On Thursday, 21 of February 2008, Linus Torvalds wrote:
quoted text
> 
> On Thu, 21 Feb 2008, Rafael J. Wysocki wrote:
> > 
> > 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.

Yes, sorry.

quoted text
> 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.

Well, if platform_pci_choose_state() is defined, pci_choose_state() returns
its result and on ACPI systems that points to acpi_pci_choose_state(), so in
fact it does what I said (apart from the error path). 

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.

I'm already convinced, really. :-)

Thanks,
Rafael
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