Re: [PATCH dt-schema] schemas: i2c: add optional GPIO binding for SMBALERT# line

[Rob Herring <robh@kernel.org>]

On Mon, Sep 9, 2024 at 8:31 AM Geert Uytterhoeven <geert@linux-m68k.org> wrote:
>
> Hi Rob,
>
> On Mon, Sep 9, 2024 at 3:07 PM Rob Herring <robh@kernel.org> wrote:
> > On Mon, Sep 9, 2024 at 5:58 AM Wolfram Sang
> > <wsa+renesas@sang-engineering.com> wrote:
> > >
> > > Most I2C controllers do not have a dedicated pin for SMBus Alerts. Allow
> > > them to define a GPIO as a side-channel.
> >
> > Most GPIOs are also interrupts, so shouldn't the existing binding be
> > sufficient? The exception is if the GPIO needs to be polled.
>
> If the GPIO pin supports multiple functions, it must be configured as
> a GPIO  first. devm_gpiod_get() takes care of that.  Just calling
> request_irq() does not.  In addition, the mapping from GPIO to IRQ
> number may not be fixed, e.g. in case the GPIO controller supports
> less interrupt inputs than GPIOs, and needs to map them when requested.

All sounds like Linux problems...

> See also the different handling of interrupts and gpios by gpio-keys.

I believe "gpios" is what was originally supported, but now it is
preferred if GPIOs are used as interrupts then we use interrupts in
DT.

Rob