linux-kernel - Re: [PATCH RFC v2 4/7] pinctrl-scmi: add PIN_CONFIG_INPUT

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Message-ID: <CACRpkdY3_ifPsQOTqa2e-kHR24Khy0axrZ=K+vO4OJB+FjdB2A@mail.gmail.com>
Date: Fri, 5 Sep 2025 10:31:30 +0200
From: Linus Walleij <linus.walleij@...aro.org>
To: Dan Carpenter <dan.carpenter@...aro.org>
Cc: Sudeep Holla <sudeep.holla@....com>, AKASHI Takahiro <takahiro.akashi@...aro.org>, 
	Michal Simek <michal.simek@....com>, Cristian Marussi <cristian.marussi@....com>, 
	arm-scmi@...r.kernel.org, linux-arm-kernel@...ts.infradead.org, 
	linux-gpio@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH RFC v2 4/7] pinctrl-scmi: add PIN_CONFIG_INPUT_VALUE

On Fri, Sep 5, 2025 at 10:27 AM Linus Walleij <linus.walleij@...aro.org> wrote:
> On Sun, Jul 20, 2025 at 9:39 PM Dan Carpenter <dan.carpenter@...aro.org> wrote:
>
> > In SCMI the value of the pin is just another configuration option.  Add
> > this as an option in the pin_config_param enum and creating a mapping to
> > SCMI_PIN_INPUT_VALUE in pinctrl_scmi_map_pinconf_type()
> >
> > Since this is an RFC patch, I'm going to comment that I think the SCMI
> > pinctrl driver misuses the PIN_CONFIG_OUTPUT enum.  It should be for
> > enabling and disabling output on pins which can serve as both input and
> > output.  Enabling it is supposed to write a 1 and disabling it is
> > supposed to write a 0 but we use that side effect to write 1s and 0s.  I
> > did't change this because it would break userspace but I'd like to add a
> > PIN_CONFIG_OUTPUT_VALUE enum as well and use that in the GPIO driver.
> > But in this patchset I just use PIN_CONFIG_OUTPUT.
> >
> > Signed-off-by: Dan Carpenter <dan.carpenter@...aro.org>
>
> I tweaked this patch around a bit and applied: removed the second comment
> in the commit message and wrote the docs to be more generic since
> in the future other things than SCMI might want to use this
> config option.

Then I thought about it some more. ...

Isn't it more intuitive that we rewrite the curren PIN_CONFIG_OUTPUT_VALUE
to just PIN_CONFIG_VALUE that can be used for both reading and
writing binary low/high instead of having two different things like this?

I will look over current users and maybe propose a patch.

Yours,
Linus Walleij