[wdmaudiodev] Re: Debugging USB audio at the hardware level

  • From: Clemens Ladisch <clemens@xxxxxxxxxx>
  • To: wdmaudiodev@xxxxxxxxxxxxx
  • Date: Mon, 21 Sep 2009 19:03:51 +0200

Martin Gagnon wrote:
> If only the OS can tell the USB controller to generate that Reset
> event, then this leads me to my next logical suspect, which are the IN
> transactions that suddenly stop.
> Why would they stop happening? Would it make sense to assume that it
> is also the host controller driver in the OS that stops these IN
> transactions before sending the Reset event isochronous OUT endpoint?

The reset has no destination address; it's a special state of the USB
signal lines and affects all devices on that bus.

The OS will (try to) stop all scheduled transactions before resetting.

> Meaning that a problem happened prior to the IN transactions stopped?

Yes.  Unfortunately, there is no indication why the OS/driver decided
to reset.  Does this happen with other OSes?

Best regards,

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