Drivers without suspend/resume/reset-resume support

Oliver:

We discussed earlier that if a driver doesn't have suspend/resume 
support, it ought to be unbound when its device is suspended.  
Likewise, if a driver doesn't have reset-resume support then it ought 
to be unbound when a reset-resume occurs.

It turns out this isn't as easy as it sounds.  Upcoming changes to the
driver and PM cores will make it very dangerous to unbind drivers
during a system suspend: If the driver's disconnect method tries to
unregister a child device, it will deadlock.  (Likewise, although it
doesn't matter for our purposes at the moment, if the driver tries to
register a child device, the registration will fail.)

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
question about how to handle non-system suspends, such as when the user 
does "echo suspend >/sys/.../power/level".  But it's a nuisance any way 
you look at it.

The reset-resume problem is even worse, since we don't know beforehand
when a reset-resume will be needed.

Do you have any suggestions?

Alan Stern


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