diff
 void drm_client_register(struct drm_client_dev *client)
 {
         struct drm_device *dev = client->dev;
         int ret;
+        if (!dev) {
+            pr_err("drm_client_register: NULL device\n");
+            goto out;
+        }
         mutex_lock(&dev->clientlist_mutex);
         list_add(&client->list, &dev->clientlist);
+out:
+        return;
 }
