trunk/src/diskimage.c

/*
 *  Copyright (C) 2003-2006  Anders Gavare.  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. The name of the author may not be used to endorse or promote products
 *     derived from this software without specific prior written permission.
 *
 *  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.
 *
 *
 *  $Id: diskimage.c,v 1.110 2006/06/24 19:52:27 debug Exp $
 *
 *  Disk image support.
 *
 *  TODO:  There's probably a bug in the tape support:
 *         Let's say there are 10240 bytes left in a file, and 10240
 *         bytes are read. Then feof() is not true yet (?), so the next
 *         read will also return 10240 bytes (but all zeroes), and then after
 *         that return feof (which results in a filemark).  This is probably
 *         trivial to fix, but I don't feel like it right now.
 *
 *  TODO:  diskimage_remove()? This would be useful for floppies in PC-style
 *         machines, where disks may need to be swapped during boot etc.
 */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h>

#include "cpu.h"
#include "diskimage.h"
#include "machine.h"
#include "misc.h"


/*  #define debug fatal  */

extern int single_step;

static char *diskimage_types[] = DISKIMAGE_TYPES;

static struct scsi_transfer *first_free_scsi_transfer_alloc = NULL;


/**************************************************************************/

/*
 *  my_fseek():
 *
 *  A helper function, like fseek() but takes off_t.  If the system has
 *  fseeko, then that is used. Otherwise I try to fake off_t offsets here.
 *
 *  The correct position is reached by seeking 2 billion bytes at a time
 *  (or less).  Note: This method is only used for SEEK_SET, for SEEK_CUR
 *  and SEEK_END, normal fseek() is used!
 *
 *  TODO: It seemed to work on Linux/i386, but not on Solaris/sparc (?).
 *  Anyway, most modern systems have fseeko(), so it shouldn't be a problem.
 */
static int my_fseek(FILE *f, off_t offset, int whence)
{
#ifdef HACK_FSEEKO
        if (whence == SEEK_SET) {
                int res = 0;
                off_t curoff = 0;
                off_t cur_step;

                fseek(f, 0, SEEK_SET);
                while (curoff < offset) {
                        /*  How far to seek?  */
                        cur_step = offset - curoff;
                        if (cur_step > 2000000000)
                                cur_step = 2000000000;
                        res = fseek(f, cur_step, SEEK_CUR);
                        if (res)
                                return res;
                        curoff += cur_step;
                }
                return 0;
        } else
                return fseek(f, offset, whence);
#else
        return fseeko(f, offset, whence);
#endif
}


/**************************************************************************/


/*
 *  scsi_transfer_alloc():
 *
 *  Allocates memory for a new scsi_transfer struct, and fills it with
 *  sane data (NULL pointers).
 *  The return value is a pointer to the new struct.  If allocation
 *  failed, the program exits.
 */
struct scsi_transfer *scsi_transfer_alloc(void)
{
        struct scsi_transfer *p;

        if (first_free_scsi_transfer_alloc != NULL) {
                p = first_free_scsi_transfer_alloc;
                first_free_scsi_transfer_alloc = p->next_free;
        } else {
                p = malloc(sizeof(struct scsi_transfer));
                if (p == NULL) {
                        fprintf(stderr, "scsi_transfer_alloc(): out "
                            "of memory\n");
                        exit(1);
                }
        }

        memset(p, 0, sizeof(struct scsi_transfer));

        return p;
}


/*
 *  scsi_transfer_free():
 *
 *  Frees the space used by a scsi_transfer struct.  All buffers refered
 *  to by the scsi_transfer struct are freed.
 */
void scsi_transfer_free(struct scsi_transfer *p)
{
        if (p == NULL) {
                fprintf(stderr, "scsi_transfer_free(): p == NULL\n");
                exit(1);
        }

        if (p->msg_out != NULL)
                free(p->msg_out);
        if (p->cmd != NULL)
                free(p->cmd);
        if (p->data_out != NULL)
                free(p->data_out);

        if (p->data_in != NULL)
                free(p->data_in);
        if (p->msg_in != NULL)
                free(p->msg_in);
        if (p->status != NULL)
                free(p->status);

        p->next_free = first_free_scsi_transfer_alloc;
        first_free_scsi_transfer_alloc = p;
}


/*
 *  scsi_transfer_allocbuf():
 *
 *  Helper function, used by diskimage_scsicommand(), and SCSI controller
 *  devices.  Example of usage:
 *
 *      scsi_transfer_allocbuf(&xferp->msg_in_len, &xferp->msg_in, 1);
 */
void scsi_transfer_allocbuf(size_t *lenp, unsigned char **pp, size_t want_len,
        int clearflag)
{
        unsigned char *p = (*pp);

        if (p != NULL) {
                printf("WARNING! scsi_transfer_allocbuf(): old pointer "
                    "was not NULL, freeing it now\n");
                free(p);
        }

        (*lenp) = want_len;
        if ((p = malloc(want_len)) == NULL) {
                fprintf(stderr, "scsi_transfer_allocbuf(): out of "
                    "memory trying to allocate %li bytes\n", (long)want_len);
                exit(1);
        }

        if (clearflag)
                memset(p, 0, want_len);

        (*pp) = p;
}


/**************************************************************************/


/*
 *  diskimage_exist():
 *
 *  Returns 1 if the specified disk id (for a specific type) exists, 0
 *  otherwise.
 */
int diskimage_exist(struct machine *machine, int id, int type)
{
        struct diskimage *d = machine->first_diskimage;

        while (d != NULL) {
                if (d->type == type && d->id == id)
                        return 1;
                d = d->next;
        }
        return 0;
}


/*
 *  diskimage_recalc_size():
 *
 *  Recalculate a disk's size by stat()-ing it.
 *  d is assumed to be non-NULL.
 */
static void diskimage_recalc_size(struct diskimage *d)
{
        struct stat st;
        int res;
        off_t size = 0;

        res = stat(d->fname, &st);
        if (res) {
                fprintf(stderr, "[ diskimage_recalc_size(): could not stat "
                    "'%s' ]\n", d->fname);
                return;
        }

        size = st.st_size;

        /*
         *  TODO:  CD-ROM devices, such as /dev/cd0c, how can one
         *  check how much data is on that cd-rom without reading it?
         *  For now, assume some large number, hopefully it will be
         *  enough to hold any cd-rom image.
         */
        if (d->is_a_cdrom && size == 0)
                size = 762048000;

        d->total_size = size;
        d->ncyls = d->total_size / 1048576;

        /*  TODO: There is a mismatch between d->ncyls and d->cylinders,
            SCSI-based stuff usually doesn't care.  TODO: Fix this.  */
}


/*
 *  diskimage_getsize():
 *
 *  Returns -1 if the specified disk id/type does not exists, otherwise
 *  the size of the disk image is returned.
 */
int64_t diskimage_getsize(struct machine *machine, int id, int type)
{
        struct diskimage *d = machine->first_diskimage;

        while (d != NULL) {
                if (d->type == type && d->id == id)
                        return d->total_size;
                d = d->next;
        }
        return -1;
}


