> > > > Driver disconnect() routines need to unlink ALL urbs as well as
> > > > make sure that no other driver entries (file operations, say) will
> > > > ever try to use that device again (even while unlinking proceeds).
> > >
> > > Then I hope that disconnect() is not called on an irq!
> >
> > Only in uncommon error recovery situations, AFAIK. That's is a
> > good reason to use async unlink in disconnect() though.
>
> disconnect is guaranteed to only happen in a process context (khubd,
> rmmod, etc)
Not when it's called from the pci_driver remove() method, which
Documentation/pci.txt says "can be called from interrupt context".
By my observation that's not common. However, remove() must
currently be able to get rid of every driver-to-device binding... the
HCDs need that to happen before the root hub can vanish.
> > What disconnect() means is: as of this instant, you can't depend on
> > being able to do I/O with this device any more. And when that
> > disconnect() returns, the pointer becomes invalid/unusable.
>
> Not exactly true. With the reference counting, the pointer can still be
> valid. It usually not usable tho since the device is gone now.
Well, focus on the "unusable" part. Actually I should have said
"interface" not "device" ... sometimes drivers may need to get
disconnected while the device is still present (letting some other
driver connect, say).
> > So disconnect() should clear the usb_device pointer in the driver's
> > record. That'd be one way that all other execution contexts in
> > the driver (timer, sleeping process/thread, etc) would know that
> > particular device is disconnected. The driver would free its own
> > record of device state when the last context stopped using it.
>
> Or take advantage of the reference counting.
I'd null the pointer in any case ... since we know that can produce
a consistent error, but violation of refcount rules produce really
strange errors. Like one I just tripped over in usb.c ... :)
- Dave
> JE
>
>
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