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

[Max Krasnyansky <maxk@kernel.org>]

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.

btw It's awesome that you're working on EHCI. I was going to work on it 
right after making the stack fully async but got swamped with other 
things. Do you have a git tree I could pull your stuff from ?

Thanx
Max