linux-kernel - Re: [PATCH v2 2/4] Documentation: DT: bindings: input: Add documentation for cyttsp5

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Date:   Thu, 11 Nov 2021 16:16:37 +0100
From:   Linus Walleij <linus.walleij@...aro.org>
To:     Andreas Kemnade <andreas@...nade.info>
Cc:     Alistair Francis <alistair23@...il.com>,
        Alistair Francis <alistair@...stair23.me>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        devicetree <devicetree@...r.kernel.org>,
        linux-input <linux-input@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Mylene Josserand <mylene.josserand@...e-electrons.com>,
        Henrik Rydberg <rydberg@...math.org>,
        Dmitry Torokhov <dmitry.torokhov@...il.com>,
        Rob Herring <robh+dt@...nel.org>
Subject: Re: [PATCH v2 2/4] Documentation: DT: bindings: input: Add
 documentation for cyttsp5

On Wed, Nov 10, 2021 at 6:37 PM Andreas Kemnade <andreas@...nade.info> wrote:
> Alistair Francis <alistair23@...il.com> wrote:

> You have a kind of double inversion here, so things are automagically fixed.
> IMHO to describe it correctly would be to set GPIO_ACTIVE_LOW here
> and in the driver
>
>         /* Reset the gpio to be in a reset state */
>         ts->reset_gpio = devm_gpiod_get_optional(dev, "reset", GPIOD_OUT_HIGH);
>         if (IS_ERR(ts->reset_gpio)) {
>                 rc = PTR_ERR(ts->reset_gpio);
>                 dev_err(dev, "Failed to request reset gpio, error %d\n", rc);
>                 return rc;
>         }
>         gpiod_set_value(ts->reset_gpio, 0);
>
> That is the way how other active-low reset lines are handled.

Correct.

This is a source of confusion, I contemplated just changing the name
of GPIOD_OUT_HIGH to GPIOD_OUT_ASSERTED etc to indicate
what is going on.

gpiod_set_value(ts->reset_gpio, 0) should similarly be interpreted
as "de-assert this line" no matter the polarity.

Yours,
Linus Walleij