/*
 *  diskimage_getchs():
 *
 *  Returns the current CHS values of a disk image.
 */
void diskimage_getchs(struct machine *machine, int id, int type,
        int *c, int *h, int *s)
{
        struct diskimage *d = machine->first_diskimage;

        while (d != NULL) {
                if (d->type == type && d->id == id) {
                        *c = d->cylinders;
                        *h = d->heads;
                        *s = d->sectors_per_track;
                        return;
                }
                d = d->next;
        }
        fatal("diskimage_getchs(): disk id %i (type %i) not found?\n",
            id, diskimage_types[type]);
        exit(1);
}


/*
 *  diskimage__return_default_status_and_message():
 *
 *  Set the status and msg_in parts of a scsi_transfer struct
 *  to default values (msg_in = 0x00, status = 0x00).
 */
static void diskimage__return_default_status_and_message(
        struct scsi_transfer *xferp)
{
        scsi_transfer_allocbuf(&xferp->status_len, &xferp->status, 1, 0);
        xferp->status[0] = 0x00;
        scsi_transfer_allocbuf(&xferp->msg_in_len, &xferp->msg_in, 1, 0);
        xferp->msg_in[0] = 0x00;
}


/*
 *  diskimage__switch_tape():
 *
 *  Used by the SPACE command.  (d is assumed to be non-NULL.)
 */
static void diskimage__switch_tape(struct diskimage *d)
{
        char tmpfname[1000];

        snprintf(tmpfname, sizeof(tmpfname), "%s.%i",
            d->fname, d->tape_filenr);
        tmpfname[sizeof(tmpfname)-1] = '\0';

        if (d->f != NULL)
                fclose(d->f);

        d->f = fopen(tmpfname, d->writable? "r+" : "r");
        if (d->f == NULL) {
                fprintf(stderr, "[ diskimage__switch_tape(): could not "
                    "(re)open '%s' ]\n", tmpfname);
                /*  TODO: return error  */
        }
        d->tape_offset = 0;
}


/*
 *  diskimage_access__cdrom():
 *
 *  This is a special-case function, called from diskimage__internal_access().
 *  On my FreeBSD 4.9 system, the cdrom device /dev/cd0c seems to not be able
 *  to handle something like "fseek(512); fread(512);" but it handles
 *  "fseek(2048); fread(512);" just fine.  So, if diskimage__internal_access()
 *  fails in reading a block of data, this function is called as an attempt to
 *  align reads at 2048-byte sectors instead.
 *
 *  (Ugly hack.  TODO: how to solve this cleanly?)
 *
 *  NOTE:  Returns the number of bytes read, 0 if nothing was successfully
 *  read. (These are not the same as diskimage_access()).
 */
#define CDROM_SECTOR_SIZE       2048
static size_t diskimage_access__cdrom(struct diskimage *d, off_t offset,
        unsigned char *buf, size_t len)
{
        off_t aligned_offset;
        size_t bytes_read, total_copied = 0;
        unsigned char cdrom_buf[CDROM_SECTOR_SIZE];
        off_t buf_ofs, i = 0;

        /*  printf("diskimage_access__cdrom(): offset=0x%llx size=%lli\n",
            (long long)offset, (long long)len);  */

        aligned_offset = (offset / CDROM_SECTOR_SIZE) * CDROM_SECTOR_SIZE;
        my_fseek(d->f, aligned_offset, SEEK_SET);

        while (len != 0) {
                bytes_read = fread(cdrom_buf, 1, CDROM_SECTOR_SIZE, d->f);
                if (bytes_read != CDROM_SECTOR_SIZE)
                        return 0;

                /*  Copy (part of) cdrom_buf into buf:  */
                buf_ofs = offset - aligned_offset;
                while (buf_ofs < CDROM_SECTOR_SIZE && len != 0) {
                        buf[i ++] = cdrom_buf[buf_ofs ++];
                        total_copied ++;
                        len --;
                }

                aligned_offset += CDROM_SECTOR_SIZE;
                offset = aligned_offset;
        }

        return total_copied;
}


/*
 *  diskimage__internal_access():
 *
 *  Read from or write to a struct diskimage.
 *
 *  Returns 1 if the access completed successfully, 0 otherwise.
 */
static int diskimage__internal_access(struct diskimage *d, int writeflag,
        off_t offset, unsigned char *buf, size_t len)
{
        ssize_t lendone;
        int res;

        if (buf == NULL) {
                fprintf(stderr, "diskimage__internal_access(): buf = NULL\n");
                exit(1);
        }
        if (len == 0)
                return 1;
        if (d->f == NULL)
                return 0;

        res = my_fseek(d->f, offset, SEEK_SET);
        if (res != 0) {
                fatal("[ diskimage__internal_access(): fseek() failed on "
                    "disk id %i \n", d->id);
                return 0;
        }

        if (writeflag) {
                if (!d->writable)
                        return 0;

                lendone = fwrite(buf, 1, len, d->f);
        } else {
                /*
                 *  Special case for CD-ROMs. Actually, this is not needed
                 *  for .iso images, only for physical CDROMS on some OSes,
                 *  such as FreeBSD.
                 */
                if (d->is_a_cdrom)
                        lendone = diskimage_access__cdrom(d, offset, buf, len);
                else
                        lendone = fread(buf, 1, len, d->f);

                if (lendone < (ssize_t)len)
                        memset(buf + lendone, 0, len - lendone);
        }

        /*  Warn about non-complete data transfers:  */
        if (lendone != (ssize_t)len) {
                fatal("[ diskimage__internal_access(): disk_id %i, offset %lli"
                    ", transfer not completed. len=%i, len_done=%i ]\n",
                    d->id, (long long)offset, (int)len, (int)lendone);
                return 0;
        }

        return 1;
}


/*
 *  diskimage_scsicommand():
 *
 *  Perform a SCSI command on a disk image.
 *
 *  The xferp points to a scsi_transfer struct, containing msg_out, command,
 *  and data_out coming from the SCSI controller device.  This function
 *  interprets the command, and (if necessary) creates responses in
 *  data_in, msg_in, and status.
 *
 *  Returns:
 *      2 if the command expects data from the DATA_OUT phase,
 *      1 if otherwise ok,
 *      0 on error.
 */
int diskimage_scsicommand(struct cpu *cpu, int id, int type,
        struct scsi_transfer *xferp)
{
        char namebuf[16];
        int retlen, i, q;
        uint64_t size;
        int64_t ofs;
        int pagecode;
        struct machine *machine = cpu->machine;
        struct diskimage *d;

        if (machine == NULL) {
                fatal("[ diskimage_scsicommand(): machine == NULL ]\n");
                return 0;
        }

        d = machine->first_diskimage;
        while (d != NULL) {
                if (d->type == type && d->id == id)
                        break;
                d = d->next;
        }
        if (d == NULL) {
                fprintf(stderr, "[ diskimage_scsicommand(): %s "
                    " id %i not connected? ]\n", diskimage_types[type], id);
        }

        if (xferp->cmd == NULL) {
                fatal("[ diskimage_scsicommand(): cmd == NULL ]\n");
                return 0;
        }

        if (xferp->cmd_len < 1) {
                fatal("[ diskimage_scsicommand(): cmd_len == %i ]\n",
                    xferp->cmd_len);
                return 0;
        }

        debug("[ diskimage_scsicommand(id=%i) cmd=0x%02x: ",
            id, xferp->cmd[0]);

