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Re: Drivers without suspend/resume/reset-resume support

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Am Donnerstag 11 Oktober 2007 schrieb Alan Stern:
> On Thu, 11 Oct 2007, Oliver Neukum wrote:
> 
> > > > > One way around the problem would be to unbind these bad drivers before
> > > > > the suspend begins, say in a notifier routine.  That would leave a
> > > > 
> > > > Problematic. You'd have to get the order of doing stuff exactly right.
> > > 
> > > What order are you concerned about?  It will be impossible to have
> > 
> > Blocking new device additions vs. calling disconnect.
> 
> If we disconnect the bad drivers after khubd has gone to sleep then no 
> new devices will be added.  There's still the possibility of userspace 
> causing a bind via sysfs, though.

Driver loading, change of configuration, ...
Did you check the other code paths?

> > > Of course there's always the other approach -- solve the problem by 
> > > adding suspend and resume methods to every driver!
> > 
> > Are you volunteering?
> 
> How many drivers are we talking about?

Dozens, which will require testing.

> > Resumption may involve IO, which therefore may fail. I cannot see the reason
> > to not count the lack of a resume method as a failure. We'll have to deal with
> > them anyway, especially for reset_resume.
> 
> If a driver doesn't have a suspend or resume method, then resuming it 
> can't involve I/O.  :-)

You still can have IO to a hub to wake the device.

> You appear to be saying that if a driver doesn't have a resume method,
> or the resume method returns an error, then the driver should be
> unbound as soon as possible.  For non-system non-auto resumes this is

Yes.

> right away, but for system resumes it isn't until the driver core is
> stable again.  Likewise, non-system suspends should fail if a driver

Yes.

> doesn't have a suspend method (I'm not so sure about this part).

Yes.

	Regards
		Oliver


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