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SubjectRe: [RFC] Fix Device Power Management States

On Mon, 9 Aug 2004, Pavel Machek wrote:

> Well, "no DMA" needs to be part of definition, too, because some
> devices (USB) do DMA only if they have nothing to do.

I don't understand; that doesn't sound healthy.

> if something like this gets merged, it will immediately break swsusp
> because initially no drivers will have "stop" methods.
>
> Passing system state down to drivers and having special "quiesce"
> (as discussed in rather long thread) state has advantage of
> automagicaly working on drivers that ignore u32 parameter of suspend
> callback (and that's most of them). David's patches do not bring us
> runtime suspend capabilities, but do not force us to go through all
> the drivers, either...

Nothing is free. ;)

We've been talking about creating and merging a sane power management
model for 3+ years now. It's always been known that the drivers will have
to be modified to support a sane model. It's a fact of life. At some
point, we have to bite the bullet and do the work. I see that time rapidly
approaching.

I do not intend to merge a patch that will break swsusp in a stable
kernel. However, we do have this wonderful thing called the -mm tree in
which we can a) evolve the model, b) get large testing coverage and c)
solicit driver fixes.

Once the swsusp consolidation is merged upstream, I will merge a new
device power model in -mm, and we can start working on the drivers. How
does that sound?


Pat
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