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

[Geert Uytterhoeven]

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.

[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