static int vidioc_s_output(struct file *file, void *fh, unsigned int i)
{
	struct v4l2_loopback_device *dev = v4l2loopback_getdevice(file);
        if (!dev->announce_all_caps && !dev->ready_for_output)
		return -ENOTTY;

	if (i)
		return -EINVAL;

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

	if (i)
		return -EINVAL;

	return 0;
}