Re: Null Pointer BUG in uhci_hcd

Michael S. Zick
2009-07-08T22:31:50Z

On Wed July 8 2009, Alan Stern wrote:
> On Wed, 8 Jul 2009, Michael S. Zick wrote:
>
> > > Like I've been telling you all along, the hardware isn't working.
> > >
> >
> > That sounds very fragile.
>
> I'm not sure how to interpret that sentence. If you mean that your
> system's hardware design isn't good, I agree. If you mean that the
> kernel shouldn't produce a lot of output when faced with broken
> hardware, that's not so clear. What else should it do (bearing in mind
> that the kernel can't tell the hardware is broken)?
>

It is unlikely that VIA Tech. will recall the CX700 chipset.

So being able to take a device off-line (like the driver claims it is doing)
and *leave* it off-line - until told to "try again" - that would be an
improvement.

The current process of filling up the /var/log directory until the machine
chokes is a rather fragile sort of response to a hot-plugged device, good or bad.

> > > I suspect it's worse than a simple interrupt-routing mistake.
> > >
> >
> > I would not object to your removing that one mistake - that is one less
> > to contend with.
>
> I didn't say there was an interrupt-routing mistake; I said it was
> _worse_ than an interrupt-routing mistake.
>

Never claimed you did - the driver made that claim.
But still, it would be nice to get rid of the interrupt-routing mistake.

I suppose waiting for the OLPC project to find and fix the problem is
a viable alternative also.
You will not be the first to give up on this C7-M/CX700 combination. ;)

> > > > > > For more information enable CONFIG_USB_DEBUG and CONFIG_DEBUG_FS, then
> > > > > > see what's sitting in the usb/uhci/* files in debugfs.
> > > > > >
> > > >
> >
> > Fours up-time - nothing written to dmesg since boot -
> > Just the usual hard-lockup.
> >
> > Also - something in the combined fix/diagnostic patch
> > disable any sensing of external usb events.
> > So I couldn't very well poke devices at it. ;)
>
> You should take out those BUG statements. If they ever trigger, they
> will certainly lock up your system.
>

Although I would expect that they not do so silently.

I take them out and just in time before starting the next
round of testing.

Mike
> Alan Stern
>
>
>