sorcery: Add ast_sorcery_object_unregister() API call.

Find and unlink the specified sorcery object type to complement
ast_sorcery_object_register().  Without this function you cannot
completely unload individual modules that use sorcery for configuration.

ASTERISK-24907
Reported by: Kevin Harwell

Change-Id: I1c04634fe9a90921bf676725c7d6bb2aeaab1c88

include/asterisk/sorcery.h

@@ -616,6 +616,17 @@ int ast_sorcery_get_wizard_mapping_count(struct ast_sorcery *sorcery,
 int ast_sorcery_get_wizard_mapping(struct ast_sorcery *sorcery,
 	const char *type, int index, struct ast_sorcery_wizard **wizard, void **data);
 
+/*!
+ * \brief Unregister an object type
+ *
+ * \param sorcery Pointer to a sorcery structure
+ * \param type Type of object
+ *
+ * \retval 0 success
+ * \retval -1 failure
+ */
+int ast_sorcery_object_unregister(struct ast_sorcery *sorcery, const char *type);
+
 /*!
  * \brief Register an object type
  *

main/sorcery.c

@@ -1106,6 +1106,25 @@ static int sorcery_extended_fields_handler(const void *obj, struct ast_variable
 	return 0;
 }
 
+int ast_sorcery_object_unregister(struct ast_sorcery *sorcery, const char *type)
+{
+	struct ast_sorcery_object_type *object_type;
+	int res = -1;
+
+	ao2_wrlock(sorcery->types);
+	object_type = ao2_find(sorcery->types, type, OBJ_SEARCH_KEY | OBJ_NOLOCK);
+	if (object_type && object_type->type.type == ACO_ITEM) {
+		ao2_unlink_flags(sorcery->types, object_type, OBJ_NOLOCK);
+		res = 0;
+	}
+	ao2_unlock(sorcery->types);
+
+	/* XXX may need to add an instance unregister observer callback on success. */
+
+	ao2_cleanup(object_type);
+	return res;
+}
+
 int __ast_sorcery_object_register(struct ast_sorcery *sorcery, const char *type, unsigned int hidden, unsigned int reloadable, aco_type_item_alloc alloc, sorcery_transform_handler transform, sorcery_apply_handler apply)
 {
 	RAII_VAR(struct ast_sorcery_object_type *, object_type, ao2_find(sorcery->types, type, OBJ_KEY), ao2_cleanup);