freebsd-dev/usr.bin/doscmd/int13.c

/*
 * Copyright (c) 1992, 1993, 1996
 *	Berkeley Software Design, Inc.  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.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *	This product includes software developed by Berkeley Software
 *	Design, Inc.
 *
 * THIS SOFTWARE IS PROVIDED BY Berkeley Software Design, Inc. ``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 Berkeley Software Design, Inc. 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.
 *
 *	BSDI int13.c,v 2.3 1996/04/08 19:32:43 bostic Exp
 */

#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");

#include <sys/ioctl.h>
#include <sys/types.h>
#include <sys/uio.h>
#include <unistd.h>

#include "doscmd.h"

#define	FDCHANGED	_IOR('F', 64, int)

#define INT13_ERR_NONE               0x00
#define INT13_ERR_BAD_COMMAND        0x01
#define INT13_ERR_BAD_ADDRESS_MARK   0x02
#define INT13_ERR_WRITE_PROTECT      0x03
#define INT13_ERR_SECTOR_ID_BAD      0x04
#define INT13_ERR_RESET_FAILURE      0x05
#define INT13_ERR_CLL_ACTIVE         0x06
#define INT13_ERR_ACT_FAILED         0x07
#define INT13_ERR_DMA_OVERRUN        0x08
#define INT13_ERR_DMA_BOUNDARY       0x09
#define INT13_ERR_BAD_TRACK_FLAG     0x0B
#define INT13_ERR_MEDIA_TYP_UNKNOWN  0x0C
#define INT13_ERR_CRC                0x10
#define INT13_ERR_CORRECTED          0x11
#define INT13_ERR_CTRLR_FAILURE      0x20
#define INT13_ERR_SEEK               0x40
#define INT13_ERR_TIME_OUT           0x80
#define INT13_ERR_NOT_READY          0xAA
#define INT13_ERR_UNDEFINED          0xBB
#define INT13_ERR_SENSE_OPERATION    0xFF

typedef struct {
    u_char	bootIndicator;
    u_char	beginHead;
    u_char	beginSector;
    u_char	beginCyl;
    u_char	systemID;
    u_char	endHead;
    u_char	endSector;
    u_char	endCyl;
    u_long	relSector;
    u_long	numSectors;
} PTAB;

struct diskinfo {
    int		type;
    int		sectors;
    int		cylinders;
    int		sides;
    int		secsize;
    int		fd;
    char	*path;
    u_long	location;
    u_char	*sector0;
    u_long	offset;
    char	*list[4];		/* Up to 4 devices allowed */
    unsigned	multi:2;
    int		read_only:1;
    int		removeable:1;
    int		changed:1;		/* Set if we change format */
};

#define	hd_status	(*(u_char *)0x474)
#define	fd_status	(*(u_char *)0x441)

static __inline int
disize(struct diskinfo *di)
{
    return(di->sectors * di->cylinders * di->sides);
}

static __inline int
cylsize(struct diskinfo *di)
{
    return(di->sectors * di->sides);
}

static u_long ftable = 0xF1000;	/* Floppy table */
static u_long htable = 0xF1020;	/* Hard disk table */

static struct diskinfo diskinfo[26];

static struct diskinfo floppyinfo[] = {
    {0,  9, 40, 1, 512, -1, NULL, 0, NULL, 0,
     {NULL, NULL, NULL, NULL}, 0, 0, 0, 0}, /* Probably not correct */
    {1,  9, 40, 2, 512, -1, NULL, 0, NULL, 0,
     {NULL, NULL, NULL, NULL}, 0, 0, 0, 0},
    {2,  9, 80, 2, 512, -1, NULL, 0, NULL, 0,
     {NULL, NULL, NULL, NULL}, 0, 0, 0, 0},
    {3, 15, 80, 2, 512, -1, NULL, 0, NULL, 0,
     {NULL, NULL, NULL, NULL}, 0, 0, 0, 0},
    {4, 18, 80, 2, 512, -1, NULL, 0, NULL, 0,
     {NULL, NULL, NULL, NULL}, 0, 0, 0, 0},
    {6, 36, 80, 2, 512, -1, NULL, 0, NULL, 0,
     {NULL, NULL, NULL, NULL}, 0, 0, 0, 0},
    {-1, 0,  0, 0,   0,  0, NULL, 0, NULL, 0,
     {NULL, NULL, NULL, NULL}, 0, 0, 0, 0}
};

