Re: [v2 2/4] platform: (TS-5500) add GPIO support

H. Peter Anvin
2011-08-30T18:44:30Z

On 08/30/2011 11:39 AM, Vivien Didelot wrote:
> On Mon, 29 Aug 2011 23:11:33 +0100,
> Mark Brown <broonie@opensource.wolfsonmicro.com> wrote:
>> On Fri, Aug 26, 2011 at 07:40:25PM -0400, Vivien Didelot wrote:
>>> + bitno = line_to_bit_map[offset];
>>> +
>>> + mutex_lock(&drvdata->gpio_lock);
>>> + byte = inb(ioaddr);
>>> + mutex_unlock(&drvdata->gpio_lock);
>>
>> Do you really need the lock to do a read?
>
> Is there any chance for this function to be preempted before reading the
> register, allowing a call to ts5500_gpio_direction_output to occur
> before ts5500_gpio_get is completed?
>

Wrapping an atomic operation in a mutex makes no sense no matter how you
slice it...

-hpa