linux-kernel - Re: [PATCH] cpufreq: speedstep: remove unnecessary static in speedstep_detect

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Message-ID: <20170705101404.GA17431@isilmar-4.linta.de>
Date:   Wed, 5 Jul 2017 12:14:04 +0200
From:   Dominik Brodowski <linux@...inikbrodowski.net>
To:     Viresh Kumar <viresh.kumar@...aro.org>
Cc:     "Gustavo A. R. Silva" <garsilva@...eddedor.com>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>, linux-pm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] cpufreq: speedstep: remove unnecessary static in
 speedstep_detect_chipset()

Viresh, Gustavo,

On Wed, Jul 05, 2017 at 09:23:44AM +0530, Viresh Kumar wrote:
> + Dominic,
> 
> On 04-07-17, 22:09, Gustavo A. R. Silva wrote:
> > Remove unnecessary static on local variable hostbridge.
> > Such variable is initialized before being used,
> > on every execution path throughout the function.
> > The static has no benefit and, removing it reduces
> > the code size.
> > 
> > This issue was detected using Coccinelle and the following semantic patch:
> > 
> > @bad exists@
> > position p;
> > identifier x;
> > type T;
> > @@
> > 
> > static T x@p;
> > ...
> > x = <+...x...+>
> > 
> > @@
> > identifier x;
> > expression e;
> > type T;
> > position p != bad.p;
> > @@
> > 
> > -static
> >  T x@p;
> >  ... when != x
> >      when strict
> > ?x = e;
> > 
> > In the following log you can see the difference in the code size. Also,
> > there is a significant difference in the bss segment. This log is the
> > output of the size command, before and after the code change:
> > 
> > before:
> >    text    data     bss     dec     hex filename
> >    5084    3392     256    8732    221c drivers/cpufreq/speedstep-ich.o
> > 
> > after:
> >    text    data     bss     dec     hex filename
> >    5062    3304     192    8558    216e drivers/cpufreq/speedstep-ich.o
> > 
> > Signed-off-by: Gustavo A. R. Silva <garsilva@...eddedor.com>
> > ---
> >  drivers/cpufreq/speedstep-ich.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/drivers/cpufreq/speedstep-ich.c b/drivers/cpufreq/speedstep-ich.c
> > index b86953a..0412a24 100644
> > --- a/drivers/cpufreq/speedstep-ich.c
> > +++ b/drivers/cpufreq/speedstep-ich.c
> > @@ -207,7 +207,7 @@ static unsigned int speedstep_detect_chipset(void)
> >  		 * 8100 which use a pretty old revision of the 82815
> >  		 * host bridge. Abort on these systems.
> >  		 */
> > -		static struct pci_dev *hostbridge;
> > +		struct pci_dev *hostbridge;
> 
> This was added way back Sep'02 by Dominic (@Dominic: I hope you are the same
> Dominic with a different email id) and I don't think we need it to be static
> here. Anyway, Dominic can respond on that.
> 
> commit 1673f3b404bd ("[PATCH] CPUfreq i386 drivers update")
> 
> (Note: You can find it in history kernel git repo, not the current one).
> 
> Acked-by: Viresh Kumar <viresh.kumar@...aro.org>

indeed, that's me, and the patch seems to be valid and therefore is a useful
improvement:

Acked-by: Dominik Brodowski <linux@...inikbrodowski.net>

Thanks,
	Dominik