linux-kernel - Re: I2c GPIO Recovery with pinctrl strict mode

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Message-ID: <CACRpkdaKYN9eRtuOhBBp_50sR71AQvNSKtjAR1RZPhaKYhfJVw@mail.gmail.com>
Date:   Mon, 13 Feb 2023 10:29:48 +0100
From:   Linus Walleij <linus.walleij@...aro.org>
To:     Ryan.Wanner@...rochip.com
Cc:     linux-i2c@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-gpio@...r.kernel.org, alexandre.belloni@...tlin.com,
        Ludovic.Desroches@...rochip.com, Nicolas.Ferre@...rochip.com,
        Claudiu.Beznea@...rochip.com
Subject: Re: I2c GPIO Recovery with pinctrl strict mode

On Fri, Feb 10, 2023 at 4:21 PM <Ryan.Wanner@...rochip.com> wrote:

> I am trying to enable .strict in the Atmel pinctrl driver, and that is
> what is causing my issues.

Strictly speaking (ha!) that flag is for when you *cannot* use a pin
in GPIO mode at the same time as another mode.

Example: if you use the pin in I2C mode, then reading the GPIO
input register will *not* reflect the value on the electrical line,
because it has been decoupled physically. Then .strict should
be true.

The strict mode was not intended for policy, i.e. stopping kernel
developers from doing wrong things. They have enough tools to
do wrong things anyway, one more or less doesn't matter.

Yours,
Linus Walleij