static struct diskinfo *
getdisk(int drive)
{
    struct diskinfo *di;

    if (drive >= 2 && drive < 0x80) {
	return(0);
    }
    if (drive >= 0x80) {
	drive -= 0x80;
	drive += 2;
    }

    if (drive > 25 || diskinfo[drive].path == 0) {
	return(0);
    }
    di = &diskinfo[drive];
    if (di->fd < 0) {
	if (di->removeable) {
	    di->read_only = 0;
	    if (!(di->path = di->list[di->multi]))
		di->path = di->list[di->multi = 0];
	    }	
	if ((di->fd = open(di->path, di->read_only ? O_RDONLY
			   : O_RDWR|O_FSYNC)) < 0 &&
	    (di->read_only = 1) &&
	    (di->fd = open(di->path, O_RDONLY)) < 0) {
	    return(0);
	}
	di->fd = squirrel_fd(di->fd);
    }
    return(di);
}

int
disk_fd(int drive)
{
    struct diskinfo *di;

    if (drive > 1)
	drive += 0x80 - 2;
    di = getdisk(drive);
    if (!di)
	return(-1);
    return(di->fd);
}

void
make_readonly(int drive)
{
    if (drive < 0 || drive >= 26)
	return;
    diskinfo[drive].read_only = 1;
}

int
init_hdisk(int drive, int cyl, int head, int tracksize, char *file, char *fake_ptab)
{
    struct diskinfo *di;
    u_long table;

    if (drive < 0) {
	for (drive = 2; drive < 26; ++drive) {
	    if (diskinfo[drive].path == 0)
		break;
	}
    }
    if (drive < 2) {
    	fprintf(stderr, "Only floppies may be assigned to A: or B:\n");
	return(-1);
    }

    if (drive >= 26) {
	fprintf(stderr, "Too many disk drives (only 24 allowed)\n");
	return(-1);
    }

    di = &diskinfo[drive];

    if (di->path) {
	fprintf(stderr, "Drive %c: already assigned to %s\n", drntol(drive),
			 di->path);
	return(-1);
    }
    di->fd = -1;
    di->sectors = tracksize;
    di->cylinders = cyl;
    di->sides = head;
    di->sector0 = 0;
    di->offset = 0;

    if (fake_ptab) {
	u_char buf[512];
	int fd;
	PTAB *ptab;
	int clusters;

    	if ((fd = open(fake_ptab, 0)) < 0) {
		perror(fake_ptab);
		return(-1);
	}
    	di->sector0 = malloc(512);
	if (!di->sector0) {
		perror("malloc in init_hdisk");
		quit(1);
	}

	read(fd, di->sector0, 512);
	close(fd);

    	ptab = (PTAB *)(di->sector0 + 0x01BE);

    	for (fd = 0; fd < 4; ++fd) {
	    if (*(u_short *)(di->sector0 + 0x1FE) == 0xAA55 &&
	        ptab[fd].numSectors == (u_long)(head * tracksize * cyl) &&
		(ptab[fd].systemID == 1 || ptab[fd].systemID == 4 ||
		 ptab[fd].systemID == 6))
		    break;
    	}
    	if (fd < 4) {
	    if (fd)
		memcpy(ptab, ptab + fd, sizeof(PTAB));
	    memset(ptab + 1, 0, sizeof(PTAB) * 3);
	    di->offset = ptab[0].relSector;
	    di->cylinders += di->offset / cylsize(di);
	} else {
	    memset(ptab, 0, sizeof(PTAB) * 4);

	    ptab->beginHead = 0;
	    ptab->beginSector = 1;	/* this is 1 based */
	    ptab->beginCyl = 1;

	    ptab->endHead = head - 1;
	    ptab->endSector = tracksize;	/* this is 1 based */
	    ptab->endCyl = cyl & 0xff;
	    ptab->endSector |= (cyl & 0x300) >> 2;

	    ptab->relSector = head * tracksize;
	    ptab->numSectors = head * tracksize * cyl;
	    
