[CMD][CONFIG] Add additional check to touch selection and add comments

cmd/seco_config_lib.c

@@ -1206,18 +1206,32 @@ int selection_touch_mode (touch_mode_t touch_mode_list[], int num_element) {
 }
 
 int set_touch_mode( int fdt_selected_device ) {
-	int touch_mode_selection;
+	int touch_mode_selection = -1;
+
 #ifdef CONFIG_OF_LIBFDT_OVERLAY
 	char touch_overlay_list[256];
 	char *fdt_overlay_touch_load;
-#endif
 
-	/* select touch mode configuration */
+	/*
+	 * The touch_mode_list might be empty (for devices without
+	 * a configurable touch controller). Double check if the
+	 * list is initialized and exit if not. Also see the general
+	 * checks for ENV_NUM_TOUCH.
+	 */
+	if ( ! gd->boot_setup.touch_mode_list )
+		return 0;
+
+	/*
+	 * Show the sub-selection for the touch
+	 * controller and set the user selection.
+	 */
 	touch_mode_selection = selection_touch_mode( gd->boot_setup.touch_mode_list,
 				gd->boot_setup.touch_mode_num );
 
-#ifdef CONFIG_OF_LIBFDT_OVERLAY
-		/* touch setting for a fdt overlay file */
+	/*
+	 * Set the environment command for loading
+	 * the devicetree overlay for the touch controller.
+	 */
 	memset( touch_overlay_list, 0, sizeof( touch_overlay_list ) );
 
 	if ( gd->boot_setup.touch_mode_list[touch_mode_selection].dtbo_conf_file != NULL ) {
@@ -1234,7 +1248,11 @@ int set_touch_mode( int fdt_selected_device ) {
 #endif
 		}
 	} else {
-			/* Clear overlay list and command if nothing is selected */
+		/*
+		 * Clear the devicetree overlay list and
+		 * command from the environment if nothing
+		 * is selected.
+		 */
 		SAVE_FDT_OVERLAY_TOUCH_LIST( "" );
 		SAVE_FDT_OVERLAY_TOUCH_CMD( "" );
 	}