On Tue, 2 Jul 2013, Martin van Es wrote:

> Here's the usbmon output on my old USB2 laptop, kernel 3.9.1
> Including the plug/unplug events. scanimage -L succesfully reports the
> scanner and returns the prompt.

The two usbmon traces are essentially identical (including the -71
errors!) right up to the point where the problem occurred.  The only
difference that might be relevant is that on the USB-3 port, transfers
take place more quickly.

Maybe that's the explanation: The scanner isn't able to cope when the 
packets arrive too rapidly.  It _is_ clear from the usbmon data that 
the scanner is at least slightly buggy.

On the other hand, it's also possible that a bug in the xHCI hardware
or driver caused the scanner's response to get lost.  I'm not sure how 
you can tell what's really going on without using a USB bus analyzer.

Alan Stern

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