Re: Nested suspends; messages vs. states

Alan Stern
2005-03-22T17:24:17Z

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On Tue, 22 Mar 2005, Pavel Machek wrote:

> And do we really want user writing D2 to /sys file?

Yes, absolutely. And we want the power/state file to contain "D2" when
a PCI device is in that state.

> > Even just from first principles the mistake is apparent. pm_message_t is
> > (or will be, when the structure is defined in its final form) a _message_,
> > not a _state_. It contains (will contain) things other than the power
> > state setting, such as the "flags" field. Why would a device want to
> > store pm_message_t.flags as part of its current state?
>
> Because device may enter different hw states for different flags?

But once the device is in a particular state, the reason why it entered
that state doesn't matter any more. Certainly it shouldn't be _part_ of
the state.

Consider this: Device states are bus- or device-specific structures, as
discussed before. But the PM core can export a set of minimal generic
state structures for use by drivers that don't need anything more
complicated than On, Frozen, or Suspended. How does that sound?

Alan Stern