Re: JMS56x not working reliably with uas driver

[Oliver Neukum <oneukum-IBi9RG/b67k@public.gmane.org>]

On Tue, 2016-12-27 at 10:20 -0500, Alan Stern wrote:
> On Tue, 27 Dec 2016, Oliver Neukum wrote:
> 
> > On Thu, 2016-12-22 at 17:44 -0500, Alan Stern wrote:
> > > I don't see how this patch fixes anything.  Unless I'm mistaken, it
> > > just avoids the problem by preventing the system from issuing the
> > > command that provokes the error, rather than really fixing the
> > > underlying error.
> > 
> > Please clarify. If a reset leads to a disconnect, isn't that
> > exactly what we want?
> 
> I didn't express myself clearly enough.  Yes, if a reset leads to a 
> disconnect then avoiding the reset will avoid problems.

Good. Then we need to clarify whether the device was physically
disconnected when the logs were taken.

> But the _real_ error here is that xhci-hcd says "ERROR Transfer event
> for disabled endpoint or incorrect stream ring" when the disconnect 
> occurs during reset.  That shouldn't happen, no matter what quirks the 
> device has.  It indicates a bug either in uas or in xhci-hcd.

True. I am afraid that there necessarily is a window for resetting a
disconnected device. But the check you proposed is better.
however, I'd like to encapsulate that together with a test for
logical disconnect. Uas is unlikely to be the only driver that has
this issue.

	Regards
		Oliver




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