Re: Re: [PATCH] swsusp: do not use pm_ops (was: Re: suspend2 merge (was: Re: CFS and suspend2: hang in atomic copy))

[Pavel Machek <pavel@ucw.cz>]

Hi!

> > ACPI BIOS communicates with hw, too. Suppose it generates random
> > number, stores it in memory and tells it to the keyboard conroller
> > during bootup (more specifically during ACPI enable phase).
> > 
> > Now, it periodically checks if number in memory is same as the number
> > known by keyboard controller.
> > 
> > If you suspend/resume without telling acpi, it will find out, because
> > numbers will not match.
> > 
> > (And now, ACPI is probably not crazy enough to store random numbers --
> > but it could -- but for example "I had AC power, now I do not, and I
> > did not see a interrupt telling me it went away" can be counted as
> > confusing for ACPI).
> 
> I don't follow.
> 
>  * you have AC power.
>  * you save system state and shut down (S5)
>  * you boot up again on battery power
>  * you restore system state
>  * ...
> 
> vs.
> 
>  * you have AC power
>  * you shut down
>  * you boot up again on battery power
>  * ...
> 
> where's the difference to the ACPI bios? Oh, I see, it stores it
> somewhere in the memory that you've stored/restored? Well, that's your
> bug then, don't touch it.

Not sure... yes, it stores parts somewhere in memory. Plus, it may
have some parts related to the communications with operating system
(*)... I guess we need to save those, and parts related to hw
state... where your suggestion makes sense.

(*) and yes, there probably are such parts. If we set backlight to
20%, we'll be confused if it is 100% after resume... we probably could
handle those one-by-one...
								Pavel
-- 
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