static int acm_alloc_minor(struct acm *acm)
{
	int minor;

	mutex_lock(&acm_minors_lock);
	minor = idr_alloc(&acm_minors, acm, 0, ACM_TTY_MINORS, GFP_KERNEL);
	mutex_unlock(&acm_minors_lock);

	return minor;
}

Unknown