diff
+#include <assert.h>
+
 void drm_client_register(struct drm_client_dev *client)
 {
+    assert(client != NULL);
+    assert(client->dev != NULL);
     struct drm_device *dev = client->dev;
     int ret;
 
     mutex_lock(&dev->clientlist_mutex);
     // ... rest of the function
 }