	    *(u_short *)(di->sector0 + 0x1FE) = 0xAA55;

	    fd = open(file, 0);
	    if (fd < 0) {
		perror(file);
		return(-1);
	    }
	    memset(buf, 0, 512);
	    read(fd, buf, 512);
	    close(fd);
	    if ((clusters = buf[0x0D]) == 0) {
		if (disize(di) <= 128 * 2048)
		    clusters = 4;
		else if (disize(di) <= 256 * 2048)
		    clusters = 8;
		else if (disize(di) <= 8 * 1024 * 2048)
		    clusters = 16;
		else if (disize(di) <= 16 * 1024 * 2048)
		    clusters = 32;
		else
		    clusters = 64;
	    }
	    if ((disize(di) / clusters) <= 4096) {
		ptab->systemID = 0x01;
	    } else {
		ptab->systemID = 0x04;
	    }

	    di->cylinders += 1;	/* Extra cylinder for partition table, etc. */
	}
	ptab->bootIndicator = 0x80;
    }
    di->type = 0xf8;
    di->path = file;
    di->secsize = 512;
    di->path = strdup(file);

    di->location = ((table & 0xf0000) << 12) | (table & 0xffff);

    if (drive == 0) {
	ivec[0x41] = di->location;
    } else if (drive == 1) {
	ivec[0x46] = di->location;
    }

    table = htable + (drive - 2) * 0x10;
    *(u_short *)(table+0x00) = di->cylinders-1;	/* Cylinders */
    *(u_char  *)(table+0x02) = di->sides;	/* Heads */
    *(u_short *)(table+0x03) = 0;		/* 0 */
    *(u_short *)(table+0x05) = 0xffff;		/* write pre-comp */
    *(u_char  *)(table+0x07) = 0;		/* ECC Burst length */
    *(u_char  *)(table+0x08) = 0;		/* Control Byte */
    *(u_char  *)(table+0x09) = 0;		/* standard timeout */
    *(u_char  *)(table+0x0a) = 0;		/* formatting timeout */
    *(u_char  *)(table+0x0b) = 0;		/* timeout for checking drive */
    *(u_short *)(table+0x0c) = di->cylinders-1;	/* landing zone */
    *(u_char  *)(table+0x0e) = di->sectors;	/* sectors/track */
    *(u_char  *)(table+0x0f) = 0;

    if ((drive - 1) >= ndisks)
	ndisks = drive - 1;
    return(drive);
}

static __inline int
bps(int size)
{
    switch (size) {
    case 128:	return(0);
    case 256:	return(1);
    case 512:	return(2);
    case 1024:	return(3);
    default:
	fprintf(stderr, "Invalid sector size: %d\n", size);
	quit(1);
    }
    /* keep `gcc -Wall' happy */
    return(0);
}

int
init_floppy(int drive, int type, char *file)
{
    struct diskinfo *di = floppyinfo;
    u_long table;
    struct stat sb;

    while (di->type >= 0 && di->type != type && disize(di)/2 != type)
	++di;

    if (!di->type) {
	fprintf(stderr, "Invalid floppy type: %d\n", type);
	return(-1);
    }

    if (drive < 0) {
    	if (diskinfo[0].path == 0) {
	    drive = 0;
    	} else if (diskinfo[1].path == 0) {
	    drive = 1;
	} else {
	    fprintf(stderr, "Too many floppy drives (only 2 allowed)\n");
	    return(-1);
    	}
    }
    if (drive > 1) {
	fprintf(stderr, "Floppies must be either drive A: or B:\n");
	return(-1);
    }

    if (drive >= nfloppies)
	nfloppies = drive + 1;

    if (diskinfo[drive].path == 0) {
	diskinfo[drive] = *di;
    }

    di = &diskinfo[drive];

    if (stat(file, &sb) < 0) {
	fprintf(stderr, "Drive %c: Could not stat %s\n", drntol(drive), file);
	return(-1);
    }

    if (drive < 2 && (S_ISCHR(sb.st_mode) || S_ISBLK(sb.st_mode))) {
	if (di->path && !di->removeable) {
	    fprintf(stderr, "Drive %c: is not removeable and hence can only have one assignment\n", drntol(drive));
	    return(-1);
	}
	di->removeable = 1;
    } else if (di->removeable) {
	fprintf(stderr, "Drive %c: already assigned to %s\n", drntol(drive),
			 di->path);
	return(-1);
    }

    if (di->removeable) {
#if 0 /*XXXXX*/
	if (di->multi == 4) {
	    fprintf(stderr, "Drive %c: already assigned 4 devices\n",
			     drntol(drive));
	    return(-1);
	}
#endif
	di->path = di->list[di->multi++] = strdup(file);
    } else {
	if (di->path) {
	    fprintf(stderr, "Drive %c: already assigned to %s\n",
			     drntol(drive), di->path);
	    return(-1);
	}

	di->path = strdup(file);
    }
    di->fd = -1;
    di->location = ((table & 0xf0000) << 12) | (table & 0xffff);
    di->sector0 = 0;
    di->offset = 0;

    ivec[0x1e] = ((ftable & 0xf0000) << 12) | (ftable & 0xffff);

    table = ftable + drive * 0x0a;

