linux-kernel - Re: debugging oops after disconnecting Nexio USB touchscreen

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Date:	Fri, 4 Dec 2009 10:47:37 -0500 (EST)
From:	Alan Stern <stern@...land.harvard.edu>
To:	Ondrej Zary <linux@...nbow-software.org>
cc:	linux-usb@...r.kernel.org, <linux-kernel@...r.kernel.org>
Subject: Re: debugging oops after disconnecting Nexio USB touchscreen

On Fri, 4 Dec 2009, Ondrej Zary wrote:

> > Furthermore, the patch shows that the second-to-last argument to
> > usb_fill_bulk_urb() -- the completion function -- is NULL.  That is
> > strictly illegal and it should have caused an oops as soon as the URB
> > was used.
> 
> Thanks for catching this. usbmon showed no ACK packets so it didn't work
> at all. The device did not care. It started to work after adding a
> complete function.

What started to work?  If you don't send any ACK packets, it doesn't 
make any difference whether the completion function is set or not.


> Seems that -EPIPE is returned only after the device is disconnected. Adding a 
> check for -EPIPE to usbtouch_irq() and not submitting the urb again seems to 
> fix the problem!

Fix which problem?  The unending resubmissions or the oops in ehci-hcd?

BTW, does the touchscreen run at high speed or at full speed?

Alan Stern

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