topology: Define a free handler for the element

This handler is defined for type-specific destruction of an element.

Signed-off-by: Mengdong Lin <mengdong.lin@linux.intel.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

src/topology/elem.c

@@ -83,8 +83,12 @@ void tplg_elem_free(struct tplg_elem *elem)
 	/* free struct snd_tplg_ object,
 	 * the union pointers share the same address
 	 */
-	if (elem->obj)
+	if (elem->obj) {
+		if (elem->free)
+			elem->free(elem->obj);
+
 		free(elem->obj);
+	}
 
 	free(elem);
 }

src/topology/tplg_local.h

@@ -127,6 +127,8 @@ struct tplg_elem {
 	 */
 	struct list_head ref_list;
 	struct list_head list; /* list of all elements with same type */
+
+	void (*free)(void *obj);
 };
 
 struct map_elem {