Re: [patch] pm: fix runtime powermanagement's /sys interface

Adam Belay
2006-01-07T05:58:07Z

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On Fri, Jan 06, 2006 at 04:00:05PM +0100, Dominik Brodowski wrote:
> Hi,
>
> On Thu, Jan 05, 2006 at 05:37:30PM -0800, Patrick Mochel wrote:
> > And, appended is a patch to export PM controls for PCI devices. The file
> > "pm_possible_states" exports the states a device supports, and "pm_state"
> > exports the current state (and provides the interface for entering a
> > state).
>
> Your patch doesn't handle the PM dependencies, unfortunately...
>
> Thanks,
> Dominik

Physical power dependencies are a very bus and platform specific matter.
I don't expect to see much core level help or infustructure. I think in
the PCI case, we would first require PCI bus power management support.
This feature is currently nonexistent. As I understand, PCI express links
are capable of handling much of this at the hardware level, so it's not
especially important for newer hardware.

At the moment, I think the biggest X86 pm dependency issue is ACPI power
resources.

Logical dependencies might be another matter. For example, if we have a
bus-instance structure at the driver core level, it may make sense to
call some sort of ->prepare_for_children mechansim before starting up a
child device.

Thanks,
Adam