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

From: Rafael J. Wysocki
Date: Sun Jan 30 2011 - 17:40:17 EST

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?

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