code: func parseLinuxDevice(device string) (container.DeviceMapping, error) {
  	src := ""
  	dst := ""
  	permissions := "rwm"
  	arr := strings.Split(device, ":")
  	switch len(arr) {
  	case 3:
  		permissions = arr[2]
  		fallthrough
  	case 2:
  		if validDeviceMode(arr[1]) {
  			permissions = arr[1]
  		} else {
  			dst = arr[1]
  		}
  		fallthrough
  	case 1:
  		src = arr[0]
  	default:
  		return container.DeviceMapping{}, errors.Errorf("invalid device specification: %s", device)
  	}
  
  	if dst == "" {
  		dst = src
  	}
  
  	deviceMapping := container.DeviceMapping{
  		PathOnHost:        src,
  		PathInContainer:   dst,
  		CgroupPermissions: permissions,
  	}
  	return deviceMapping, nil
  }
docs: // parseLinuxDevice parses a device mapping string to a container.DeviceMapping struct
  // knowing that the target is a Linux daemon