static int vidioc_s_input(struct file *file, void *fh, unsigned int i)
{
	struct v4l2_loopback_device *dev = v4l2loopback_getdevice(file);
	if (!dev->announce_all_caps && !dev->ready_for_capture)
		return -ENOTTY;
	if (i == 0)
		return 0;
	return -EINVAL;
}