static __poll_t snd_ctl_poll(struct file *file, poll_table * wait)
{
	__poll_t mask;
	struct snd_ctl_file *ctl;

	ctl = file->private_data;
	if (!ctl->subscribed)
		return 0;
	poll_wait(file, &ctl->change_sleep, wait);

	mask = 0;
	if (!list_empty(&ctl->events))
		mask |= EPOLLIN | EPOLLRDNORM;

	return mask;
}