Re: [Libusb-devel] issue with testing USB3.0 with new kernel

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Hi Sarah,

Sarah Sharp wrote:
> Here is the other mail I was referring to in the thread with shashank.
> 
> Alan, perhaps there's a change from 2.6.38 to 3.0 that makes the USB
> core request a string descriptor that the USB devices don't like?
> 
> On Tue, Mar 27, 2012 at 08:23:03PM +0530, Aditya Mittal wrote:
> > We see a request for string descriptor 238 (0xEE) which is a microsoft
> > specific descriptor with kernel 3.0.0 whereas we do not see a request for
> > this string descriptor for version 2.6.38.

Interesting. The 0xee string is indeed a Microsoft USB extension. It
can be used to tell Windows what driver it should use for the device.
Works really well out of the box on Windows 8 and later.

I'm also surprised if Linux is sending that. I'm not saying that it's
wrong, just surprised. In any case, any device *must* be able to deal
with a request for a string descriptor which doesn't exist.

This is clearly a problem in the device, regardless of where the 0xee
request is coming from. (Wild guess: virtual machine someone forgot
was still running?) Windows XPSP1 and later ask exactly once for the
string descriptor, for every device that hasn't been seen before.


//Peter
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