Miscellany

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;}