linux-kernel - Re: [RFC][PATCH] Power domains for platform bus type

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Message-ID: <Pine.LNX.4.44L0.1101301100090.6500-100000@netrider.rowland.org>
Date:	Sun, 30 Jan 2011 11:03:31 -0500 (EST)
From:	Alan Stern <stern@...land.harvard.edu>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
cc:	Linux-pm mailing list <linux-pm@...ts.linux-foundation.org>,
	Greg KH <greg@...ah.com>, LKML <linux-kernel@...r.kernel.org>,
	Magnus Damm <magnus.damm@...il.com>,
	Kevin Hilman <khilman@...com>,
	Grant Likely <grant.likely@...retlab.ca>,
	Len Brown <lenb@...nel.org>
Subject: Re: [RFC][PATCH] Power domains for platform bus type

On Sun, 30 Jan 2011, Rafael J. Wysocki wrote:

> Hi,
> 
> This is something we discussed during the last Linux Plumbers Conference.
> 
> The problem appears to be that the same device may be used in different
> systems in different configurations such that actions necessary for the
> device's power management can vary from one system to another.  In those
> cases the drivers' power management callbacks are generally not sufficient,
> because they can't take the configuration of the whole system into account.
> 
> I think this issue may be addressed by adding objects that will represent
> power domains and will provide power management callbacks to be executed
> in addition to the device driver's PM callbacks, which is done by the patch
> below.
> 
> Please have a look at it and tell me what you think.

One thing about this implementation is slightly questionable.  The new
power_domain callbacks were added to the __weak platform PM routines,
which means they will have to be included in every overriding routine
provided by a platform imiplementation.

Would it be better to separate these things?  Have the power_domain 
callbacks occur in a static outer function which then calls a public 
__weak inner function that can be overridden?

Alan Stern


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