linux-kernel - Re: [PATCH 2/5] dt-bindings: gpio: gpio-thunderx: Describe pin-cfg option

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Date:   Mon, 2 May 2022 00:15:34 +0200
From:   Linus Walleij <linus.walleij@...aro.org>
To:     Piyush Malgujar <pmalgujar@...vell.com>
Cc:     linux-gpio@...r.kernel.org, linux-kernel@...r.kernel.org,
        devicetree@...r.kernel.org, brgl@...ev.pl, robh+dt@...nel.org,
        krzysztof.kozlowski+dt@...aro.org, rric@...nel.org,
        cchavva@...vell.com, wsadowski@...vell.com
Subject: Re: [PATCH 2/5] dt-bindings: gpio: gpio-thunderx: Describe pin-cfg option

On Wed, Apr 27, 2022 at 4:47 PM Piyush Malgujar <pmalgujar@...vell.com> wrote:

> Add support for pin-cfg to configure GPIO Pins
>
> Signed-off-by: Piyush Malgujar <pmalgujar@...vell.com>
> ---
>  Documentation/devicetree/bindings/gpio/gpio-thunderx.txt | 4 ++++

Would be nice to rewrite this binding in YAML

>    - First cell is the GPIO pin number relative to the controller.
>    - Second cell is triggering flags as defined in interrupts.txt.
> +- pin-cfg: Configuration of pin's function, filters, XOR and output mode.
> +  - First cell is the GPIO pin number
> +  - Second cell is a value written to GPIO_BIT_CFG register at driver probe.

Just poking magic hex values into some random register as
part of a binding is not a good idea.

This looks like trying to reinvent the pin config subsystem.

GPIO is using the standard pin configurations in the second cell of
the handle, use them in this driver as well and add new ones if we
need.

You find the existing flags here:
include/dt-bindings/gpio/gpio.h

If you need something more sophisticated than a simple flag, I think
you need to implement proper pin config.

Yours,
Linus Walleij