Add error checking to DRM legacy

backend/drm/drm-legacy.c

@@ -9,11 +9,17 @@ static bool legacy_crtc_pageflip(struct wlr_drm_backend *backend,
 		struct wlr_drm_output *output, struct wlr_drm_crtc *crtc,
 		uint32_t fb_id, drmModeModeInfo *mode) {
 	if (mode) {
-		drmModeSetCrtc(backend->fd, crtc->id, fb_id, 0, 0,
-			&output->connector, 1, mode);
+		if (drmModeSetCrtc(backend->fd, crtc->id, fb_id, 0, 0,
+				&output->connector, 1, mode)) {
+			wlr_log_errno(L_ERROR, "%s: Failed to set CRTC", output->output.name);
+			return false;
+		}
 	}
 
-	drmModePageFlip(backend->fd, crtc->id, fb_id, DRM_MODE_PAGE_FLIP_EVENT, output);
+	if (drmModePageFlip(backend->fd, crtc->id, fb_id, DRM_MODE_PAGE_FLIP_EVENT, output)) {
+		wlr_log_errno(L_ERROR, "%s: Failed to page flip", output->output.name);
+		return false;
+	}
 
 	return true;
 }