Re: [PATCH v3] gpio: interrupt consistency check for OF GPIO IRQs

[Gerlando Falauto <gerlando.falauto@keymile.com>]

Hi everyone,

[jumping in on an old discussion]

On 09/09/2013 06:19 PM, Mark Brown wrote:
> On Wed, Sep 04, 2013 at 02:16:36PM -0600, Stephen Warren wrote:
>> On 09/04/2013 03:05 AM, Lars Poeschel wrote:
>
>>> The driver that tries to use the GPIO requested by this patch before HAS to
>>> fail. This is exactly the intention of this patch. We don't want the GPIO to
>>> be requested any more, if it is used as an interrupt pin.
>
>> That will break existing drivers. There are drivers that request the
>> same GPIO and IRQ. IIRC, the SDHCI CD (Card Detect) GPIO is requested
>> that way.
>
> Yes, plus input devices and audio jack detection among others.  This
> pattern is very common if the GPIO is actually being used as a GPIO, an
> edge triggered interrupt is used to flag when something happens and the
> state is determined by reading the GPIO state (often with some
> debounce).

I actually came across this thread while looking for an answer to the 
following (apparently trivial) question:

If you were to write a new driver & binding, what would be, in general, 
the recommended DT binding for a cascade interrupt controller (or any 
other peripheral, for that matter), which is connected through a GPIO 
(to be used as IRQ)?

a) Through gpios = <&gpio0 N>
b) through interrupt-parent = <&gpio0> & interrupts <N 
IRQ_TYPE_LEVEL_LOW>, or
c) both?

Thanks!
Gerlando