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

2 files changed, 11 insertions, 0 deletions

diff --git a/drivers/gpu/drm/drm_crtc.c b/drivers/gpu/drm/drm_crtc.c
index 23dfec41decb..ea5ec641eacc 100644
--- a/drivers/gpu/drm/drm_crtc.c
+++ b/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);
 
diff --git a/include/drm/drm_crtc.h b/include/drm/drm_crtc.h
index 4cc170cfc8fd..c2734979f164 100644
--- a/include/drm/drm_crtc.h
+++ b/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;