Re: [PATCH v2] gpio: interrupt consistency check for OF GPIO IRQs

Linus Walleij
2013-08-23T18:45:51Z

On Thu, Aug 22, 2013 at 11:10 PM, Stephen Warren <swarren@wwwdotorg.org> wrote:
> On 08/21/2013 05:36 PM, Linus Walleij wrote:
>> On Thu, Aug 22, 2013 at 1:10 AM, Stephen Warren <swarren@wwwdotorg.org> wrote:
>> [Me]
>>>>> check if these in turn reference the interrupt-controller, and
>>>>> if they do, loop over the interrupts used by that child and
>>>>> perform gpio_request() and gpio_direction_input() on these,
>>>>> making them unreachable from the GPIO side.
>>>
>>> What about bindings that require a GPIO to be specified, yet don't allow
>>> an IRQ to be specified, and the driver internally does perform
>>> gpio_to_irq() on it? I don't think one can detect that case.
>>
>> This is still allowed. Consumers that prefer to have a GPIO
>> passed and convert it to IRQ by that call can still do so,
>> they will know what they're doing and will not cause the
>> double-command situation that we're trying to solve.
>
> Why not? There are certainly drivers in the kernel which request a GPIO
> as both a GPIO and as an (dual-edge) interrupt, so that they can read
> the GPIO input whenever the IRQ goes off, in order to determine the pin
> state. This is safer against high-latency or lost interrupts.

Yes? Are we talking past each other here?

This is a perfectly OK thing to do as long as it is done like
this:

request_gpio(gpio);
gpio_direction_input(gpio);
request_irq(gpio_to_irq(gpio));

Pass only the GPIO in the device tree and this works just fine.

The use case after that we do not interfer with.

Yours,
Linus Walleij