Re: [PATCH v2 1/2] dt-bindings: gpio: add gpio-aggregator binding

[James Hilliard]

On Wed, Feb 11, 2026 at 1:26 AM Geert Uytterhoeven <geert@xxxxxxxxxxxxxx> wrote:
>
> Hi James,
>
> On Wed, 11 Feb 2026 at 09:14, James Hilliard <james.hilliard1@xxxxxxxxx> wrote:
> > Document the gpio-aggregator virtual GPIO controller with a dedicated
> > schema and compatible string.
> >
> > Also extend the GPIO AGGREGATOR MAINTAINERS entry to cover the new
> > binding file.
> >
> > Signed-off-by: James Hilliard <james.hilliard1@xxxxxxxxx>
>
> Thanks for your patch!
>
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/gpio/gpio-aggregator.yaml
> > @@ -0,0 +1,54 @@
> > +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> > +%YAML 1.2
> > +---
> > +$id: http://devicetree.org/schemas/gpio/gpio-aggregator.yaml#
> > +$schema: http://devicetree.org/meta-schemas/core.yaml#
> > +
> > +title: GPIO aggregator controller
> > +
> > +maintainers:
> > +  - Alexander Stein <linux@xxxxxxxxxxxxxxx>
> > +
> > +description:
> > +  GPIO aggregator forwards selected GPIO lines from one or more GPIO
> > +  controllers and exposes them as a virtual GPIO controller.
>
> > +examples:
> > +  - |
> > +    #include <dt-bindings/gpio/gpio.h>
> > +
> > +    gpio_agg: gpio-aggregator {
> > +        compatible = "gpio-aggregator";
> > +        #gpio-cells = <2>;
> > +        gpio-controller;
> > +        gpios = <&gpio0 3 GPIO_ACTIVE_LOW>,
> > +                <&gpio3 1 GPIO_ACTIVE_HIGH>;
> > +        gpio-line-names = "modem-reset", "modem-enable";
> > +    };
>
> Looking at the example, it seems you intend to use the gpio-aggregator
> as a "Generic GPIO Driver", like in the example in the documentation[1].
> Hence I think you should not introduce and abuse the "gpio-aggregator"
> compatible value for this, but instead:
>   1. Use a proper compatible value that matches your device,
>   2. Write proper DT bindings for the device,
>   3. Add the proper device's compatible value to the gpio-aggregator
>      driver's match table.
> The above is very similar to how spidev is handled, which also forbids
> using the spidev compatible value in DTS.

Isn't this gpio-aggregator driver supposed to be non-hardware
specific?

I'm trying to use it as described here, I noticed the compatible
in the blog post was missing and just needed adding to the
driver: https://bootlin.com/blog/gpio-aggregator-a-virtual-gpio-chip/

> [1] https://docs.kernel.org/6.2/admin-guide/gpio/gpio-aggregator.html#generic-gpio-driver
> [2] https://docs.kernel.org/spi/spidev.html
>
> Gr{oetje,eeting}s,
>
>                         Geert
>
> --
> Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx
>
> In personal conversations with technical people, I call myself a hacker. But
> when I'm talking to journalists I just say "programmer" or something like that.
>                                 -- Linus Torvalds