#if 0
        fatal("[ diskimage_scsicommand(id=%i) cmd=0x%02x len=%i:",
            id, xferp->cmd[0], xferp->cmd_len);
        for (i=0; i<xferp->cmd_len; i++)
                fatal(" %02x", xferp->cmd[i]);
        fatal("\n");
if (xferp->cmd_len > 7 && xferp->cmd[5] == 0x11)
        single_step = ENTER_SINGLE_STEPPING;
#endif

#if 0
{
        static FILE *f = NULL;
        if (f == NULL)
                f = fopen("scsi_log.txt", "w"); 
        if (f != NULL) {
                int i;
                fprintf(f, "id=%i cmd =", id);
                for (i=0; i<xferp->cmd_len; i++)
                        fprintf(f, " %02x", xferp->cmd[i]);
                fprintf(f, "\n");
                fflush(f);
        }
}
#endif

        switch (xferp->cmd[0]) {

        case SCSICMD_TEST_UNIT_READY:
                debug("TEST_UNIT_READY");
                if (xferp->cmd_len != 6)
                        debug(" (weird len=%i)", xferp->cmd_len);

                /*  TODO: bits 765 of buf[1] contains the LUN  */
                if (xferp->cmd[1] != 0x00)
                        fatal("WARNING: TEST_UNIT_READY with cmd[1]=0x%02x"
                            " not yet implemented\n", (int)xferp->cmd[1]);

                diskimage__return_default_status_and_message(xferp);
                break;

        case SCSICMD_INQUIRY:
                debug("INQUIRY");
                if (xferp->cmd_len != 6)
                        debug(" (weird len=%i)", xferp->cmd_len);
                if (xferp->cmd[1] != 0x00) {
                        debug("WARNING: INQUIRY with cmd[1]=0x%02x not yet "
                            "implemented\n", (int)xferp->cmd[1]);

                        break;
                }

                /*  Return values:  */
                retlen = xferp->cmd[4];
                if (retlen < 36) {
                        fatal("WARNING: SCSI inquiry len=%i, <36!\n", retlen);
                        retlen = 36;
                }

                /*  Return data:  */
                scsi_transfer_allocbuf(&xferp->data_in_len, &xferp->data_in,
                    retlen, 1);
                xferp->data_in[0] = 0x00;  /*  0x00 = Direct-access disk  */
                xferp->data_in[1] = 0x00;  /*  0x00 = non-removable  */
                xferp->data_in[2] = 0x02;  /*  SCSI-2  */
#if 0
xferp->data_in[3] = 0x02;       /*  Response data format = SCSI-2  */
#endif
                xferp->data_in[4] = retlen - 4; /*  Additional length  */
xferp->data_in[4] = 0x2c - 4;   /*  Additional length  */
                xferp->data_in[6] = 0x04;  /*  ACKREQQ  */
                xferp->data_in[7] = 0x60;  /*  WBus32, WBus16  */

                /*  These are padded with spaces:  */

                memcpy(xferp->data_in+8,  "GXemul  ", 8);
                if (diskimage_getname(cpu->machine, id,
                    type, namebuf, sizeof(namebuf))) {
                        size_t i;
                        for (i=0; i<sizeof(namebuf); i++)
                                if (namebuf[i] == 0) {
                                        for (; i<sizeof(namebuf); i++)
                                                namebuf[i] = ' ';
                                        break;
                                }
                        memcpy(xferp->data_in+16, namebuf, 16);
                } else
                        memcpy(xferp->data_in+16, "DISK            ", 16);
                memcpy(xferp->data_in+32, "0   ", 4);

                /*
                 *  Some Ultrix kernels want specific responses from
                 *  the drives.
                 */

                if (machine->machine_type == MACHINE_PMAX) {
                        /*  DEC, RZ25 (rev 0900) = 832527 sectors  */
                        /*  DEC, RZ58 (rev 2000) = 2698061 sectors  */
                        memcpy(xferp->data_in+8,  "DEC     ", 8);
                        memcpy(xferp->data_in+16, "RZ58     (C) DEC", 16);
                        memcpy(xferp->data_in+32, "2000", 4);
                }

                /*  Some data is different for CD-ROM drives:  */
                if (d->is_a_cdrom) {
                        xferp->data_in[0] = 0x05;  /*  0x05 = CD-ROM  */
                        xferp->data_in[1] = 0x80;  /*  0x80 = removable  */
                        /*  memcpy(xferp->data_in+16, "CD-ROM          ", 16);*/

                        if (machine->machine_type == MACHINE_PMAX) {
                                /*  SONY, CD-ROM:  */
                                memcpy(xferp->data_in+8, "SONY    ", 8);
                                memcpy(xferp->data_in+16,
                                    "CD-ROM          ", 16);

                                /*  ... or perhaps this:  */
                                memcpy(xferp->data_in+8, "DEC     ", 8);
                                memcpy(xferp->data_in+16,
                                    "RRD42   (C) DEC ", 16);
                                memcpy(xferp->data_in+32, "4.5d", 4);
                        } else if (machine->machine_type == MACHINE_ARC) {
                                /*  NEC, CD-ROM:  */
                                memcpy(xferp->data_in+8, "NEC     ", 8);
                                memcpy(xferp->data_in+16,
                                    "CD-ROM CDR-210P ", 16);
                                memcpy(xferp->data_in+32, "1.0 ", 4);
                        }
                }

                /*  Data for tape devices:  */
                if (d->is_a_tape) {
                        xferp->data_in[0] = 0x01;  /*  0x01 = tape  */
                        xferp->data_in[1] = 0x80;  /*  0x80 = removable  */
                        memcpy(xferp->data_in+16, "TAPE            ", 16);

                        if (machine->machine_type == MACHINE_PMAX) {
                                /*
                                 *  TODO:  find out if these are correct.
                                 *
                                 *  The name might be TZK10, TSZ07, or TLZ04,
                                 *  or something completely different.
                                 */
                                memcpy(xferp->data_in+8, "DEC     ", 8);
                                memcpy(xferp->data_in+16,
                                    "TK50     (C) DEC", 16);
                                memcpy(xferp->data_in+32, "2000", 4);
                        }
                }

                diskimage__return_default_status_and_message(xferp);
                break;

        case SCSIBLOCKCMD_READ_CAPACITY:
                debug("READ_CAPACITY");

                if (xferp->cmd_len != 10)
                        fatal(" [ weird READ_CAPACITY len=%i, should be 10 ] ",
                            xferp->cmd_len);
                else {
                        if (xferp->cmd[8] & 1) {
                                /*  Partial Medium Indicator bit...  TODO  */
                                fatal("WARNING: READ_CAPACITY with PMI bit"
                                    " set not yet implemented\n");
                        }
                }