    *(u_char *)(table+0x00) = 0xdf;	/* First Specify Byte */
    *(u_char *)(table+0x01) = 0x02;	/* Second Specify Byte */
    *(u_char *)(table+0x02) = 0x25;	/* Timer ticks to wait 'til motor OFF */
    *(u_char *)(table+0x03) = bps(di->secsize);	/* Number of bytes/sector */
    *(u_char *)(table+0x04) = di->sectors;	/* Number of sectors/track */
    *(u_char *)(table+0x05) = 0x1b;	/* Gap length, in bytes */
    *(u_char *)(table+0x06) = 0xff;	/* Data length, in bytes */
    *(u_char *)(table+0x07) = 0x6c;	/* Gap length for format */
    *(u_char *)(table+0x09) = 0xf6;	/* Fill byte for formatting */
    *(u_char *)(table+0x09) = 0x0f;	/* Head settle time, in milliseconds */
    *(u_char *)(table+0x0a) = 0x08;	/* Motor startup time, in 1/8 seconds */
    return(drive);
}

int
search_floppy(int i)
{
    return(i < nfloppies ? diskinfo[i].type : 0);
}

#define	seterror(err)	{			\
    if (drive & 0x80)				\
	hd_status = err; 			\
    else					\
	fd_status = err;			\
    R_AH = err;					\
    R_FLAGS |= PSL_C;				\
}
	    
static int
trynext(struct diskinfo *di)
{
    close(di->fd);
    di->fd = -1;
    di->changed = 1;
#if 0 /*XXXXX*/
    if (di->multi++ >= 4)
	return(0);
#endif
    if (di->list[di->multi] && (di = getdisk(di - diskinfo))) {
	di->multi = 0;
	return(1);
    }
    return(0);
}

static int
diread(struct diskinfo *di, regcontext_t *REGS,
       off_t start, char *addr, int sectors)
{
    off_t res;

    int drive = di - diskinfo;
    di->multi = -1;

    if (drive > 1) {
	drive -= 2;
	drive |= 0x80;
    }

again:
    res = lseek(di->fd, start * di->secsize, 0);

    if (res < 0 && di->removeable && trynext(di))
	goto again;

    if (res < 0) {
	seterror(INT13_ERR_SEEK);
	return(-1);
    }

    res = read(di->fd, addr, sectors * di->secsize);

    if (res < 0 && di->removeable && trynext(di))
	goto again;

    if (di->removeable) {
	if (res < 0) {
	    seterror(INT13_ERR_NOT_READY);
	    return(-1);
	}
	return(res / di->secsize);
    }

    /*
     * reads always work, if if they don't.
     * Just pretend any byte not read was actually a 0
     */
    if (res < 0)
	memset(addr, 0, sectors * di->secsize);
    else if (res < sectors * di->secsize)
	memset(addr + res, 0, sectors * di->secsize - res);
	
    return(sectors);
}

static int
diwrite(struct diskinfo *di, regcontext_t *REGS,
       off_t start, char *addr, int sectors)
{
    off_t res;
    int drive = di - diskinfo;
    di->multi = -1;

    if (drive > 1) {
	drive -= 2;
	drive |= 0x80;
    }

again:
    res = lseek(di->fd, start * di->secsize, 0);
    
    if (res < 0 && di->removeable && trynext(di))
	goto again;

    if (res < 0) {
	seterror(INT13_ERR_SEEK);
	return(-1);
    }

    res = write(di->fd, addr, sectors * di->secsize);
    
    if (res < 0 && di->removeable && trynext(di))
	goto again;
    
    if (di->removeable) {
	if (res < 0) {
	    seterror(INT13_ERR_NOT_READY);
	    return(-1);
	}
    } else if (res < 0) {
	seterror(INT13_ERR_WRITE_PROTECT);
	return(-1);
    }
    return(res / di->secsize);
}

static void
int13(regcontext_t *REGS)
{
    char *addr;
    int sectors;
    struct diskinfo *di;
    off_t start;
    int did;

    int cyl;
    int sector;
    int side;
    int drive;
    
    reset_poll();

