SCSI_CDROM_MAJOR
unregister_blkdev(SCSI_CDROM_MAJOR, "sr");
disk->major = SCSI_CDROM_MAJOR;
MODULE_ALIAS_BLOCKDEV_MAJOR(SCSI_CDROM_MAJOR);
rc = register_blkdev(SCSI_CDROM_MAJOR, "sr");
unregister_blkdev(SCSI_CDROM_MAJOR, "sr");