                /*  Return data:  */
                scsi_transfer_allocbuf(&xferp->data_in_len, &xferp->data_in,
                    8, 1);

                diskimage_recalc_size(d);

                size = d->total_size / d->logical_block_size;
                if (d->total_size & (d->logical_block_size-1))
                        size ++;

                xferp->data_in[0] = (size >> 24) & 255;
                xferp->data_in[1] = (size >> 16) & 255;
                xferp->data_in[2] = (size >> 8) & 255;
                xferp->data_in[3] = size & 255;

                xferp->data_in[4] = (d->logical_block_size >> 24) & 255;
                xferp->data_in[5] = (d->logical_block_size >> 16) & 255;
                xferp->data_in[6] = (d->logical_block_size >> 8) & 255;
                xferp->data_in[7] = d->logical_block_size & 255;

                diskimage__return_default_status_and_message(xferp);
                break;

        case SCSICMD_MODE_SENSE:
        case SCSICMD_MODE_SENSE10:      
                debug("MODE_SENSE");
                q = 4; retlen = xferp->cmd[4];
                switch (xferp->cmd_len) {
                case 6: break;
                case 10:q = 8;
                        retlen = xferp->cmd[7] * 256 + xferp->cmd[8];
                        break;
                default:fatal(" (unimplemented mode_sense len=%i)",
                            xferp->cmd_len);
                }

                /*
                 *  NOTE/TODO: This code doesn't handle too short retlens
                 *  very well. A quick hack around this is that I allocate
                 *  a bit too much memory, so that nothing is actually
                 *  written outside of xferp->data_in[].
                 */

                retlen += 100;          /*  Should be enough. (Ugly.)  */

                if ((xferp->cmd[2] & 0xc0) != 0)
                        fatal("WARNING: mode sense, cmd[2] = 0x%02x\n",
                            xferp->cmd[2]);

                /*  Return data:  */
                scsi_transfer_allocbuf(&xferp->data_in_len,
                    &xferp->data_in, retlen, 1);

                xferp->data_in_len -= 100;      /*  Restore size.  */

                pagecode = xferp->cmd[2] & 0x3f;

                debug("[ MODE SENSE id %i, pagecode=%i ]\n", id, pagecode);

                /*  4 bytes of header for 6-byte command,
                    8 bytes of header for 10-byte command.  */
                xferp->data_in[0] = retlen;     /*  0: mode data length  */
                xferp->data_in[1] = d->is_a_cdrom? 0x05 : 0x00;
                                /*  1: medium type  */
                xferp->data_in[2] = 0x00;       /*  device specific
                                                    parameter  */
                xferp->data_in[3] = 8 * 1;      /*  block descriptor
                                                    length: 1 page (?)  */

                xferp->data_in[q+0] = 0x00;     /*  density code  */
                xferp->data_in[q+1] = 0;        /*  nr of blocks, high  */
                xferp->data_in[q+2] = 0;        /*  nr of blocks, mid  */
                xferp->data_in[q+3] = 0;        /*  nr of blocks, low */
                xferp->data_in[q+4] = 0x00;     /*  reserved  */
                xferp->data_in[q+5] = (d->logical_block_size >> 16) & 255;
                xferp->data_in[q+6] = (d->logical_block_size >> 8) & 255;
                xferp->data_in[q+7] = d->logical_block_size & 255;
                q += 8;

                diskimage__return_default_status_and_message(xferp);

                /*  descriptors, 8 bytes (each)  */

                /*  page, n bytes (each)  */
                switch (pagecode) {
                case 0:
                        /*  TODO: Nothing here?  */
                        break;
                case 1:         /*  read-write error recovery page  */
                        xferp->data_in[q + 0] = pagecode;
                        xferp->data_in[q + 1] = 10;
                        break;
                case 3:         /*  format device page  */
                        xferp->data_in[q + 0] = pagecode;
                        xferp->data_in[q + 1] = 22;

                        /*  10,11 = sectors per track  */
                        xferp->data_in[q + 10] = 0;
                        xferp->data_in[q + 11] = d->sectors_per_track;

                        /*  12,13 = physical sector size  */
                        xferp->data_in[q + 12] =
                            (d->logical_block_size >> 8) & 255;
                        xferp->data_in[q + 13] = d->logical_block_size & 255;
                        break;
                case 4:         /*  rigid disk geometry page  */
                        xferp->data_in[q + 0] = pagecode;
                        xferp->data_in[q + 1] = 22;
                        xferp->data_in[q + 2] = (d->ncyls >> 16) & 255;
                        xferp->data_in[q + 3] = (d->ncyls >> 8) & 255;
                        xferp->data_in[q + 4] = d->ncyls & 255;
                        xferp->data_in[q + 5] = d->heads;

                        xferp->data_in[q + 20] = (d->rpms >> 8) & 255;
                        xferp->data_in[q + 21] = d->rpms & 255;
                        break;
                case 5:         /*  flexible disk page  */
                        xferp->data_in[q + 0] = pagecode;
                        xferp->data_in[q + 1] = 0x1e;

                        /*  2,3 = transfer rate  */
                        xferp->data_in[q + 2] = ((5000) >> 8) & 255;
                        xferp->data_in[q + 3] = (5000) & 255;

                        xferp->data_in[q + 4] = d->heads;
                        xferp->data_in[q + 5] = d->sectors_per_track;

                        /*  6,7 = data bytes per sector  */
                        xferp->data_in[q + 6] = (d->logical_block_size >> 8)
                            & 255;
                        xferp->data_in[q + 7] = d->logical_block_size & 255;

                        xferp->data_in[q + 8] = (d->ncyls >> 8) & 255;
                        xferp->data_in[q + 9] = d->ncyls & 255;

                        xferp->data_in[q + 28] = (d->rpms >> 8) & 255;
                        xferp->data_in[q + 29] = d->rpms & 255;
                        break;
                default:
                        fatal("[ MODE_SENSE for page %i is not yet "
                            "implemented! ]\n", pagecode);
                }

                break;

        case SCSICMD_READ:
        case SCSICMD_READ_10:
                debug("READ");

                /*
                 *  For tape devices, read data at the current position.
                 *  For disk and CDROM devices, the command bytes contain
                 *  an offset telling us where to read from the device.
                 */

                if (d->is_a_tape) {
                        /*  bits 7..5 of cmd[1] are the LUN bits... TODO  */

                        size = (xferp->cmd[2] << 16) +
                               (xferp->cmd[3] <<  8) +
                                xferp->cmd[4];

                        /*  Bit 1 of cmd[1] is the SILI bit (TODO), and
                            bit 0 is the "use fixed length" bit.  */

                        if (xferp->cmd[1] & 0x01) {
                                /*  Fixed block length:  */
                                size *= d->logical_block_size;
                        }

                        if (d->filemark) {
                                /*  At end of file, switch to the next
                                    automagically:  */
                                d->tape_filenr ++;
                                diskimage__switch_tape(d);

                                d->filemark = 0;
                        }

                        ofs = d->tape_offset;

                        fatal("[ READ tape, id=%i file=%i, cmd[1]=%02x size=%i"
                            ", ofs=%lli ]\n", id, d->tape_filenr,
                            xferp->cmd[1], (int)size, (long long)ofs);
                } else {
                        if (xferp->cmd[0] == SCSICMD_READ) {
                                if (xferp->cmd_len != 6)
                                        debug(" (weird len=%i)",
                                            xferp->cmd_len);

                                /*
                                 *  bits 4..0 of cmd[1], and cmd[2] and cmd[3]
                                 *  hold the logical block address.
                                 *
                                 *  cmd[4] holds the number of logical blocks
                                 *  to transfer. (Special case if the value is
                                 *  0, actually means 256.)
                                 */
                                ofs = ((xferp->cmd[1] & 0x1f) << 16) +
                                      (xferp->cmd[2] << 8) + xferp->cmd[3];
                                retlen = xferp->cmd[4];
                                if (retlen == 0)
                                        retlen = 256;
                        } else {
                                if (xferp->cmd_len != 10)
                                        debug(" (weird len=%i)",
                                            xferp->cmd_len);

