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From: "Rafael J. Wysocki" <rjw@sisk.pl>
To: Alan Stern <stern@rowland.harvard.edu>
Subject: Re: [RFD] Automatic suspend
Date: Tue, 17 Feb 2009 00:02:36 +0100
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On Monday 16 February 2009, Alan Stern wrote:
> On Mon, 16 Feb 2009, Rafael J. Wysocki wrote:
> 
> > OK, so I think there are two things that user space may be allowed to do as
> > far as putting devices into low power states is concerned:
> > * disable/enable the automatic power management of the device (provided that
> >   the driver supports the automatic PM)
> 
> Set the automatic PM parameters (idle timeout, state to go to, etc.).  

Yes.  I'm not sure about the state part, though.

> And disabling automatic PM altogether (effectively the same as setting
> the idle timeout to infinity).

Yes.

> > * check what power states devices are in.
> 
> What about situations where we want to distinguish between the power 
> state of the device itself and the power state of the link?  For a disk 
> drive we may want to power the link on and off quite a lot, as that 
> has low latency, but spinning the disk up and down takes a long time 
> and so should have a longer idle-time value.

Well, I'm not sure at the moment.

Do you have any suggestions?

Rafael