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

  • From: Clemens Ladisch <clemens@xxxxxxxxxx>
  • To: wdmaudiodev@xxxxxxxxxxxxx
  • Date: Thu, 08 Oct 2009 09:41:40 +0200

Martin Gagnon wrote:
> By using a Linux OS and reproducing the same problem, we were able to
> get a lead further towards the IN control endpoint from our USB audio
> device. Again, for some reason, the bus driver is resetting the device,
> and it seems that there is a timeout on the in transactions that is
> happening (the IN transactions are at every millisecond, which we
> believe is way too often for a control endpoint sending HID input value
> from the volume up/down buttons on the chip).
> So we went ahead and disabled the HID control device from our USB audio
> device, and the problem goes away. We still want to understand why this
> situation happens.

In Linux, you can enable "USB verbose debug messages" (CONFIG_USB_DEBUG)
in the kernel configuration.  This might tell you why the reset happens,
and who initiates it.

> Does anybody know if an IN transaction for reporting button control
> value makes any sense to happen every millisecond?

I'd guess the drivers just use the interval from the descriptor.

Best regards,

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