Subject: Re: [eman] iana powerstate tc proposal

From: Juergen Schoenwaelder <[email-masked]>
Date: Fri, 2 Sep 2011 17:42:40 +0200

On Mon, Aug 15, 2011 at 01:40:12PM -0500, Mielke, William F (Bill) wrote:
> > But your design aims at reporting a certain true state of the device
> > according to different sets concurrently - so you assume there is a
> > translation which is implementation dependent, that is every device
> > can translate as it likes to do it. Not sure how this really helps
> > with interoperability. (And the same goes to proposals where the power
> > states are expected to be a series with 1000 as percentage increments
> > as mentioned previously - this looks to me like a fine grained control
> > knob and not a power state.)
> > 
> > /js
> > 
> > -- 
> > Juergen Schoenwaelder           Jacobs University Bremen gGmbH
> 
> From my perspective allowing for a given device to support multiple power state sets simultaneously we are improving/enabling increased interoperability by allowing the EnMS interact with the device using it's preferred power state set.  Some EnMS may only support a single power state set, for example, so allowing the device to support multiple power state sets increases the number of EnMS which can interoperate with the device.
> 
> Regarding the "magic" mapping between the power states within the various sets supported by a device, the core assumption (perhaps this needs to be made explicit) is that if a device chooses to support multiple power state sets that it must do so in such a way that the device operates in a sensible manner within the individual contexts of each power state set it supports.  It is impossible to define a universally applicable mapping for this but within the context of a given device a sensible mapping may certainly be possible.  If it is, then the device can choose to support that mapping and the various EnMS can safely interact with it using any of the available power state sets.

It is kind of interesting to hear that dealing with multiple power
state sets is too hard for an EnMS but that this is an easily solvable
problem for devices and that relying on an implementation specific
"sensible mapping" provided by devices (which can be different for
different devices and manufacturers) is sufficient to build robust
EnMS.

But the question we were discussing here (see the quoted text above)
is whether device are expected to report and act according to multiple
different power state sets _concurrently_. Are you saying this is the
case since devices may need to talk to different EnMS at the same time
and these different EnMS all have a simplified view of world where
there is only one set of power states?

/js

-- 
Juergen Schoenwaelder           Jacobs University Bremen gGmbH
Phone: +49 421 200 3587         Campus Ring 1, 28759 Bremen, Germany
Fax:   +49 421 200 3103         <http://www.jacobs-university.de/>