Re: driver power operations (was Re: suspend2 merge)

From: Pavel Machek
Date: Fri Apr 27 2007 - 08:40:56 EST


> > And, incidentally, it could possibly make both suspend and hibernate
> > work much faster too. The comments there talk about "minimally power
> > management aware" drivers which always do the wrong thing for suspend,
> > in that they always reset everything... Of course, some drivers will
> > actually need to do that, but if freeze/suspend and thaw/restart/resume
> > have the same prototypes (probably just int <function>(void)) then
> > drivers can trivially assign the same there.
> > And hibernate would benefit since a lot of drivers could do a lot less
> > work for freeze/thaw.
> I violently agree with all of the above.
> Moreover, for the hibernation we have two special cases that are of no interest
> for the suspend:
> 1) drivers compiled as modules and not loaded before we restore the image
> 2) drivers that need to allocate much memory in .freeze()
> > Or, if we don't want to have five calls and use 40 bytes (on 64-bit)
> > just for these callback pointers for each device we could just as well
> > have a single callback ->pm(what) and make "what" indicate which one of
> > these five things... But then drivers can't make that code depend on the
> > swsusp configuration which would be doable with five callbacks.
> Five callbacks are fine by me, especially if we can define reasonable defaults
> for the hibernation (and can we?).

Well, we still can default to suspend(PMSG_FREEZE) for freeze(), and
resume() for thaw(). Anything else is just not sane way forward.
(cesky, pictures)
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