backend/drm: de-duplicate wlr_drm_mode creation

Introduce a function to convert a drmModeModeInfo into a new
wlr_drm_mode.

backend/drm/drm.c

@@ -750,6 +750,23 @@ static bool drm_connector_set_mode(struct wlr_drm_connector *conn,
 	return true;
 }
 
+static struct wlr_drm_mode *drm_mode_create(const drmModeModeInfo *modeinfo) {
+	struct wlr_drm_mode *mode = calloc(1, sizeof(*mode));
+	if (!mode) {
+		return NULL;
+	}
+
+	mode->drm_mode = *modeinfo;
+	mode->wlr_mode.width = mode->drm_mode.hdisplay;
+	mode->wlr_mode.height = mode->drm_mode.vdisplay;
+	mode->wlr_mode.refresh = calculate_refresh_rate(modeinfo);
+	if (modeinfo->type & DRM_MODE_TYPE_PREFERRED) {
+		mode->wlr_mode.preferred = true;
+	}
+
+	return mode;
+}
+
 struct wlr_output_mode *wlr_drm_connector_add_mode(struct wlr_output *output,
 		const drmModeModeInfo *modeinfo) {
 	struct wlr_drm_connector *conn = get_drm_connector_from_output(output);
@@ -766,21 +783,17 @@ struct wlr_output_mode *wlr_drm_connector_add_mode(struct wlr_output *output,
 		}
 	}
 
-	struct wlr_drm_mode *mode = calloc(1, sizeof(*mode));
+	struct wlr_drm_mode *mode = drm_mode_create(modeinfo);
 	if (!mode) {
 		return NULL;
 	}
-	memcpy(&mode->drm_mode, modeinfo, sizeof(*modeinfo));
 
-	mode->wlr_mode.width = mode->drm_mode.hdisplay;
-	mode->wlr_mode.height = mode->drm_mode.vdisplay;
-	mode->wlr_mode.refresh = calculate_refresh_rate(modeinfo);
+	wl_list_insert(&conn->output.modes, &mode->wlr_mode.link);
 
 	wlr_drm_conn_log(conn, WLR_INFO, "Registered custom mode "
 			"%"PRId32"x%"PRId32"@%"PRId32,
 			mode->wlr_mode.width, mode->wlr_mode.height,
 			mode->wlr_mode.refresh);
-	wl_list_insert(&conn->output.modes, &mode->wlr_mode.link);
 
 	return &mode->wlr_mode;
 }
@@ -1362,23 +1375,14 @@ void scan_drm_connectors(struct wlr_drm_backend *drm,
 			wlr_log(WLR_INFO, "Detected modes:");
 
 			for (int i = 0; i < drm_conn->count_modes; ++i) {
-				struct wlr_drm_mode *mode = calloc(1, sizeof(*mode));
-				if (!mode) {
-					wlr_log_errno(WLR_ERROR, "Allocation failed");
-					continue;
-				}
-
 				if (drm_conn->modes[i].flags & DRM_MODE_FLAG_INTERLACE) {
-					free(mode);
 					continue;
 				}
 
-				mode->drm_mode = drm_conn->modes[i];
-				mode->wlr_mode.width = mode->drm_mode.hdisplay;
-				mode->wlr_mode.height = mode->drm_mode.vdisplay;
-				mode->wlr_mode.refresh = calculate_refresh_rate(&mode->drm_mode);
-				if (mode->drm_mode.type & DRM_MODE_TYPE_PREFERRED) {
-					mode->wlr_mode.preferred = true;
+				struct wlr_drm_mode *mode = drm_mode_create(&drm_conn->modes[i]);
+				if (!mode) {
+					wlr_log_errno(WLR_ERROR, "Allocation failed");
+					continue;
 				}
 
 				// If this is the current mode set on the conn's crtc,