On Thursday, 21 of February 2008, Linus Torvalds wrote:
>
> 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.
> 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).
> > 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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