def default_root_device_name(self, instance, image_meta, root_bdm):
    disk_bus = blockinfo.get_disk_bus_for_device_type(CONF.libvirt.virt_type, image_meta, 'disk')
    cdrom_bus = blockinfo.get_disk_bus_for_device_type(CONF.libvirt.virt_type, image_meta, 'cdrom')
    root_info = blockinfo.get_root_info(CONF.libvirt.virt_type, image_meta, root_bdm, disk_bus, cdrom_bus)
    return block_device.prepend_dev(root_info['dev'])
def default_root_device_name(self, instance, image_meta, root_bdm):
    disk_bus = blockinfo.get_disk_bus_for_device_type(CONF.libvirt.virt_type, image_meta, 'disk')
    cdrom_bus = blockinfo.get_disk_bus_for_device_type(CONF.libvirt.virt_type, image_meta, 'cdrom')
    root_info = blockinfo.get_root_info(CONF.libvirt.virt_type, image_meta, root_bdm, disk_bus, cdrom_bus)
    return block_device.prepend_dev(root_info['dev'])