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

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Date:	Mon, 31 Jan 2011 14:45:33 -0500 (EST)
From:	Alan Stern <stern@...land.harvard.edu>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
cc:	Magnus Damm <magnus.damm@...il.com>,
	Linux-pm mailing list <linux-pm@...ts.linux-foundation.org>,
	Greg KH <greg@...ah.com>, LKML <linux-kernel@...r.kernel.org>,
	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 Mon, 31 Jan 2011, Rafael J. Wysocki wrote:

> On Monday, January 31, 2011, Alan Stern wrote:
> > On Sun, 30 Jan 2011, Rafael J. Wysocki wrote:
> > 
> > > > 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?
> > 
> > Yes.  But what about the platform_bus_set_pm_ops() interface?  Should
> > platform-specific replacements for the pm_ops functions also include
> > the power_domain callbacks?
> 
> Well, whoever uses platform_bus_set_pm_ops(), he can simply prevent power
> domains from being used by not defining them in the first place. :-)

But what about the case where the user _does_ want to have power
domains?  Do you want to make the replacement routines responsible for
invoking the power-domain callbacks, or should the platform core handle
this automatically?

Alan Stern

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