linux-kernel - Re: [v2 3/4] platform: (TS-5500) add LED support

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Date:	Wed, 31 Aug 2011 16:01:05 -0400
From:	Vivien Didelot <vivien.didelot@...oirfairelinux.com>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	Mark Brown <broonie@...nsource.wolfsonmicro.com>, x86@...nel.org,
	Jonas Fonseca <jonas.fonseca@...oirfairelinux.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>, linux-kernel@...r.kernel.org
Subject: Re: [v2 3/4] platform: (TS-5500) add LED support

On Tue, 30 Aug 2011 15:04:00 -0700,
"H. Peter Anvin" <hpa@...or.com> wrote:

> On 08/30/2011 02:56 PM, Vivien Didelot wrote:
> >>
> > I wrote the led_set function like:
> > 
> >   static void ts5500_led_set(struct led_classdev *led_cdev,
> >                              enum led_brightness value)
> >   {
> >           struct ts5500_led *led = container_of(led_cdev,
> >                                                 struct ts5500_led,
> >                                                 cdev);
> >           mutex_lock(&led->lock);
> >           led->new_brightness = (value == LED_OFF) ? LED_OFF :
> > LED_FULL; outb(value, led->ioaddr);
> >           mutex_unlock(&led->lock);
> >   }
> > 
> > I guess the wrong value could be read if we get preempted just
> > before the outb() call, am I wrong?
> > 
> 
> And what happens if we do?
> 
> P.S. Your canonicalization of the value doesn't extend to outb().
> 
> 	-hpa

In fact the new_brightness field wasn't necessary in this driver, so I
removed it and now the function only contains the outb() call. Thanks.

	Vivien
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