QSocketNotifier activated() not firing

I am trying to key off of the activated signal, but it doesnt seem to be triggering. I am using a USB serial device, and opening it up as a QFile, then passing the file descriptor into the QSocketNotifier on construction. The activated signal will fire on one computer with the same device hooked up, but won't on another computer. Is there some kernel configuration I'm missing? I looked at inotify and dnotify support, and both are enabled.

I finally got this working, after many hours of fighting with the port settings. Nothing to do with Qt at all :D