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SubjectRe: NAK new drivers without proper power management?
Rafael J. Wysocki schrieb:
> I think we can introduce a "pm_safe" flag that will indicate if the driver
> handles suspend/resume correctly. If we do it, we can flag all of the drivers
> currently in the tree as "pm_safe" unless we know that they aren't. Next,
> we can convert the core to fail the suspend for any driver that is not flagged
> as "pm_safe". But I think that will take time.

Why a new flag? IMHO it would be both more readable and more efficient
to create a pm_generic_nosuspend() function which does "return -ENOSYS",
and set that as the .suspend method on drivers known to break
suspend/resume. New drivers should either have .suspend and .resume
methods of their own or set .suspend = pm_generic_nosuspend.

That way, NULL .suspend/.resume methods retain their current semantics
("don't know whether suspend would work, never thought about it"),
error-returning ones would clearly signal "cannot suspend safely", and
success-returning ones would equally clearly signal "suspend works ok".
(Bugs nonwithstanding.)

There could then be a policy parameter (Kconfig selectable to start)
to abort suspend when encountering a driver without .suspend/.resume
methods, or to proceed with a warning message.

Tilman Schmidt E-Mail:
Bonn, Germany
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