-bool keymap_is_special_mode(int fn_bits);
-/* process Fn keys. This.should be called every scan. */
-void keymap_fn_proc(int fn_bits);
+/* layer to move during press Fn key */
+uint8_t keymap_fn_layer(uint8_t fn_bits);
+
+/* keycode to send when release Fn key without using */
+uint8_t keymap_fn_keycode(uint8_t fn_bits);
+
+/* whether special key combination */
+bool keymap_is_special_mode(uint8_t fn_bits);