David, Charles, and everybody:

This is just a quick summary of my recent results.  I tried running the 
usbtest endpoint-0 tests on two different computers, running the same 
kernel and talking to the same USB device.  The difference was that the 
desktop system has an OHCI controller and the laptop has a UHCI 
controller.

With OHCI, test 10 ran perfectly.  With UHCI it didn't, although my 
symptoms were quite different from what happened to Charles.  Every single 
time, the first control transfer succeeded and the second one stalled.  
That happened even when I swapped the case labels in the usbtest source, 
so that the subtest 1 packet was sent first and the subtest 0 packet 
second.  Clearly there's something wrong with the control transfer 
queueing in the UHCI driver.  (It's vaguely possible that it might be 
related to the changes Duncan Sands has been working on -- I haven't had 
time to look at them yet.)

I still don't have more than a clue what the real problem is.  But I did
track down about a half-dozen other problems or things-to-change!  I'll
post more details tomorrow.  Briefly: I've got some patches for usbtest,
nuke_urbs() is used wrongly in usb.c, hcd_endpoint_disable() has an
irq-related error, and hub_events() could stand to be written a little
more defensively.

Alan Stern



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