+/* backend operates itself types */
+static tdm_private_output*
+_look_for_frontend_hwc_output(tdm_output *backend_output)
+{
+ tdm_private_output *frontend_output = NULL, *o = NULL;
+ tdm_private_display *private_display = tdm_display_get();
+ tdm_private_module *private_module = NULL;
+
+ LIST_FOR_EACH_ENTRY(private_module, &private_display->module_list, link) {
+ LIST_FOR_EACH_ENTRY(o, &private_module->output_list, link) {
+ if (!(o->caps.capabilities & TDM_OUTPUT_CAPABILITY_HWC))
+ continue;
+
+ if (o->output_backend == backend_output) {
+ frontend_output = o;
+ return frontend_output;
+ }
+ }
+ }
+
+ return NULL;
+}
+
+EXTERN tdm_error
+tdm_backend_trigger_need_validate_event(tdm_output *output)
+{
+ tdm_private_output *private_output;
+ uint64_t value;
+ int res;
+
+ private_output = _look_for_frontend_hwc_output(output);
+ TDM_RETURN_VAL_IF_FAIL(private_output != NULL, TDM_ERROR_INVALID_PARAMETER);
+
+ value = 1;
+
+ /* do not lock the global display lock here */
+
+ res = write(private_output->need_validate.event_fd, &value, sizeof(value));
+ if (res < 0)
+ return TDM_ERROR_OPERATION_FAILED;
+
+ return TDM_ERROR_NONE;
+}