drm: Make drm_connector_register() safe against multiple calls

Protect against drivers that may try to register the connector more
than once, or who try to unregister it multiple times.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Dave Airlie <airlied@redhat.com>
Cc: dri-devel@lists.freedesktop.org
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/1465993109-19523-4-git-send-email-chris@chris-wilson.co.uk

drivers/gpu/drm/drm_crtc.c

@@ -984,6 +984,9 @@ int drm_connector_register(struct drm_connector *connector)
 {
 	int ret;
 
+	if (connector->registered)
+		return 0;
+
 	ret = drm_sysfs_connector_add(connector);
 	if (ret)
 		return ret;
@@ -1001,6 +1004,7 @@ int drm_connector_register(struct drm_connector *connector)
 
 	drm_mode_object_register(connector->dev, &connector->base);
 
+	connector->registered = true;
 	return 0;
 
 err_debugfs:
@@ -1019,11 +1023,16 @@ EXPORT_SYMBOL(drm_connector_register);
  */
 void drm_connector_unregister(struct drm_connector *connector)
 {
+	if (!connector->registered)
+		return;
+
 	if (connector->funcs->early_unregister)
 		connector->funcs->early_unregister(connector);
 
 	drm_sysfs_connector_remove(connector);
 	drm_debugfs_connector_remove(connector);
+
+	connector->registered = false;
 }
 EXPORT_SYMBOL(drm_connector_unregister);
 

include/drm/drm_crtc.h

@@ -1193,6 +1193,7 @@ struct drm_encoder {
  * @interlace_allowed: can this connector handle interlaced modes?
  * @doublescan_allowed: can this connector handle doublescan?
  * @stereo_allowed: can this connector handle stereo modes?
+ * @registered: is this connector exposed (registered) with userspace?
  * @modes: modes available on this connector (from fill_modes() + user)
  * @status: one of the drm_connector_status enums (connected, not, or unknown)
  * @probed_modes: list of modes derived directly from the display
@@ -1249,6 +1250,7 @@ struct drm_connector {
 	bool interlace_allowed;
 	bool doublescan_allowed;
 	bool stereo_allowed;
+	bool registered;
 	struct list_head modes; /* list of modes on this connector */
 
 	enum drm_connector_status status;