int int13_retry(const com32sys_t *inreg, com32sys_t *outreg)
{
  int retry = 6;		/* Number of retries */
  com32sys_t tmpregs;

  memset(&tmpregs, 0, sizeof(tmpregs));
  if ( !outreg ) outreg = &tmpregs;

  while ( retry-- ) {
    __intcall(0x13, inreg, outreg);
    if ( !(outreg->eflags.l & EFLAGS_CF) ) {
      return 0;			/* CF=0, OK */
    }
  }
  return -1;			/* Error */
}

int syslinux_read_disk(diskinfo* disk_info, void *buf, uint32_t sector, uint16_t count)
{
  com32sys_t inreg;
  int status;
  void* bounce_buf;

  if (!count) {
     return 0;
  }

  memset(&inreg, 0, sizeof inreg);

  if ( disk_info->ebios ) {
    ebios_dapa *dapa = (struct ebios_dapa*)__com32.cs_bounce;
    bounce_buf = (char*)__com32.cs_bounce + SECTOR_SIZE;
    dapa->len = sizeof(*dapa);
    dapa->count = count;
    dapa->off = OFFS(bounce_buf);
    dapa->seg = SEG(bounce_buf);
    dapa->lba = sector;

    inreg.esi.w[0] = OFFS(dapa);
    inreg.ds       = SEG(dapa);
    inreg.edx.b[0] = disk_info->disk;
    inreg.eax.b[1] = 0x42;	/* Extended read */
  } else {
    unsigned int c, h, s, t;
    bounce_buf = __com32.cs_bounce;
    if ( !disk_info->cbios ) {
      /* We failed to get the geometry */
      if ( sector )
        return -1;		/* Can only read MBR */
      s = 1;  h = 0;  c = 0;
    } else {
      s = (sector % disk_info->sect) + 1;
      t = sector / disk_info->sect;	/* Track = head*cyl */
      h = t % disk_info->head;
      c = t / disk_info->head;
    }
    if ( s > 63 || h > 256 || c > 1023 )
      return -1;

    inreg.eax.b[1] = 0x02;	/* Read sector(s) into memory */
    inreg.eax.b[0] = count;
    inreg.ecx.b[1] = c & 0xff;
    inreg.ecx.b[0] = s + (c >> 6);
    inreg.edx.b[1] = h;
    inreg.edx.b[0] = disk_info->disk;
    inreg.ebx.w[0] = OFFS(bounce_buf);
    inreg.es       = SEG(bounce_buf);
  }
  status = int13_retry(&inreg, NULL);
  if (status == 0) {
     memcpy(buf, bounce_buf, count*SECTOR_SIZE);
  }
  return status;
}