                                /*
                                 *  cmd[2..5] hold the logical block address.
                                 *  cmd[7..8] holds the number of logical
                                 *  blocks to transfer. (NOTE: If the value is
                                 *  0, this means 0, not 65536. :-)
                                 */
                                ofs = ((uint64_t)xferp->cmd[2] << 24) +
                                    (xferp->cmd[3] << 16) + (xferp->cmd[4] << 8)
                                    + xferp->cmd[5];
                                retlen = (xferp->cmd[7] << 8) + xferp->cmd[8];
                        }

                        size = retlen * d->logical_block_size;
                        ofs *= d->logical_block_size;
                }

                /*  Return data:  */
                scsi_transfer_allocbuf(&xferp->data_in_len, &xferp->data_in,
                    size, 0);

                debug(" READ  ofs=%lli size=%i\n", (long long)ofs, (int)size);

                diskimage__return_default_status_and_message(xferp);

                d->filemark = 0;

                /*
                 *  Failure? Then set check condition.
                 *  For tapes, error should only occur at the end of a file.
                 *
                 *  "If the logical unit encounters a filemark during
                 *   a READ command, CHECK CONDITION status shall be
                 *   returned and the filemark and valid bits shall be
                 *   set to one in the sense data. The sense key shall
                 *   be set to NO SENSE"..
                 */
                if (d->is_a_tape && d->f != NULL && feof(d->f)) {
                        debug(" feof id=%i\n", id);
                        xferp->status[0] = 0x02;        /*  CHECK CONDITION  */

                        d->filemark = 1;
                } else
                        diskimage__internal_access(d, 0, ofs,
                            xferp->data_in, size);

                if (d->is_a_tape && d->f != NULL)
                        d->tape_offset = ftello(d->f);

                /*  TODO: other errors?  */
                break;

        case SCSICMD_WRITE:
        case SCSICMD_WRITE_10:
                debug("WRITE");

                /*  TODO: tape  */

                if (xferp->cmd[0] == SCSICMD_WRITE) {
                        if (xferp->cmd_len != 6)
                                debug(" (weird len=%i)", xferp->cmd_len);

                        /*
                         *  bits 4..0 of cmd[1], and cmd[2] and cmd[3] hold the
                         *  logical block address.
                         *
                         *  cmd[4] holds the number of logical blocks to
                         *  transfer. (Special case if the value is 0, actually
                         *  means 256.)
                         */
                        ofs = ((xferp->cmd[1] & 0x1f) << 16) +
                              (xferp->cmd[2] << 8) + xferp->cmd[3];
                        retlen = xferp->cmd[4];
                        if (retlen == 0)
                                retlen = 256;
                } else {
                        if (xferp->cmd_len != 10)
                                debug(" (weird len=%i)", xferp->cmd_len);

                        /*
                         *  cmd[2..5] hold the logical block address.
                         *  cmd[7..8] holds the number of logical blocks to
                         *  transfer. (NOTE: If the value is 0 this means 0,
                         *  not 65536.)
                         */
                        ofs = ((uint64_t)xferp->cmd[2] << 24) +
                            (xferp->cmd[3] << 16) + (xferp->cmd[4] << 8) +
                            xferp->cmd[5];
                        retlen = (xferp->cmd[7] << 8) + xferp->cmd[8];
                }

                size = retlen * d->logical_block_size;
                ofs *= d->logical_block_size;

                if (xferp->data_out_offset != size) {
                        debug(", data_out == NULL, wanting %i bytes, \n\n",
                            (int)size);
                        xferp->data_out_len = size;
                        return 2;
                }

                debug(", data_out != NULL, OK :-)");

                debug("WRITE ofs=%i size=%i offset=%i\n", (int)ofs,
                    (int)size, (int)xferp->data_out_offset);

                diskimage__internal_access(d, 1, ofs,
                    xferp->data_out, size);

                /*  TODO: how about return code?  */

                /*  Is this really necessary?  */
                /*  fsync(fileno(d->f));  */

                diskimage__return_default_status_and_message(xferp);
                break;

        case SCSICMD_SYNCHRONIZE_CACHE:
                debug("SYNCHRONIZE_CACHE");

                if (xferp->cmd_len != 10)
                        debug(" (weird len=%i)", xferp->cmd_len);

                /*  TODO: actualy care about cmd[]  */
                fsync(fileno(d->f));

                diskimage__return_default_status_and_message(xferp);
                break;

        case SCSICMD_START_STOP_UNIT:
                debug("START_STOP_UNIT");

                if (xferp->cmd_len != 6)
                        debug(" (weird len=%i)", xferp->cmd_len);

                for (i=0; i<(ssize_t)xferp->cmd_len; i++)
                        debug(" %02x", xferp->cmd[i]);

                /*  TODO: actualy care about cmd[]  */

                diskimage__return_default_status_and_message(xferp);
                break;

        case SCSICMD_REQUEST_SENSE:
                debug("REQUEST_SENSE");

                retlen = xferp->cmd[4];

                /*  TODO: bits 765 of buf[1] contains the LUN  */
                if (xferp->cmd[1] != 0x00)
                        fatal("WARNING: REQUEST_SENSE with cmd[1]=0x%02x not"
                            " yet implemented\n", (int)xferp->cmd[1]);

                if (retlen < 18) {
                        fatal("WARNING: SCSI request sense len=%i, <18!\n",
                            (int)retlen);
                        retlen = 18;
                }

                /*  Return data:  */
                scsi_transfer_allocbuf(&xferp->data_in_len, &xferp->data_in,
                    retlen, 1);

                xferp->data_in[0] = 0x80 + 0x70;/*  0x80 = valid,
                                                    0x70 = "current errors"  */
                xferp->data_in[2] = 0x00;       /*  SENSE KEY!  */

                if (d->filemark) {
                        xferp->data_in[2] = 0x80;
                }
                debug(": [2]=0x%02x ", xferp->data_in[2]);

                printf(" XXX(!) \n");

                /*  TODO  */
                xferp->data_in[7] = retlen - 7; /*  additional sense length  */
                /*  TODO  */

                diskimage__return_default_status_and_message(xferp);
                break;

        case SCSICMD_READ_BLOCK_LIMITS:
                debug("READ_BLOCK_LIMITS");

                retlen = 6;

                /*  TODO: bits 765 of buf[1] contains the LUN  */
                if (xferp->cmd[1] != 0x00)
                        fatal("WARNING: READ_BLOCK_LIMITS with cmd[1]="
                            "0x%02x not yet implemented\n", (int)xferp->cmd[1]);

                /*  Return data:  */
                scsi_transfer_allocbuf(&xferp->data_in_len, &xferp->data_in,
                    retlen, 1);

                /*
                 *  data[0] is reserved, data[1..3] contain the maximum block
                 *  length limit, data[4..5] contain the minimum limit.
                 */

                {
                        int max_limit = 32768;
                        int min_limit = 128;

