ASoC: Define add/remove_dai_link ops for a soc card

A machine driver can register the two ops.

When a DAI link is added or removed by a component's topology, the
ASoC core can call the ops to notify the machine driver for extra
intialization or destruction.

E.g. topology can create FE DAI links from a cpu DAI component, and
the machine driver may define an add_dai_link ops to set machine-specific
.init ops for the DAI link.
Signed-off-by: Mengdong Lin <mengdong.lin@linux.intel.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

include/sound/soc.h

@@ -1104,6 +1104,11 @@ struct snd_soc_card {
 				   struct snd_soc_dapm_context *dapm,
 				   enum snd_soc_bias_level level);
 
+	int (*add_dai_link)(struct snd_soc_card *,
+			    struct snd_soc_dai_link *link);
+	void (*remove_dai_link)(struct snd_soc_card *,
+			    struct snd_soc_dai_link *link);
+
 	long pmdown_time;
 
 	/* CPU <--> Codec DAI links  */

sound/soc/soc-core.c

@@ -1260,6 +1260,12 @@ int snd_soc_add_dai_link(struct snd_soc_card *card,
 	}
 
 	lockdep_assert_held(&client_mutex);
+	/* Notify the machine driver for extra initialization
+	 * on the link created by topology.
+	 */
+	if (dai_link->dobj.type && card->add_dai_link)
+		card->add_dai_link(card, dai_link);
+
 	list_add_tail(&dai_link->list, &card->dai_link_list);
 	card->num_dai_links++;
 
@@ -1290,6 +1296,12 @@ void snd_soc_remove_dai_link(struct snd_soc_card *card,
 	}
 
 	lockdep_assert_held(&client_mutex);
+	/* Notify the machine driver for extra destruction
+	 * on the link created by topology.
+	 */
+	if (dai_link->dobj.type && card->remove_dai_link)
+		card->remove_dai_link(card, dai_link);
+
 	list_for_each_entry_safe(link, _link, &card->dai_link_list, list) {
 		if (link == dai_link) {
 			list_del(&link->list);