# File lib/vagrant-libvirt/config.rb, line 466
      def usb(options = {})
        if (options[:bus].nil? || options[:device].nil?) && options[:vendor].nil? && options[:product].nil?
          raise 'Bus and device and/or vendor and/or product must be specified. Check `lsusb` for these.'
        end

        @usbs = [] if @usbs == UNSET_VALUE

        @usbs.push(bus:           options[:bus],
                   device:        options[:device],
                   vendor:        options[:vendor],
                   product:       options[:product],
                   startupPolicy: options[:startupPolicy])
      end