                        xferp->data_in[1] = (max_limit >> 16) & 255;
                        xferp->data_in[2] = (max_limit >>  8) & 255;
                        xferp->data_in[3] =  max_limit        & 255;
                        xferp->data_in[4] = (min_limit >>  8) & 255;
                        xferp->data_in[5] =  min_limit        & 255;
                }

                diskimage__return_default_status_and_message(xferp);
                break;

        case SCSICMD_REWIND:
                debug("REWIND");

                /*  TODO: bits 765 of buf[1] contains the LUN  */
                if ((xferp->cmd[1] & 0xe0) != 0x00)
                        fatal("WARNING: REWIND with cmd[1]=0x%02x not yet "
                            "implemented\n", (int)xferp->cmd[1]);

                /*  Close and reopen.  */

                if (d->f != NULL)
                        fclose(d->f);

                d->f = fopen(d->fname, d->writable? "r+" : "r");
                if (d->f == NULL) {
                        fprintf(stderr, "[ diskimage: could not (re)open "
                            "'%s' ]\n", d->fname);
                        /*  TODO: return error  */
                }

                d->tape_offset = 0;
                d->tape_filenr = 0;
                d->filemark = 0;

                diskimage__return_default_status_and_message(xferp);
                break;

        case SCSICMD_SPACE:
                debug("SPACE");

                /*  TODO: bits 765 of buf[1] contains the LUN  */
                if ((xferp->cmd[1] & 0xe0) != 0x00)
                        fatal("WARNING: SPACE with cmd[1]=0x%02x not yet "
                            "implemented\n", (int)xferp->cmd[1]);

                /*
                 *  Bits 2..0 of buf[1] contain the 'code' which describes how
                 *  we should space, and buf[2..4] contain the number of
                 *  operations.
                 */
                debug("[ SPACE: buf[] = %02x %02x %02x %02x %02x %02x ]\n",
                    xferp->cmd[0],
                    xferp->cmd[1],
                    xferp->cmd[2],
                    xferp->cmd[3],
                    xferp->cmd[4],
                    xferp->cmd[5]);

                switch (xferp->cmd[1] & 7) {
                case 1: /*  Seek to a different file nr:  */
                        {
                                int diff = (xferp->cmd[2] << 16) +
                                    (xferp->cmd[3] << 8) + xferp->cmd[4];

                                /*  Negative seek offset:  */
                                if (diff & (1 << 23))
                                        diff = - (16777216 - diff);

                                d->tape_filenr += diff;
                        }

                        /*  At end of file, switch to the next tape file:  */
                        if (d->filemark) {
                                d->tape_filenr ++;
                                d->filemark = 0;
                        }

                        debug("{ switching to tape file %i }", d->tape_filenr);
                        diskimage__switch_tape(d);
                        d->filemark = 0;
                        break;
                default:
                        fatal("[ diskimage.c: unimplemented SPACE type %i ]\n",
                            xferp->cmd[1] & 7);
                }

                diskimage__return_default_status_and_message(xferp);
                break;

        case SCSICDROM_READ_SUBCHANNEL:
                /*
                 *  According to
                 *  http://mail-index.netbsd.org/port-i386/1997/03/03/0010.html:
                 *
                 *  "The READ_CD_CAPACITY, READ_SUBCHANNEL, and MODE_SELECT
                 *   commands have the same opcode in SCSI or ATAPI, but don't
                 *   have the same command structure"...
                 *
                 *  TODO: This still doesn't work. Hm.
                 */
                retlen = 48;

                debug("CDROM_READ_SUBCHANNEL/READ_CD_CAPACITY, cmd[1]=0x%02x",
                    xferp->cmd[1]);

                /*  Return data:  */
                scsi_transfer_allocbuf(&xferp->data_in_len,
                    &xferp->data_in, retlen, 1);

                diskimage_recalc_size(d);

                size = d->total_size / d->logical_block_size;
                if (d->total_size & (d->logical_block_size-1))
                        size ++;

                xferp->data_in[0] = (size >> 24) & 255;
                xferp->data_in[1] = (size >> 16) & 255;
                xferp->data_in[2] = (size >> 8) & 255;
                xferp->data_in[3] = size & 255;

                xferp->data_in[4] = (d->logical_block_size >> 24) & 255;
                xferp->data_in[5] = (d->logical_block_size >> 16) & 255;
                xferp->data_in[6] = (d->logical_block_size >> 8) & 255;
                xferp->data_in[7] = d->logical_block_size & 255;

                diskimage__return_default_status_and_message(xferp);
                break;

        case SCSICDROM_READ_TOC:
                debug("(CDROM_READ_TOC: ");
                debug("lun=%i msf=%i ",
                    xferp->cmd[1] >> 5, (xferp->cmd[1] >> 1) & 1);
                debug("starting_track=%i ", xferp->cmd[6]);
                retlen = xferp->cmd[7] * 256 + xferp->cmd[8];
                debug("allocation_len=%i)\n", retlen);

                /*  Return data:  */
                scsi_transfer_allocbuf(&xferp->data_in_len,
                    &xferp->data_in, retlen, 1);

                xferp->data_in[0] = 0;
                xferp->data_in[1] = 10;
                xferp->data_in[2] = 0;          /*  First track.  */
                xferp->data_in[3] = 0;          /*  Last track.  */

                /*  Track 0 data:  */
                xferp->data_in[4] = 0x00;       /*  Reserved.  */
                xferp->data_in[5] = 0x04;       /*  ADR + CTRL:
                                                    Data, not audio  */
                xferp->data_in[6] = 0x00;       /*  Track nr  */
                xferp->data_in[7] = 0x00;       /*  Reserved  */
                /*  8..11 = absolute CDROM address  */

                diskimage__return_default_status_and_message(xferp);
                break;

        case SCSICMD_MODE_SELECT:
                debug("[ SCSI MODE_SELECT: ");

                /*
                 *  TODO:
                 *
                 *  This is super-hardcoded for NetBSD's usage of mode_select
                 *  to set the size of CDROM sectors to 2048.
                 */

                if (xferp->data_out_offset == 0) {
                        xferp->data_out_len = 12;       /*  TODO  */
                        debug("data_out == NULL, wanting %i bytes ]\n",
                            (int)xferp->data_out_len);
                        return 2;
                }

                debug("data_out!=NULL (OK), ");

                /*  TODO:  Care about cmd?  */

                /*  Set sector size to 2048:  */
                /*  00 05 00 08 00 03 ca 40 00 00 08 00  */
                if (xferp->data_out[0] == 0x00 &&
                    xferp->data_out[1] == 0x05 &&
                    xferp->data_out[2] == 0x00 &&
                    xferp->data_out[3] == 0x08) {
                        d->logical_block_size =
                            (xferp->data_out[9] << 16) +
                            (xferp->data_out[10] << 8) +
                            xferp->data_out[11];
                        debug("[ setting logical_block_size to %i ]\n",
                            d->logical_block_size);
                } else {
                        int i;
                        fatal("[ unknown MODE_SELECT: cmd =");
                        for (i=0; i<(ssize_t)xferp->cmd_len; i++)
                                fatal(" %02x", xferp->cmd[i]);
                        fatal(", data_out =");
                        for (i=0; i<(ssize_t)xferp->data_out_len; i++)
                                fatal(" %02x", xferp->data_out[i]);
                        fatal(" ]");
                }

                debug(" ]\n");
                diskimage__return_default_status_and_message(xferp);
                break;

        case SCSICMD_PREVENT_ALLOW_REMOVE:
                debug("[ SCSI 0x%02x Prevent/allow medium removal: "
                    "TODO ]\n", xferp->cmd[0]);

                diskimage__return_default_status_and_message(xferp);
                break;

        case 0xbd:
                fatal("[ SCSI 0x%02x (len %i), TODO: ", xferp->cmd[0],
                    xferp->cmd_len);
                for (i=0; i<(ssize_t)xferp->cmd_len; i++)
                        fatal(" %02x", xferp->cmd[i]);
                fatal(" ]\n");

