination
         * buffer, so we have to arrange a suitable bounce buffer.  Allocate
         * a buffer twice as large as we need to.  Use the bottom half
         * unless there is a break there, in which case we use the top half.
         */
        bbuf = bounce_base;
        x = min(BOUNCEBUF_SECTS / 2, (unsigned)blks);

        if (((u_int32_t)VTOP(bbuf) & 0xffff8000) ==
            ((u_int32_t)VTOP(bbuf + x * BIOSDISK_SECSIZE - 1) & 0xffff8000)) {
            breg = bbuf;
        } else {
            breg = bbuf + x * BIOSDISK_SECSIZE;
        }
        maxfer = x;             /* limit transfers to bounce region size */
    } else {
        breg = bbuf = NULL;
        maxfer = 0;
    }

    while (resid > 0) {
        x = dblk;
        cyl = x / bpc;                  /* block # / blocks per cylinder */
        x %= bpc;                       /* block offset into cylinder */
        hd = x / od->od_sec;            /* offset / blocks per track */
        sec = x % od->od_sec;           /* offset into track */

        /* play it safe and don't cross track boundaries (XXX this is probably unnecessary) */
        x = szmin(od->od_sec - sec, resid);
        if (maxfer > 0)
            x = szmin(x, maxfer);               /* fit bounce buffer */

        /* where do we transfer to? */
        xp = (bbuf == NULL ? p : breg);

        /* correct sector number for 1-based BIOS numbering */
        sec++;


        /* Put your Data In, Put your Data out,
           Put your Data In, and shake it all about 
        */
        if (bbuf != NULL)
            bcopy(p, breg, x * BIOSDISK_SECSIZE);
        p += (x * BIOSDISK_SECSIZE);
        dblk += x;
        resid -= x;

        /*
         * Loop retrying the operation a couple of times.  The BIOS may also
         * retry.
         */
        for (retry = 0; retry < 3; retry++) {
            /*
             * If retrying, reset the drive.
             */
            if (retry > 0) {
                v86.ctl = V86_FLAGS;
                v86.addr = 0x13;
                v86.eax = 0;
                v86.edx = od->od_unit;
                v86int();
            }

            /*
             * Always use EDD if the disk supports it, otherwise fall back
             * to CHS mode (returning an error if the cylinder number is
             * too large).
             */
            if (od->od_flags & BD_MODEEDD1) {
                static unsigned short packet[8];

                packet[0] = 0x10;
                packet[1] = x;
                packet[2] = VTOPOFF(xp);
                packet[3] = VTOPSEG(xp);
                packet[4] = dblk & 0xffff;
                packet[5] = dblk >> 16;
                packet[6] = 0;
                packet[7] = 0;
                v86.ctl = V86_FLAGS;
                v86.addr = 0x13;
                    /* Should we Write with verify ?? 0x4302 ? */
                v86.eax = 0x4300;
                v86.edx = od->od_unit;
                v86.ds = VTOPSEG(packet);
                v86.esi = VTOPOFF(packet);
                v86int();
                result = (v86.efl & PSL_C);
                if (result == 0)
                    break;
            } else if (cyl < 1024) {
                /* Use normal CHS addressing */
                v86.ctl = V86_FLAGS;
                v86.addr = 0x13;
                v86.eax = 0x300 | x;
                v86.ecx = ((cyl & 0xff) << 8) | ((cyl & 0x300) >> 2) | sec;
                v86.edx = (hd << 8) | od->od_unit;
                v86.es = VTOPSEG(xp);
                v86.ebx = VTOPOFF(xp);
                v86int();
                result = (v86.efl & PSL_C);
                if (result == 0)
                    break;
            } else {
                result = 1;
                break;
            }
        }
        
        DEBUG("%u sectors from %u/%u/%d to %p (0x%x) %s", x, cyl, hd, sec - 1, p, VTOP(p), result ? "failed" : "ok");
        /* BUG here, cannot use v86 in printf because putchar uses it too */
        DEBUG("ax = 0x%04x cx = 0x%04x dx = 0x%04x status 0x%x", 
              0x200 | x, ((cyl & 0xff) << 8) | ((cyl & 0x300) >> 2) | sec, (hd << 8) | od->od_unit, (v86.eax >> 8) & 0xff);
        if (result)
            return(-1);
    }
        
