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

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Date:	Tue, 30 Aug 2011 17:14:24 -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 Mon, 29 Aug 2011 22:37:53 -0700,
"H. Peter Anvin" <hpa@...or.com> wrote:

> On 08/29/2011 03:16 PM, Mark Brown wrote:
> > On Fri, Aug 26, 2011 at 07:40:26PM -0400, Vivien Didelot wrote:
> > 
> >> +static void ts5500_led_work(struct work_struct *work)
> >> +{
> >> +	struct ts5500_led *led = container_of(work, struct
> >> ts5500_led, work);
> >> +	u8 val = led->new_brightness ? led->bit : 0;
> >> +
> >> +	outb(val, led->ioaddr);
> >> +}
> > 
> > Can you not do outb() from atomic context?  The reason lots of LED
> > drivers update the hardware in a workqueue is that they communicate
> > with the hardware over buses that can't be used in atomic context
> > like I2C or SPI but if that's not an issue then the workqueue is
> > not required and the code can be simplified.
> 
> outb() can definitely be executed from atomic context.
> 
> 	-hpa

Good to know, thanks. I removed the work_struct and instead lock a mutex
before setting led->new_brightness and calling outb().

	Vivien.
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