                /*
                 *  Used by Windows NT?
                 *
                 *  Not documented in http://www.danbbs.dk/~dino/
                 *              SCSI/SCSI2-D.html.
                 *  Google gave the answer "MECHANISM_STATUS" for ATAPI. Hm.
                 */

                if (xferp->cmd_len < 12) {
                        fatal("WEIRD LEN?\n");
                        retlen = 8;
                } else {
                        retlen = xferp->cmd[8] * 256 + xferp->cmd[9];
                }

                /*  Return data:  */
                scsi_transfer_allocbuf(&xferp->data_in_len,
                    &xferp->data_in, retlen, 1);

                diskimage__return_default_status_and_message(xferp);

                break;

        default:
                fatal("[ UNIMPLEMENTED SCSI command 0x%02x, disk id=%i ]\n",
                    xferp->cmd[0], id);
                exit(1);
        }
        debug(" ]\n");

        return 1;
}


/*
 *  diskimage_access():
 *
 *  Read from or write to a disk image on a machine.
 *
 *  Returns 1 if the access completed successfully, 0 otherwise.
 */
int diskimage_access(struct machine *machine, int id, int type, int writeflag,
        off_t offset, unsigned char *buf, size_t len)
{
        struct diskimage *d = machine->first_diskimage;

        while (d != NULL) {
                if (d->type == type && d->id == id)
                        break;
                d = d->next;
        }

        if (d == NULL) {
                fatal("[ diskimage_access(): ERROR: trying to access a "
                    "non-existant %s disk image (id %i)\n",
                    diskimage_types[type], id);
                return 0;
        }

        return diskimage__internal_access(d, writeflag, offset, buf, len);
}


/*
 *  diskimage_add():
 *
 *  Add a disk image.  fname is the filename of the disk image.
 *  The filename may be prefixed with one or more modifiers, followed
 *  by a colon.
 *
 *      b       specifies that this is a bootable device
 *      c       CD-ROM (instead of a normal DISK)
 *      d       DISK (this is the default)
 *      f       FLOPPY (instead of SCSI)
 *      gH;S;   set geometry (H=heads, S=sectors per track, cylinders are
 *              automatically calculated). (This is ignored for floppies.)
 *      i       IDE (instead of SCSI)
 *      r       read-only (don't allow changes to the file)
 *      s       SCSI (this is the default)
 *      t       tape
 *      0-7     force a specific SCSI ID number
 *
 *  machine is assumed to be non-NULL.
 *  Returns an integer >= 0 identifying the disk image.
 */
int diskimage_add(struct machine *machine, char *fname)
{
        struct diskimage *d, *d2;
        int id = 0, override_heads=0, override_spt=0;
        int64_t bytespercyl;
        char *cp;
        int prefix_b=0, prefix_c=0, prefix_d=0, prefix_f=0, prefix_g=0;
        int prefix_i=0, prefix_r=0, prefix_s=0, prefix_t=0, prefix_id = -1;

        if (fname == NULL) {
                fprintf(stderr, "diskimage_add(): NULL ptr\n");
                return 0;
        }

        /*  Get prefix from fname:  */
        cp = strchr(fname, ':');
        if (cp != NULL) {
                while (fname <= cp) {
                        char c = *fname++;
                        switch (c) {
                        case '0':
                        case '1':
                        case '2':
                        case '3':
                        case '4':
                        case '5':
                        case '6':
                        case '7':
                                prefix_id = c - '0';
                                break;
                        case 'b':
                                prefix_b = 1;
                                break;
                        case 'c':
                                prefix_c = 1;
                                break;
                        case 'd':
                                prefix_d = 1;
                                break;
                        case 'f':
                                prefix_f = 1;
                                break;
                        case 'g':
                                prefix_g = 1;
                                override_heads = atoi(fname);
                                while (*fname != '\0' && *fname != ';')
                                        fname ++;
                                if (*fname == ';')
                                        fname ++;
                                override_spt = atoi(fname);
                                while (*fname != '\0' && *fname != ';' &&
                                    *fname != ':')
                                        fname ++;
                                if (*fname == ';')
                                        fname ++;
                                if (override_heads < 1 ||
                                    override_spt < 1) {
                                        fatal("Bad geometry: heads=%i "
                                            "spt=%i\n", override_heads,
                                            override_spt);
                                        exit(1);
                                }
                                break;
                        case 'i':
                                prefix_i = 1;
                                break;
                        case 'r':
                                prefix_r = 1;
                                break;
                        case 's':
                                prefix_s = 1;
                                break;
                        case 't':
                                prefix_t = 1;
                                break;
                        case ':':
                                break;
                        default:
                                fprintf(stderr, "diskimage_add(): invalid "
                                    "prefix char '%c'\n", c);
                                exit(1);
                        }
                }
        }

        /*  Allocate a new diskimage struct:  */
        d = malloc(sizeof(struct diskimage));
        if (d == NULL) {
                fprintf(stderr, "out of memory in diskimage_add()\n");
                exit(1);
        }
        memset(d, 0, sizeof(struct diskimage));

        d2 = machine->first_diskimage;
        if (d2 == NULL) {
                machine->first_diskimage = d;
        } else {
                while (d2->next != NULL)
                        d2 = d2->next;
                d2->next = d;
        }

        /*  Default to IDE disks...  */
        d->type = DISKIMAGE_IDE;

        /*  ... but some machines use SCSI by default:  */
        if (machine->machine_type == MACHINE_PMAX ||
            machine->machine_type == MACHINE_ARC)
                d->type = DISKIMAGE_SCSI;

        if (prefix_i + prefix_f + prefix_s > 1) {
                fprintf(stderr, "Invalid disk image prefix(es). You can"
                    "only use one of i, f, and s\nfor each disk image.\n");
                exit(1);
        }

        if (prefix_i)
                d->type = DISKIMAGE_IDE;
        if (prefix_f)
                d->type = DISKIMAGE_FLOPPY;
        if (prefix_s)
                d->type = DISKIMAGE_SCSI;

        d->fname = strdup(fname);
        if (d->fname == NULL) {
                fprintf(stderr, "out of memory\n");
                exit(1);
        }

        d->logical_block_size = 512;

        /*
         *  Is this a tape, CD-ROM or a normal disk?
         *
         *  An intelligent guess, if no prefixes are used, would be that
         *  filenames ending with .iso or .cdr are CD-ROM images.
         */
        if (prefix_t) {
                d->is_a_tape = 1;
        } else {
                if (prefix_c ||
                    ((strlen(d->fname) > 4 &&
                    (strcasecmp(d->fname + strlen(d->fname) - 4, ".cdr") == 0 ||
                    strcasecmp(d->fname + strlen(d->fname) - 4, ".iso") == 0))
                    && !prefix_d)
                   ) {
                        d->is_a_cdrom = 1;

