linux-kernel - Re: [PATCH v7] hwmon: Add driver for EXYNOS4 TMU

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Date:	Tue, 15 Nov 2011 13:24:13 -0800
From:	Guenter Roeck <guenter.roeck@...csson.com>
To:	Paul Bolle <pebolle@...cali.nl>
CC:	Donggeun Kim <dg77.kim@...sung.com>,
	"lm-sensors@...sensors.org" <lm-sensors@...sensors.org>,
	"linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
	"kyungmin.park@...sung.com" <kyungmin.park@...sung.com>,
	"myungjoo.ham@...sung.com" <myungjoo.ham@...sung.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v7] hwmon: Add driver for EXYNOS4 TMU

On Tue, 2011-11-15 at 15:34 -0500, Paul Bolle wrote:
> (This is an attempt to do a bit of review after the fact. See, this
> appears to be to the patch that ended up as commit
> 9d97e5c81e15afaef65d00f077f863c94f750839 in the mainline tree. Since
> that tree is at v3.2-rc2 now this might be in time for v3.2. If my
> comments have merit, that is.)
> 
> On Wed, 2011-09-07 at 18:49 +0900, Donggeun Kim wrote:
> > This patch allows to read temperature
> > from TMU(Thermal Management Unit) of SAMSUNG EXYNOS4 series of SoC.
> [...]
> > diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
> > index 0b62c3c..c6fb761 100644
> > --- a/drivers/hwmon/Kconfig
> > +++ b/drivers/hwmon/Kconfig
> > @@ -303,6 +303,16 @@ config SENSORS_DS1621
> >  	  This driver can also be built as a module.  If so, the module
> >  	  will be called ds1621.
> >  
> > +config SENSORS_EXYNOS4_TMU
> > +	tristate "Temperature sensor on Samsung EXYNOS4"
> > +	depends on EXYNOS4_DEV_TMU
> 
> It doesn't look like that Kconfig symbol is part of the tree just yet.
> That means people will not be able to build this driver from the
> mainline tree. Why is this dependency needed? In a (rather quick) scan
> of the code of this driver I couldn't spot anything not yet available in
> the tree.
> 
I have to defer to the driver author for that. Maybe the dependency was
renamed at some point, or removed altogether.

> > +	help
> > +	  If you say yes here you get support for TMU (Thermal Managment
> > +	  Unit) on SAMSUNG EXYNOS4 series of SoC.
> > +
> > +	  This driver can also be built as a module. If so, the module
> > +	  will be called exynos4-tmu.
> > +
> >  config SENSORS_I5K_AMB
> >  	tristate "FB-DIMM AMB temperature sensor on Intel 5000 series chipsets"
> >  	depends on PCI && EXPERIMENTAL
> [...]
> > diff --git a/drivers/hwmon/exynos4_tmu.c b/drivers/hwmon/exynos4_tmu.c
> > new file mode 100644
> > index 0000000..0170c90
> > --- /dev/null
> > +++ b/drivers/hwmon/exynos4_tmu.c
> [...]
> > +#ifdef CONFIG_PM
> > +static int exynos4_tmu_suspend(struct platform_device *pdev, pm_message_t state)
> > +{
> > +	exynos4_tmu_control(pdev, false);
> > +
> > +	return 0;
> > +}
> > +
> > +static int exynos4_tmu_resume(struct platform_device *pdev)
> > +{
> > +	exynos4_tmu_initialize(pdev);
> > +	exynos4_tmu_control(pdev, true);
> > +
> > +	return 0;
> > +}
> > +#else
> > +#define exynos4_tmu_suspend NULL
> > +#define exynos4_tmu_resume NULL
> > +#endif
> > +
> > +static struct platform_driver exynos4_tmu_driver = {
> > +	.driver = {
> > +		.name   = "exynos4-tmu",
> > +		.owner  = THIS_MODULE,
> > +	},
> > +	.probe = exynos4_tmu_probe,
> > +	.remove	= __devexit_p(exynos4_tmu_remove),
> > +	.suspend = exynos4_tmu_suspend,
> > +	.resume = exynos4_tmu_resume,
> > +};
> 
> A common idiom seems to be (I'm speaking from memory here) to
> wrap .suspend and .resume inside an "#ifdef CONFIG_PM" / "#endif" pair.
> That would allow to drop both "#define exynos4_tmu_suspend NULL" and
> "#define exynos4_tmu_resume NULL" above. Would that work here too?
> 
Seems to be a matter of opinion. I personally don't care one way or the
other, but I was told some time ago that the above method would be
preferred over using a second #ifdef.

Guenter


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