add abstraction for listing config files as well

file.c

@@ -442,7 +442,7 @@ static inline char *get_filename(char *path)
 	return p;
 }
 
-int uci_list_configs(struct uci_context *ctx, char ***list)
+static char **uci_list_config_files(struct uci_context *ctx)
 {
 	char **configs;
 	glob_t globbuf;
@@ -450,8 +450,6 @@ int uci_list_configs(struct uci_context *ctx, char ***list)
 	char *buf;
 	char *dir;
 
-	UCI_HANDLE_ERR(ctx);
-
 	dir = uci_malloc(ctx, strlen(ctx->confdir) + 1 + sizeof("/*"));
 	sprintf(dir, "%s/*", ctx->confdir);
 	if (glob(dir, GLOB_MARK, NULL, &globbuf) != 0)
@@ -481,10 +479,8 @@ int uci_list_configs(struct uci_context *ctx, char ***list)
 		strcpy(buf, p);
 		buf += strlen(buf) + 1;
 	}
-	*list = configs;
 	free(dir);
-
-	return 0;
+	return configs;
 }
 
 static struct uci_package *uci_file_load(struct uci_context *ctx, const char *name)
@@ -536,4 +532,5 @@ static struct uci_backend uci_file_backend = {
 	.name = "file",
 	.load = uci_file_load,
 	.commit = uci_file_commit,
+	.list_configs = uci_list_config_files,
 };

libuci.c

@@ -158,6 +158,15 @@ void uci_perror(struct uci_context *ctx, const char *prefix)
 	}
 }
 
+int uci_list_configs(struct uci_context *ctx, char ***list)
+{
+	UCI_HANDLE_ERR(ctx);
+	UCI_ASSERT(ctx, list != NULL);
+	UCI_ASSERT(ctx, ctx->backend && ctx->backend->list_configs);
+	*list = ctx->backend->list_configs(ctx);
+	return 0;
+}
+
 int uci_commit(struct uci_context *ctx, struct uci_package **package, bool overwrite)
 {
 	UCI_HANDLE_ERR(ctx);

uci.h

@@ -299,6 +299,7 @@ struct uci_element
 struct uci_backend
 {
 	const char *name;
+	char **(*list_configs)(struct uci_context *ctx);
 	struct uci_package *(*load)(struct uci_context *ctx, const char *name);
 	void (*commit)(struct uci_context *ctx, struct uci_package **p, bool overwrite);
 };