    R_FLAGS &= ~PSL_C;

    drive = R_DL;

    if (R_AX != 0x01) {
	if (drive & 0x80) 
	    hd_status = 0;
	else
	    fd_status = 0;
    }

    switch (R_AH) {
    case 0x00:	/* Reset */
	break;
    case 0x01:	/* Read disk status */ 
	if (drive & 0x80) 
	    R_AH = hd_status;
	else
	    R_AH = fd_status;
	if (R_AH)
	    R_FLAGS |= PSL_C;
	break;
	case 0x02:	/* Read */
	    R_AH = 0;
	    addr = (char *)MAKEPTR(R_ES, R_BX);
	    sectors = R_AL;
	    side = R_DH;
	    R_AL = 0;		/* Start out with nothing read */

	    if (drive & 0x80) {
		cyl = R_CH | ((R_CL & 0xc0) << 2);
		sector = (R_CL & 0x3f) - 1;
	    } else {
		sector = R_CL - 1;
		cyl = R_CH;
	    }

	    if ((di = getdisk(drive)) == 0) {
		debug(D_DISK, "Bad drive: %02x (%d : %d : %d)\n",
		      drive, cyl, side, sector);
		seterror(INT13_ERR_BAD_COMMAND);
		break;
	    }
	    start = cyl * di->sectors * di->sides +
		side * di->sectors +
		sector;

	    if (start >= disize(di)) {
		debug(D_DISK, "Read past end of disk\n");
		seterror(INT13_ERR_SEEK);
		break;
	    }
	    if (sectors + start >= disize(di)) {
		sectors = disize(di) - start;
	    }

	    if (di->sector0) {
		if (start < di->offset) {
		    R_AL = sectors;
		    if (start == 0) {
			memcpy(addr, di->sector0, di->secsize);
			addr += di->secsize;
			--sectors;
		    }
		    memset(addr, 0, sectors * di->secsize);
		    break;
		} else {
		    start -= di->offset;
		}
	    }
	    debug(D_DISK, "%02x: Read %2d sectors from %qd to %04x:%04x\n",
		  drive, sectors, start, R_ES, R_BX);

	    if ((did = diread(di, REGS, start, addr, sectors)) >= 0)
		R_AL = did;
#if 0
	    callint(0x0d);
	    callint(0x76);
#endif
	    break;

	case 0x03:	/* Write */
	    R_AH = 0;
	    addr = (char *)MAKEPTR(R_ES, R_BX);
	    sectors = R_AL;
	    side = R_DH;
	    R_AL = 0;	/* Start out with nothing written */

	    if (drive & 0x80) {
		cyl = R_CH | ((R_CL & 0xc0) << 2);
		sector = (R_CL & 0x3f) - 1;
	    } else {
		sector = R_CL - 1;
		cyl = R_CH;
	    }

	    if ((di = getdisk(drive)) == 0) {
		debug(D_DISK, "Bad drive: %d (%d : %d : %d)\n",
		      drive, cyl, side, sector);
		seterror(INT13_ERR_BAD_COMMAND);
		break;
	    }
	    if (di->read_only) {
		debug(D_DISK, "%02x: Attempt to write readonly disk\n", drive);
		seterror(INT13_ERR_WRITE_PROTECT);
		break;
	    }
	    start = cyl * di->sectors * di->sides +
		side * di->sectors +
		sector;
	    
	    if (start >= disize(di)) {
		debug(D_DISK, "Write past end of disk\n");
		seterror(INT13_ERR_SEEK);
		break;
	    }

	    if (sectors + start >= disize(di))
		sectors = disize(di) - start;

	    if (di->sector0) {
		if (start < di->offset) {
		    R_AL = sectors;
		    break;
		} else {
		    start -= di->offset;
		}
	    }

	    debug(D_DISK, "%02x: Write %2d sectors from %qd to %04x:%04x\n",
		  drive, sectors, start, R_ES, R_BX);

	    if ((did = diwrite(di, REGS, start, addr, sectors)) >= 0)
		R_AL = did;
#if 0
	    callint(0x0d);
	    callint(0x76);
#endif
	    break;

