static int can_read(struct v4l2_loopback_device *dev, struct v4l2_loopback_opener *opener)
{
	int ret;

	spin_lock_bh(&dev->lock);
	check_timers(dev);
	ret = dev->write_position > opener->read_position
		|| dev->reread_count > opener->reread_count
		|| dev->timeout_happened;
	spin_unlock_bh(&dev->lock);
	return ret;
}