linux-kernel - Re: [PATCH 06/10] thermal: exynos: remove redundant threshold_code checks from exynos_tmu

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Date:	Thu, 15 May 2014 18:56:55 +0200
From:	Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>
To:	Eduardo Valentin <edubezval@...il.com>
Cc:	Eduardo Valentin <eduardo.valentin@...com>,
	Zhang Rui <rui.zhang@...el.com>,
	Amit Daniel Kachhap <amit.daniel@...sung.com>,
	Tomasz Figa <t.figa@...sung.com>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Kyungmin Park <kyungmin.park@...sung.com>,
	linux-samsung-soc@...r.kernel.org, linux-pm@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 06/10] thermal: exynos: remove redundant threshold_code
 checks from exynos_tmu_initialize()

On Thursday, May 15, 2014 10:55:52 AM Eduardo Valentin wrote:
> Hello Bartlomiej,

Hi,

> On Mon, May 05, 2014 at 01:15:35PM +0200, Bartlomiej Zolnierkiewicz wrote:
> > Remove runtime checks for negative return values of temp_to_code()
> > from exynos_tmu_initialize().  The current level temperature data
> > hardcoded in pdata will never cause a negative temp_to_code()
> > return values and for the new code potential mistakes should be
> > caught during development/review phases.
> > 
> > Theres should be no functional changes caused by this patch.
> > 
> 
> Same question as in previous patch. Removing defensive code must

Simirarly like in a previous case.  Such verification should not be done
at runtime in a production code because it is already too late for such
checking.  It should be done during development and review phases.

> be done carefully. 

BTW In case of temp_to_code() its users should be audited to pass only
input values that give positive results and later the function itself
may be modified to catch wrong input values by using WARN_ON (or even
BUG_ON).

> > Signed-off-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>
> > ---
> >  drivers/thermal/samsung/exynos_tmu.c | 16 +---------------
> >  1 file changed, 1 insertion(+), 15 deletions(-)
> > 
> > diff --git a/drivers/thermal/samsung/exynos_tmu.c b/drivers/thermal/samsung/exynos_tmu.c
> > index 789d745..a415829 100644
> > --- a/drivers/thermal/samsung/exynos_tmu.c
> > +++ b/drivers/thermal/samsung/exynos_tmu.c
> > @@ -170,10 +170,6 @@ static int exynos_tmu_initialize(struct platform_device *pdev)
> >  	if (data->soc == SOC_ARCH_EXYNOS4210) {
> >  		/* Write temperature code for threshold */
> >  		threshold_code = temp_to_code(data, pdata->threshold);
> > -		if (threshold_code < 0) {
> > -			ret = threshold_code;
> > -			goto out;
> > -		}
> >  		writeb(threshold_code,
> >  			data->base + reg->threshold_temp);
> >  		for (i = 0; i < trigger_levs; i++)
> > @@ -187,18 +183,12 @@ static int exynos_tmu_initialize(struct platform_device *pdev)
> >  		i < trigger_levs && i < EXYNOS_MAX_TRIGGER_PER_REG; i++) {
> >  			threshold_code = temp_to_code(data,
> >  						pdata->trigger_levels[i]);
> > -			if (threshold_code < 0) {
> > -				ret = threshold_code;
> > -				goto out;
> > -			}
> >  			rising_threshold |= threshold_code << 8 * i;
> >  			if (pdata->threshold_falling) {
> >  				threshold_code = temp_to_code(data,
> >  						pdata->trigger_levels[i] -
> >  						pdata->threshold_falling);
> > -				if (threshold_code > 0)
> > -					falling_threshold |=
> > -						threshold_code << 8 * i;
> > +				falling_threshold |= threshold_code << 8 * i;
> >  			}
> >  		}
> >  
> > @@ -217,10 +207,6 @@ static int exynos_tmu_initialize(struct platform_device *pdev)
> >  				(pdata->trigger_type[i] == HW_TRIP)) {
> >  			threshold_code = temp_to_code(data,
> >  						pdata->trigger_levels[i]);
> > -			if (threshold_code < 0) {
> > -				ret = threshold_code;
> > -				goto out;
> > -			}
> >  			if (i == EXYNOS_MAX_TRIGGER_PER_REG - 1) {
> >  				/* 1-4 level to be assigned in th0 reg */
> >  				rising_threshold |= threshold_code << 8 * i;

Best regards,
--
Bartlomiej Zolnierkiewicz
Samsung R&D Institute Poland
Samsung Electronics

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