    /* hexdump(dest, (blks * BIOSDISK_SECSIZE)); */
    return(0);
}
static int
bd_getgeom(struct open_disk *od)
{

    v86.ctl = V86_FLAGS;
    v86.addr = 0x13;
    v86.eax = 0x800;
    v86.edx = od->od_unit;
    v86int();

    if ((v86.efl & PSL_C) ||                            /* carry set */
        ((v86.edx & 0xff) <= (unsigned)(od->od_unit & 0x7f)))   /* unit # bad */
        return(1);
    
    /* convert max cyl # -> # of cylinders */
    od->od_cyl = ((v86.ecx & 0xc0) << 2) + ((v86.ecx & 0xff00) >> 8) + 1;
    /* convert max head # -> # of heads */
    od->od_hds = ((v86.edx & 0xff00) >> 8) + 1;
    od->od_sec = v86.ecx & 0x3f;

    DEBUG("unit 0x%x geometry %d/%d/%d", od->od_unit, od->od_cyl, od->od_hds, od->od_sec);
    return(0);
}

/*
 * Return the BIOS geometry of a given "fixed drive" in a format
 * suitable for the legacy bootinfo structure.  Since the kernel is
 * expecting raw int 0x13/0x8 values for N_BIOS_GEOM drives, we
 * prefer to get the information directly, rather than rely on being
 * able to put it together from information already maintained for
 * different purposes and for a probably different number of drives.
 *
 * For valid drives, the geometry is expected in the format (31..0)
 * "000000cc cccccccc hhhhhhhh 00ssssss"; and invalid drives are
 * indicated by returning the geometry of a "1.2M" PC-format floppy
 * disk.  And, incidentally, what is returned is not the geometry as
 * such but the highest valid cylinder, head, and sector numbers.
 */
u_int32_t
bd_getbigeom(int bunit)
{

    v86.ctl = V86_FLAGS;
    v86.addr = 0x13;
    v86.eax = 0x800;
    v86.edx = 0x80 + bunit;
    v86int();
    if (v86.efl & PSL_C)
        return 0x4f010f;
    return ((v86.ecx & 0xc0) << 18) | ((v86.ecx & 0xff00) << 8) |
           (v86.edx & 0xff00) | (v86.ecx & 0x3f);
}

/*
 * Return a suitable cdev_t value for (dev).
 *
 * In the case where it looks like (dev) is a SCSI disk, we allow the number of
 * IDE disks to be specified in $num_ide_disks.  There should be a Better Way.
 */
int
bd_getdev(struct i386_devdesc *dev)
{
    struct open_disk            *od;
    int                         biosdev;
    int                         major;
    int                         rootdev;
    char                        *nip, *cp;
    int                         unitofs = 0, i, unit;

    biosdev = bd_unit2bios(dev->d_kind.biosdisk.unit);
    DEBUG("unit %d BIOS device %d", dev->d_kind.biosdisk.unit, biosdev);
    if (biosdev == -1)                          /* not a BIOS device */
        return(-1);
    if (bd_opendisk(&od, dev) != 0)             /* oops, not a viable device */
        return(-1);

    if (biosdev < 0x80) {
        /* floppy (or emulated floppy) or ATAPI device */
        if (bdinfo[dev->d_kind.biosdisk.unit].bd_type == DT_ATAPI) {
            /* is an ATAPI disk */
            major = WFDMAJOR;
        } else {
            /* is a floppy disk */
            major = FDMAJOR;
        }
    } else {
        /* harddisk */
        if ((od->od_flags & BD_LABELOK) && (od->od_disklabel.d_type == DTYPE_SCSI)) {
            /* label OK, disk labelled as SCSI */
            major = DAMAJOR;
            /* check for unit number correction hint, now deprecated */
            if ((nip = getenv("num_ide_disks")) != NULL) {
                i = strtol(nip, &cp, 0);
                /* check for parse error */
                if ((cp != nip) && (*cp == 0))
                    unitofs = i;
            }
        } else {
            /* assume an IDE disk */
            major = WDMAJOR;
        }
    }
    /* default root disk unit number */
    unit = (biosdev & 0x7f) - unitofs;

    /* XXX a better kludge to set the root disk unit number */
    if ((nip = getenv("root_disk_unit")) != NULL) {
        i = strtol(nip, &cp, 0);
        /* check for parse error */
        if ((cp != nip) && (*cp == 0))
            unit = i;
    }

    rootdev = MAKEBOOTDEV(major, dev->d_kind.biosdisk.slice + 1, unit,
                          dev->d_kind.biosdisk.partition);
    DEBUG("dev is 0x%x\n", rootdev);
    return(rootdev);
}