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

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Message-Id: <201101302339.02993.rjw@sisk.pl>
Date:	Sun, 30 Jan 2011 23:39:02 +0100
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Alan Stern <stern@...land.harvard.edu>
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 Sunday, January 30, 2011, Alan Stern wrote:
> 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?

That certainly is a good idea, but I wasn't sure how to do that.  It looks
like I could keep the __weak functions as they are and modify
platform_dev_pm_ops instead to point to a new set of function that in turn
would call the __weak ones.  For example, the .suspend pointer in
platform_dev_pm_ops might point to a new function, say
platform_pm_full_suspend() that would call the power domain functions and
the "original" platform_pm_suspend().  Is that what you mean?

Rafael
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