Re: Bug in EHCI split-interrupt handling

On Tue, 24 Jul 2007, Pete Zaitcev wrote:

> On Tue, 24 Jul 2007 15:44:23 -0400 (EDT), Alan Stern <[email protected]> wrote:
> 
> > 	http://bugzilla.kernel.org/show_bug.cgi?id=8535
> > 
> > contains logs suggestive of problems with EHCI split-interrupt
> > handling.  See in particular comment #33; the usbmon log in comment #32
> > contains a line in which a low-speed interrupt URB returns with status
> > equal to 0 and actual_length set to -4.
> 
> Nicolas sent me a trace out of band which had a similar entry:
> ffff8100057f6100 1467276128 C Ii:2:004:1 0:8 -4
> 
> > Obviously this should never happen.  Can anybody offer tips on where to 
> > go searching through the driver code for a solution?
> 
> I'm going to double-check that usbmon is not deceiving you. It sure
> looks totally bogus. Maybe I mixed up fields in a union somewhere.

Maybe.  Stuart Hayes has just added comment #42 in which he suggests
this problem may be caused by the cpufreq adjustment patch he wrote.  
Stuart, could your patch cause a 4-byte low-speed interrupt transfer to
return an actual_length of -4?

Alan Stern


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