linux-kernel - Re: [PATCH v2 1/9] Documentation: gpio: add chardev userspace API documentation

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Message-ID: <CAHp75Vc=oZK=VR6vZ+kTapq5WpySgKVjAfuO6mxcPqPfQe6VRg@mail.gmail.com>
Date: Mon, 15 Jan 2024 03:11:07 +0200
From: Andy Shevchenko <andy.shevchenko@...il.com>
To: Kent Gibson <warthog618@...il.com>
Cc: linux-kernel@...r.kernel.org, linux-gpio@...r.kernel.org, 
	linux-doc@...r.kernel.org, brgl@...ev.pl, linus.walleij@...aro.org, 
	andy@...nel.org, corbet@....net
Subject: Re: [PATCH v2 1/9] Documentation: gpio: add chardev userspace API documentation

On Mon, Jan 15, 2024 at 2:49 AM Kent Gibson <warthog618@...il.com> wrote:
>
> Add documentation for the GPIO character device userspace API.
>
> Added to the userspace-api book, but also provide a link from the
> admin-guide book, as historically the GPIO documentation has been
> there.

..

> +.. note::
> +   Do NOT abuse userspace APIs to control hardware that has proper kernel
> +   drivers. There may already be a driver for your use case, and an existing
> +   kernel driver is sure to provide a superior solution to bitbashing
> +   from userspace.
> +
> +   Read Documentation/driver-api/gpio/drivers-on-gpio.rst to avoid reinventing
> +   kernel wheels in userspace.
> +
> +   Similarly, for multi-function lines there may be other subsystems, such as
> +   Documentation/spi/index.rst, Documentation/i2c/index.rst,
> +   Documentation/driver-api/pwm.rst, Documentation/w1/index.rst etc, that
> +   provide suitable drivers and APIs for your hardware.

Very good note and would be nice to convince users to follow it:
https://stackoverflow.com/q/77683532/2511795
(OOH you might be proud it's Rust, OTOH as described above)

-- 
With Best Regards,
Andy Shevchenko