                        /*
                         *  This is tricky. Should I use 512 or 2048 here?
                         *  NetBSD/pmax 1.6.2 and Ultrix likes 512 bytes
                         *  per sector, but NetBSD 2.0_BETA suddenly ignores
                         *  this value and uses 2048 instead.
                         *
                         *  OpenBSD/arc doesn't like 2048, it requires 512
                         *  to work correctly.
                         *
                         *  TODO
                         */

#if 0
                        if (machine->machine_type == MACHINE_PMAX)
                                d->logical_block_size = 512;
                        else
                                d->logical_block_size = 2048;
#endif
                        d->logical_block_size = 512;
                }
        }

        diskimage_recalc_size(d);

        if ((d->total_size == 720*1024 || d->total_size == 1474560
            || d->total_size == 2949120 || d->total_size == 1228800)
            && !prefix_i && !prefix_s)
                d->type = DISKIMAGE_FLOPPY;

        switch (d->type) {
        case DISKIMAGE_FLOPPY:
                if (d->total_size < 737280) {
                        fatal("\nTODO: small (non-80-cylinder) floppies?\n\n");
                        exit(1);
                }
                d->cylinders = 80;
                d->heads = 2;
                d->sectors_per_track = d->total_size / (d->cylinders *
                    d->heads * 512);
                break;
        default:/*  Non-floppies:  */
                d->heads = 16;
                d->sectors_per_track = 63;
                if (prefix_g) {
                        d->chs_override = 1;
                        d->heads = override_heads;
                        d->sectors_per_track = override_spt;
                }
                bytespercyl = d->heads * d->sectors_per_track * 512;
                d->cylinders = d->total_size / bytespercyl;
                if (d->cylinders * bytespercyl < d->total_size)
                        d->cylinders ++;
        }

        d->rpms = 3600;

        if (prefix_b)
                d->is_boot_device = 1;

        d->writable = access(fname, W_OK) == 0? 1 : 0;

        if (d->is_a_cdrom || prefix_r)
                d->writable = 0;

        d->f = fopen(fname, d->writable? "r+" : "r");
        if (d->f == NULL) {
                perror(fname);
                exit(1);
        }

        /*  Calculate which ID to use:  */
        if (prefix_id == -1) {
                int free = 0, collision = 1;

                while (collision) {
                        collision = 0;
                        d2 = machine->first_diskimage;
                        while (d2 != NULL) {
                                /*  (don't compare against ourselves :)  */
                                if (d2 == d) {
                                        d2 = d2->next;
                                        continue;
                                }
                                if (d2->id == free && d2->type == d->type) {
                                        collision = 1;
                                        break;
                                }
                                d2 = d2->next;
                        }
                        if (!collision)
                                id = free;
                        else
                                free ++;
                }
        } else {
                id = prefix_id;
                d2 = machine->first_diskimage;
                while (d2 != NULL) {
                        /*  (don't compare against ourselves :)  */
                        if (d2 == d) {
                                d2 = d2->next;
                                continue;
                        }
                        if (d2->id == id && d2->type == d->type) {
                                fprintf(stderr, "disk image id %i "
                                    "already in use\n", id);
                                exit(1);
                        }
                        d2 = d2->next;
                }
        }

        d->id = id;

        return id;
}


/*
 *  diskimage_bootdev():
 *
 *  Returns the disk id of the device which we're booting from.  If typep is
 *  non-NULL, the type is returned as well.
 *
 *  If no disk was used as boot device, then -1 is returned. (In practice,
 *  this is used to fake network (tftp) boot.)
 */
int diskimage_bootdev(struct machine *machine, int *typep)
{
        struct diskimage *d;

        d = machine->first_diskimage;
        while (d != NULL) {
                if (d->is_boot_device) {
                        if (typep != NULL)
                                *typep = d->type;
                        return d->id;
                }
                d = d->next;
        }

        d = machine->first_diskimage;
        if (d != NULL) {
                if (typep != NULL)
                        *typep = d->type;
                return d->id;
        }

        return -1;
}


/*
 *  diskimage_getname():
 *
 *  Returns 1 if a valid disk image name was returned, 0 otherwise.
 */
int diskimage_getname(struct machine *machine, int id, int type,
        char *buf, size_t bufsize)
{
        struct diskimage *d = machine->first_diskimage;

        if (buf == NULL)
                return 0;

        while (d != NULL) {
                if (d->type == type && d->id == id) {
                        char *p = strrchr(d->fname, '/');
                        if (p == NULL)
                                p = d->fname;
                        else
                                p ++;
                        snprintf(buf, bufsize, "%s", p);
                        return 1;
                }
                d = d->next;
        }
        return 0;
}


/*
 *  diskimage_is_a_cdrom():
 *
 *  Returns 1 if a disk image is a CDROM, 0 otherwise.
 */
int diskimage_is_a_cdrom(struct machine *machine, int id, int type)
{
        struct diskimage *d = machine->first_diskimage;

        while (d != NULL) {
                if (d->type == type && d->id == id)
                        return d->is_a_cdrom;
                d = d->next;
        }
        return 0;
}


/*
 *  diskimage_is_a_tape():
 *
 *  Returns 1 if a disk image is a tape, 0 otherwise.
 *
 *  (Used in src/machine.c, to select 'rz' vs 'tz' for DECstation
 *  boot strings.)
 */
int diskimage_is_a_tape(struct machine *machine, int id, int type)
{
        struct diskimage *d = machine->first_diskimage;

        while (d != NULL) {
                if (d->type == type && d->id == id)
                        return d->is_a_tape;
                d = d->next;
        }
        return 0;
}


/*
 *  diskimage_dump_info():
 *
 *  Debug dump of all diskimages that are loaded for a specific machine.
 */
void diskimage_dump_info(struct machine *machine)
{
        int iadd = DEBUG_INDENTATION;
        struct diskimage *d = machine->first_diskimage;

        while (d != NULL) {
                debug("diskimage: %s\n", d->fname);
                debug_indentation(iadd);

                switch (d->type) {
                case DISKIMAGE_SCSI:
                        debug("SCSI");
                        break;
                case DISKIMAGE_IDE:
                        debug("IDE");
                        break;
                case DISKIMAGE_FLOPPY:
                        debug("FLOPPY");
                        break;
                default:
                        debug("UNKNOWN type %i", d->type);
                }

                debug(" %s", d->is_a_tape? "TAPE" :
                        (d->is_a_cdrom? "CD-ROM" : "DISK"));
                debug(" id %i, ", d->id);
                debug("%s, ", d->writable? "read/write" : "read-only");

                if (d->type == DISKIMAGE_FLOPPY)
                        debug("%lli KB", (long long) (d->total_size / 1024));
                else
                        debug("%lli MB", (long long) (d->total_size / 1048576));

                if (d->type == DISKIMAGE_FLOPPY || d->chs_override)
                        debug(" (CHS=%i,%i,%i)", d->cylinders, d->heads,
                            d->sectors_per_track);
                else
                        debug(" (%lli sectors)", (long long)
                           (d->total_size / 512));

                if (d->is_boot_device)
                        debug(" (BOOT)");
                debug("\n");

                debug_indentation(-iadd);

                d = d->next;
        }
}
