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

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Date:	Mon, 29 Aug 2011 22:37:53 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Mark Brown <broonie@...nsource.wolfsonmicro.com>
CC:	Vivien Didelot <vivien.didelot@...oirfairelinux.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 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
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