On Thu, 30 Aug 2012, Sebastian Andrzej Siewior wrote:

> >So the problem appears to be that dummy-hcd doesn't implement the right
> >interval for periodic transfers.  I'd accept a patch to fix that.
> 
> That is also missing. However, we are pulled down, that means 
> find_endpoint() in dummy returns always NULL due to !active(). So we 
> never get here to delay the interrupt packet.

You're missing the point.  The test of the interrupt URB's interval
should be done _before_ find_endpoint() is called.

That's how real host controllers work; they don't try to contact
interrupt endpoints during frames that aren't in the endpoint's
schedule.

(The same goes for isochronous endpoints... but dummy-hcd currently 
doesn't support isochronous at all.)

Alan Stern

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