On Thu, 21 Feb 2008, Rafael J. Wysocki wrote:
quoted text
> 
> In fact we have acpi_pci_choose_state() that tells the driver which power
> state to put the device into in ->suspend().  If that is used, the device ends
> up in the state expected by to BIOS for S4.

First off, nobody should *ever* use that directly anyway.

Secondly, the one that people should use ("pci_choose_state()") doesn't 
actually do what you claim it does. It does all kinds of wrong things, and 
doesn't even take the target state into account at all. So look again.

quoted text
> No.  Again, if there are devices that wake us up from S4, but not from S5,
> they need to be handled differently in the *enter S4* case (hibernation) and
> in the *enter S5* case (powering off the system).

And again, what does this have to do with (the example I used) the 
graphics hardware? Answer: nothing. The example I gave you we simply DO 
THE WRONG THING FOR.

Same thing for things like USB devices - where pci_choose_state() doesn't 
work to begin with. Why do we call "suspend()" on such a thing when we 
don't want to suspend it? We shouldn't. We should call "freeze/unfreeze" 
(which are no-ops) and then finally perhaps "poweroff", and that final 
stage might want to spin things down or similar.

But *none* of it has anything to do with suspend, and none of it has 
anything to do with pci_choose_state() (much less acpi_pci_choose_state)

The fact is, we should let the driver decide, and we should make it clear 
to the driver writer what he is deciding about - rather than basically lie 
and say "suspend the device and put it into D3" even when that's the last 
thing it should ever do.

			Linus
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