On Mon, 8 Aug 2005, Patrick Mochel wrote:

> 
> On Sat, 6 Aug 2005, Alan Stern wrote:
> 
> > Greg and Pat:
> >
> > I've heard there's work going on to allow for manual binding and unbinding
> > of drivers to devices, although I haven't seen any of the email.  (URLs
> > appreciated!)  Here's a subtle point which may not have occurred to anyone
> > yet:  When a device has children, what should happen to them when its
> > driver is unbound?  Without a driver to manage the device, there would be
> > no way to know when the children should be removed.
> 
> Greg did the manual binding/unbinding patches. I don't know where it was
> discussed, but he wrote and article for LWN about this:
> 
> http://lwn.net/Articles/143397/

Thanks for the pointer.

> > There probably are situations where this doesn't matter.  But in general,
> > don't you think the driver core should automatically remove all children
> > below a device that has just lost its driver?  Or is it good enough to
> > rely on all the individual drivers to make sure the problem can never
> > arise?
> 
> The driver core shouldn't do anything special in this situation for
> devices that have children. It doesn't now - think of PCI bridges (either
> Host Bridges, or PCI-PCI Bridges). They have children but no drivers.
> 
> It is up to the ->remove() method in the driver to handle children. Note
> that it can now safely remove them without deadlocking (because of the
> klist patches), which was one impetus for proceeding with the development,
> AFAIK.

Okay.  I'd still like to hear from Greg about the special cases involved 
with USB hubs and root hubs.

Alan Stern



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