linux-kernel - Re: [PATCH] PM: Make system-wide PM and runtime PM treat subsystems consistently

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Message-ID: <20110218192241.GA6172@kroah.com>
Date:	Fri, 18 Feb 2011 11:22:41 -0800
From:	Greg KH <greg@...ah.com>
To:	"R. J. Wysocki" <Rafal.Wysocki@....edu.pl>
Cc:	Alan Stern <stern@...land.harvard.edu>,
	Linux-pm mailing list <linux-pm@...ts.linux-foundation.org>,
	Kevin Hilman <khilman@...com>,
	Grant Likely <grant.likely@...retlab.ca>,
	LKML <linux-kernel@...r.kernel.org>,
	Magnus Damm <magnus.damm@...il.com>,
	Len Brown <lenb@...nel.org>,
	Mark Brown <broonie@...nsource.wolfsonmicro.com>
Subject: Re: [PATCH] PM: Make system-wide PM and runtime PM treat
 subsystems consistently

On Fri, Feb 18, 2011 at 12:54:25AM +0100, R. J. Wysocki wrote:
> From: Rafael J. Wysocki <rjw@...k.pl>
> 
> The code handling system-wide power transitions (eg. suspend-to-RAM)
> can in theory execute callbacks provided by the device's bus type,
> device type and class in each phase of the power transition.  In
> turn, the runtime PM core code only calls one of those callbacks at
> a time, preferring bus type callbacks to device type or class
> callbacks and device type callbacks to class callbacks.
> 
> It seems reasonable to make them both behave in the same way in that
> respect.  Moreover, even though a device may belong to two subsystems
> (eg. bus type and device class) simultaneously, in practice power
> management callbacks for system-wide power transitions are always
> provided by only one of them (ie. if the bus type callbacks are
> defined, the device class ones are not and vice versa).  Thus it is
> possible to modify the code handling system-wide power transitions
> so that it follows the core runtime PM code (ie. treats the
> subsystem callbacks as mutually exclusive).
> 
> On the other hand, the core runtime PM code will choose to execute,
> for example, a runtime suspend callback provided by the device type
> even if the bus type's struct dev_pm_ops object exists, but the
> runtime_suspend pointer in it happens to be NULL.  This is confusing,
> because it may lead to the execution of callbacks from different
> subsystems during different operations (eg. the bus type suspend
> callback may be executed during runtime suspend of the device, while
> the device type callback will be executed during system suspend).
> 
> Make all of the power management code treat subsystem callbacks in
> a consistent way, such that:
> (1) If the device's type is defined (eg. dev->type is not NULL)
>     and its pm pointer is not NULL, the callbacks from dev->type->pm
>     will be used.
> (2) If dev->type is NULL or dev->type->pm is NULL, but the device's
>     class is defined (eg. dev->class is not NULL) and its pm pointer
>     is not NULL, the callbacks from dev->class->pm will be used.
> (3) If dev->type is NULL or dev->type->pm is NULL and dev->class is
>     NULL or dev->class->pm is NULL, the callbacks from dev->bus->pm
>     will be used provided that both dev->bus and dev->bus->pm are
>     not NULL.
> 
> Signed-off-by: Rafael J. Wysocki <rjw@...k.pl>
> Acked-by: Kevin Hilman <khilman@...com>
> Reasoning-sounds-sane-to: Grant Likely <grant.likely@...retlab.ca>

Acked-by: Greg Kroah-Hartman <gregkh@...e.de>

You are going to take this through your tree, right?

thanks,

greg k-h
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