    	case 0x04:	/* Verify */
	    R_AH = 0;
	    sectors = R_AL;
	    side = R_DH;

	    if (drive & 0x80) {
		cyl = R_CH | ((R_CL & 0xc0) << 2);
		sector = (R_CL & 0x3f) - 1;
	    } else {
		sector = R_CL - 1;
		cyl = R_CH;
	    }

	    if ((di = getdisk(drive)) == 0) {
		debug(D_DISK, "Bad drive: %d (%d : %d : %d)\n",
		      drive, cyl, side, sector);
		seterror(INT13_ERR_BAD_COMMAND);
		break;
	    }
	    start = cyl * di->sectors * di->sides +
		side * di->sectors +
		sector;
	    
	    if (start >= disize(di)) {
		debug(D_DISK, "Verify past end of disk\n");
		seterror(INT13_ERR_SEEK);
		break;
	    }

	    if (sectors + start >= disize(di))
		sectors = disize(di) - start;

	    if (di->sector0) {
		if (start < di->offset)
		    break;
		else
		    start -= di->offset;
	    }

	    debug(D_DISK, "Verify %2d sectors from %qd\n", sectors, start);
	    if (lseek(di->fd, start * di->secsize, 0) < 0) {
		debug(D_DISK, "Seek error\n");
		seterror(INT13_ERR_SEEK);
		break;
	    }
	    while (sectors > 0) {
		char buf[512];
		if (read(di->fd, buf, di->secsize) != di->secsize) {
		    debug(D_DISK, "Verify error\n");
		    seterror(0x04);
		    break;
		}
		--sectors;
	    }
#if 0
	    callint(0x0d);
	    callint(0x76);
#endif
	    break;
    
    case 0x05:	/* Format track */
	seterror(INT13_ERR_BAD_COMMAND);
	break;

    case 0x08:	/* Status */
	R_AH = 0;

	if ((di = getdisk(drive)) == 0) {
	    debug(D_DISK, "Bad drive: %d\n", drive);
	    seterror(INT13_ERR_BAD_COMMAND);
	    break;
	}
	R_AX = 0;

	R_BX = di->type;
	if ((drive & 0x80) == 0)
	    PUTVEC(R_ES, R_DI, di->location);

	R_CL = di->sectors | ((di->cylinders >> 2) & 0xc0);
	R_CH = di->cylinders & 0xff;
	R_DL = (drive & 0x80) ? ndisks : nfloppies;
	R_DH = di->sides - 1;
	debug(D_DISK, "%02x: Status requested: sec %d cyl %d side %d drive %d\n", 
	      drive, R_CL, R_CH, R_DH, R_DL);
#if 0
	callint(0x0d);
	callint(0x76);
#endif
	break;

    case 0x0c:	/* Move read/write head */
    case 0x0d:	/* Reset */
	break;

    case 0x10:	/* check for disk ready */
	R_AH = 0;	/* always open for business */
	break;
	    
    case 0x15:
	if ((di = getdisk(drive)) == 0) {
	    R_AH = 0;
	    R_FLAGS |= PSL_C;
	    break;
	}

	if (drive & 0x80) {
	    start = di->sectors * di->cylinders * di->sides;
	    R_CX = start >> 16;
	    R_DX = start;
	    R_AH = 3;
	} else {
	    R_AH = 1;	/* Non-changeable disk */
	}
	break;

    case 0x16:	/* Media change */
	R_AH = 0;
	if ((di = getdisk(drive)) && di->changed) {
	    di->changed = 0;
	    R_AH = 6;
	}
	break;

    case 0x17:	/* Determine floppy disk format */
	seterror(INT13_ERR_BAD_COMMAND);
	break;
	
    case 0x18:	/* Determine disk format */
	if ((di = getdisk(drive)) == 0) {
	    R_AH = 0;
	    R_FLAGS |= PSL_C;
	    break;
	}
	/* XXX incomplete? */
	break;

    default:
	unknown_int2(0x13, R_AH, REGS);
	break;
    }
}

void
disk_bios_init(void)
{
    u_long vec;

    vec = insert_softint_trampoline();
    ivec[0x13] = vec;
    register_callback(vec, int13, "int 13");
    
    vec = insert_null_trampoline();
    ivec[0x76] = vec;
}