drm/sysfs: Register "ddc" symlink later

Currently drm_sysfs_connector_add() attempts to register
the "ddc" symlink (based one connector->ddc) before the
driver's .early_register() hook has been called. That is
too early for i915 which only fully registers the aux ch
and associated i2c bus from said hook (to prevent half
initialized stuff getting exposed to userspace). This
causes my attempt at using drm_connector_init_with_ddc()
to fail, and the entire connector disappears from sysfs
on account of sysfs_create_link() failing.

To fix that split the sysfs symlink stuff into separate
functions (drm_sysfs_connector_add_late() and
drm_sysfs_connector_remove_early()) which are called
on the opposite side of the .later_register() and
.early_unregister() hooks.

Cc: Andrzej Pietrasiewicz <andrzej.p@collabora.com>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Andrzej Hajda <a.hajda@samsung.com>
Cc: Emil Velikov <emil.velikov@collabora.com>
Cc: Sam Ravnborg <sam@ravnborg.org>
Cc: Neil Armstrong <narmstrong@baylibre.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230829113920.13713-3-ville.syrjala@linux.intel.comReviewed-by: Jani Nikula <jani.nikula@intel.com>
Acked-by: Thomas Zimmermann <tzimmermann@suse.de> #irc

drivers/gpu/drm/drm_connector.c

@@ -631,6 +631,10 @@ int drm_connector_register(struct drm_connector *connector)
 			goto err_debugfs;
 	}
 
+	ret = drm_sysfs_connector_add_late(connector);
+	if (ret)
+		goto err_late_register;
+
 	drm_mode_object_register(connector->dev, &connector->base);
 
 	connector->registration_state = DRM_CONNECTOR_REGISTERED;
@@ -647,6 +651,9 @@ int drm_connector_register(struct drm_connector *connector)
 	mutex_unlock(&connector_list_lock);
 	goto unlock;
 
+err_late_register:
+	if (connector->funcs->early_unregister)
+		connector->funcs->early_unregister(connector);
 err_debugfs:
 	drm_debugfs_connector_remove(connector);
 	drm_sysfs_connector_remove(connector);
@@ -681,6 +688,8 @@ void drm_connector_unregister(struct drm_connector *connector)
 					connector->privacy_screen,
 					&connector->privacy_screen_notifier);
 
+	drm_sysfs_connector_remove_early(connector);
+
 	if (connector->funcs->early_unregister)
 		connector->funcs->early_unregister(connector);
 

drivers/gpu/drm/drm_internal.h

@@ -153,6 +153,8 @@ int drm_sysfs_init(void);
 void drm_sysfs_destroy(void);
 struct device *drm_sysfs_minor_alloc(struct drm_minor *minor);
 int drm_sysfs_connector_add(struct drm_connector *connector);
+int drm_sysfs_connector_add_late(struct drm_connector *connector);
+void drm_sysfs_connector_remove_early(struct drm_connector *connector);
 void drm_sysfs_connector_remove(struct drm_connector *connector);
 
 void drm_sysfs_lease_event(struct drm_device *dev);

drivers/gpu/drm/drm_sysfs.c

@@ -400,10 +400,6 @@ int drm_sysfs_connector_add(struct drm_connector *connector)
 			drm_err(dev, "failed to add component to create link to typec connector\n");
 	}
 
-	if (connector->ddc)
-		return sysfs_create_link(&connector->kdev->kobj,
-				 &connector->ddc->dev.kobj, "ddc");
-
 	return 0;
 
 err_free:
@@ -411,13 +407,25 @@ int drm_sysfs_connector_add(struct drm_connector *connector)
 	return r;
 }
 
-void drm_sysfs_connector_remove(struct drm_connector *connector)
+int drm_sysfs_connector_add_late(struct drm_connector *connector)
 {
-	if (!connector->kdev)
-		return;
+	if (connector->ddc)
+		return sysfs_create_link(&connector->kdev->kobj,
+					 &connector->ddc->dev.kobj, "ddc");
+
+	return 0;
+}
 
+void drm_sysfs_connector_remove_early(struct drm_connector *connector)
+{
 	if (connector->ddc)
 		sysfs_remove_link(&connector->kdev->kobj, "ddc");
+}
+
+void drm_sysfs_connector_remove(struct drm_connector *connector)
+{
+	if (!connector->kdev)
+		return;
 
 	if (dev_fwnode(connector->kdev))
 		component_del(connector->kdev, &typec_connector_ops);