Re: [PATCH v1 3/8] dt-bindings: pinctrl: add NXP MC33978/MC34978 pinctrl

[Linus Walleij]

Hi Oleksij,

thanks for your patch for this very interesting hardware!

On Wed, Feb 25, 2026 at 6:16 PM Oleksij Rempel <o.rempel@xxxxxxxxxxxxxx> wrote:

> Add device tree binding documentation for the pin control and GPIO block
> of the NXP MC33978/MC34978 Multiple Switch Detection Interface (MSDI).
>
> This block manages 22 switch detection inputs (14 Switch-to-Ground,
> 8 Programmable) and acts as a GPIO controller.
>
> Additionally, it supports pin configuration for hardware-specific features
> required for long-term contact maintenance in harsh environments, such as
> adjusting the continuous/pulsed wetting current to penetrate oxide layers
> on mechanical switches.
>
> Signed-off-by: Oleksij Rempel <o.rempel@xxxxxxxxxxxxxx>

Are the hardware-specific pin configurations for oxide layer
penetration (!) and stuff excluded from these bindings? (It looks
like.)

> +++ b/Documentation/devicetree/bindings/pinctrl/nxp,mc33978-pinctrl.yaml
> @@ -0,0 +1,66 @@
> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/pinctrl/nxp,mc33978-pinctrl.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: NXP MC33978/MC34978 Pinctrl/GPIO Driver
> +
> +maintainers:
> +  - David Jander <david@xxxxxxxxxxx>
> +  - Oleksij Rempel <o.rempel@xxxxxxxxxxxxxx>
> +
> +description: |
> +  Pin control and GPIO driver for the MC33978/MC34978 MSDI device.
> +
> +  Pin numbering:
> +  - Pins 0-13: SG0-SG13 (Switch-to-Ground inputs)

I don't know what a switch-to-ground input is, but I talked to an AI
about it.

It appears to be directly incorrect to use such a line without
flagging it as GPIO_ACTIVE_LOW in the consumer so this should
be mentioned here, GPIO lines 0-13 *must* be flagged
GPIO_ACTIVE_LOW. (I don't know a good way to enforce it
in schema, sadly, maybe Conor has ideas.)

> +  - Pins 14-21: SP0-SP7 (Programmable inputs, can be SG or SB)

What is SB now? Please explain :)

Other than that it looks good to me!

Yours,
Linus Walleij