linux-kernel - Re: [PATCH 4/4][update] hwmon / exynos4_tmu: Use struct dev_pm

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Date:	Sun, 8 Jul 2012 21:42:35 -0700
From:	Guenter Roeck <linux@...ck-us.net>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Linux PM list <linux-pm@...r.kernel.org>,
	Hans de Goede <hdegoede@...hat.com>,
	Alistair John Strachan <alistair@...zero.co.uk>,
	lm-sensors@...sensors.org, Jean Delvare <khali@...ux-fr.org>,
	Kukjin Kim <kgene.kim@...sung.com>
Subject: Re: [PATCH 4/4][update] hwmon / exynos4_tmu: Use struct dev_pm_ops
 for power management

On Sun, Jul 08, 2012 at 10:46:12PM +0200, Rafael J. Wysocki wrote:
> On Sunday, July 08, 2012, Guenter Roeck wrote:
> > On Sun, Jul 08, 2012 at 09:48:15PM +0200, Rafael J. Wysocki wrote:
> > > From: Rafael J. Wysocki <rjw@...k.pl>
> > > 
> > Hi Rafael,
> > 
> > > Make the Exynos4 TMU driver define its PM callbacks through
> > > a struct dev_pm_ops object rather than by using legacy PM hooks
> > > in struct platform_driver.
> > > 
> > > Signed-off-by: Rafael J. Wysocki <rjw@...k.pl>
> > > ---
> > >  drivers/hwmon/exynos4_tmu.c |   18 +++++++++++-------
> > >  1 file changed, 11 insertions(+), 7 deletions(-)
> > > 
> > > Index: linux/drivers/hwmon/exynos4_tmu.c
> > > ===================================================================
> > > --- linux.orig/drivers/hwmon/exynos4_tmu.c
> > > +++ linux/drivers/hwmon/exynos4_tmu.c
> > > @@ -476,34 +476,38 @@ static int __devexit exynos4_tmu_remove(
> > >  }
> > >  
> > >  #ifdef CONFIG_PM
> > > -static int exynos4_tmu_suspend(struct platform_device *pdev, pm_message_t state)
> > > +static int exynos4_tmu_suspend(struct device *dev)
> > >  {
> > > -	exynos4_tmu_control(pdev, false);
> > > +	exynos4_tmu_control(to_platform_device(dev), false);
> > >  
> > >  	return 0;
> > >  }
> > >  
> > > -static int exynos4_tmu_resume(struct platform_device *pdev)
> > > +static int exynos4_tmu_resume(struct device *dev)
> > >  {
> > > +	struct platform_device *pdev = to_platform_device(dev);
> > > +
> > >  	exynos4_tmu_initialize(pdev);
> > >  	exynos4_tmu_control(pdev, true);
> > >  
> > >  	return 0;
> > >  }
> > > +
> > > +static SIMPLE_DEV_PM_OPS(exynos4_tmu_pm,
> > > +			 exynos4_tmu_suspend, exynos4_tmu_resume);
> > > +#define EXYNOS4_TMU_PM	(&exynos4_tmu_pm)
> > >  #else
> > > -#define exynos4_tmu_suspend NULL
> > > -#define exynos4_tmu_resume NULL
> > > +#define EXYNOS4_TMU_PM	NULL
> > >  #endif
> > 
> > Actually, looking into other drivers, the common approach seems to be to declare
> > 
> > static SIMPLE_DEV_PM_OPS(exynos4_tmu_pm,
> > 			 exynos4_tmu_suspend, exynos4_tmu_resume);
> > 
> > outside the #ifdef code and then just assign
> > 
> > 		.pm = &exynos4_tmu_pm;
> > 
> > unconditionally.
> > 
> > That seems to be a much simpler solution. Any special reason for not
> > implementing it this way ? Same question applies to the other patches in the
> > series.
> 
> In fact, there are two ways.  One of them is what you said, the other is to
> put SIMPLE_DEV_PM_OPS() under the #ifdef like I did.  I'm not sure which one
> is prevalent, but what I did has the advatnage that the kernel data will
> be slightly smaller if CONFIG_PM is unset.
> 
Ok, make sense. Applied to -next.

Thanks,
Guenter
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