Re: [Qemu-devel] Preliminary patch to implement ehci

[Max Krasnyansky]

Max Krasnyansky wrote:
> Anthony Liguori wrote:
>> Mark Burkley wrote:
>>> Hi Anthony,
>>>
>>> I have ehci built against trunk now but I am seeing an issue with a
>>> memory key I am using for testing.  ioctl returns EPIPE (which I
>>> would have thought was a STALL) to an asynchronous IN completion in
>>> usb-linux.c but then this is returned as USB_RET_NAK to EHCI which
>>> confuses my WinXP target because the transfer is then never
>>> completed.
>>>
>>> Can I just check that it was intentional to return NAK for EPIPE
>>> returns in asynchronous completions?  If so, then I will try to
>>> detect the stall in my implementation and treat differently to a
>>> NAK.  It's just that if I modify usb-linux.c to return
>>> USB_RET_STALL on -EPIPE then it works fine.
> 
> I just looked at the usb-linuc.c:async_complete() code and it looks like
> it was intentional but I cannot remember why I wrote that way. And what
> you're saying makes sense. ie It should be a STALL. In fact I think that
> might fix the regression with USB storage devices that some people have
> reported.
> I'll play some more with this later today. I want to make sure that the
> change we're talking about does not break existing devices that I
> thoroughly tested as part of the usb async re-write. If everything works
> as expected then we'll change it.

Ok. I just tested that change (ie returning STALL instead of NAK on EPIPE)
with a bunch of devices: USB serial adapter, CF card reader, USB webcam (MS
VX-3000) and MS USB mouse. All that stuff was hooked up to XP-SP3 and all of
them are perfectly usable at the same time.

In other words here is my ACK :)
I'll take a look and play with the EHCI patch later today.

Thanx
Max