+/**
+ * snd_card_unref - release the reference counter
+ * @card: the card instance
+ *
+ * Decrements the reference counter. When it reaches to zero, wake up
+ * the sleeper and call the destructor if needed.
+ */
+void snd_card_unref(struct snd_card *card)
+{
+ if (atomic_dec_and_test(&card->refcount)) {
+ wake_up(&card->shutdown_sleep);
+ if (card->free_on_last_close)
+ snd_card_do_free(card);
+ }
+}
+EXPORT_SYMBOL(snd_card_unref);
+