libinput backend: add wlr_input_device_is_libinput

backend/libinput/events.c

@@ -53,6 +53,10 @@ static struct wlr_input_device *allocate_device(
 	return wlr_dev;
 }
 
+bool wlr_input_device_is_libinput(struct wlr_input_device *wlr_dev) {
+        return wlr_dev->impl == &input_device_impl;
+}
+
 static void handle_device_added(struct wlr_libinput_backend *backend,
 		struct libinput_device *libinput_dev) {
 	assert(backend && libinput_dev);

include/wlr/backend/libinput.h

@@ -12,5 +12,6 @@ struct wlr_backend *wlr_libinput_backend_create(struct wl_display *display,
 struct libinput_device *wlr_libinput_get_device_handle(struct wlr_input_device *dev);
 
 bool wlr_backend_is_libinput(struct wlr_backend *backend);
+bool wlr_input_device_is_libinput(struct wlr_input_device *device);
 
 #endif