drm/client: Add hotplug_failed flag

Signal failed hotplugging with a flag in struct drm_client_dev. If set,
the client helpers will not further try to set up the fbdev display.

This used to be signalled with a combination of cleared pointers in
struct drm_fb_helper, which prevents us from initializing these pointers
early after allocation.

The change also harmonizes behavior among DRM clients. Additional DRM
clients will now handle failed hotplugging like fbdev does.
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230125200415.14123-3-tzimmermann@suse.de

drivers/gpu/drm/drm_client.c

@@ -208,8 +208,13 @@ void drm_client_dev_hotplug(struct drm_device *dev)
 		if (!client->funcs || !client->funcs->hotplug)
 			continue;
 
+		if (client->hotplug_failed)
+			continue;
+
 		ret = client->funcs->hotplug(client);
 		drm_dbg_kms(dev, "%s: ret=%d\n", client->name, ret);
+		if (ret)
+			client->hotplug_failed = true;
 	}
 	mutex_unlock(&dev->clientlist_mutex);
 }

drivers/gpu/drm/drm_fbdev_generic.c

@@ -382,10 +382,6 @@ static int drm_fbdev_client_hotplug(struct drm_client_dev *client)
 	struct drm_device *dev = client->dev;
 	int ret;
 
-	/* Setup is not retried if it has failed */
-	if (!fb_helper->dev && fb_helper->funcs)
-		return 0;
-
 	if (dev->fb_helper)
 		return drm_fb_helper_hotplug_event(dev->fb_helper);
 

include/drm/drm_client.h

@@ -106,6 +106,14 @@ struct drm_client_dev {
 	 * @modesets: CRTC configurations
 	 */
 	struct drm_mode_set *modesets;
+
+	/**
+	 * @hotplug failed:
+	 *
+	 * Set by client hotplug helpers if the hotplugging failed
+	 * before. It is usually not tried again.
+	 */
+	bool hotplug_failed;
 };
 
 int drm_client_init(struct drm_device *dev, struct drm_client_dev *client,