message: i915-perf: comment what is going on with i915_request_add
diff: @@ -2125,6 +2125,8 @@ void TraceEvents::init_i915_perf_event( trace_event_t &event )
  event.id_start = m_i915.perf_locs.back();
  else
  {
  + // Figure out which kernel trace point triggered this GPU generated
  + // event.
  for ( uint32_t i = 1; i <= event.id; i++ )
  {
  const trace_event_t &req_event = m_events[ event.id - i ];
  