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Date: Wed, 31 Aug 2011 16:01:05 -0400
From: Vivien Didelot <vivien.didelot@savoirfairelinux.com>
To: "H. Peter Anvin" <hpa@zytor.com>
Cc: Mark Brown <broonie@opensource.wolfsonmicro.com>, x86@kernel.org,
        Jonas Fonseca <jonas.fonseca@savoirfairelinux.com>,
        Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@redhat.com>,
        linux-kernel@vger.kernel.org
Subject: Re: [v2 3/4] platform: (TS-5500) add LED support
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On Tue, 30 Aug 2011 15:04:00 -0700,
"H. Peter Anvin" <hpa@zytor.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