Re: [libgpiod] Documentation question

[Kent Gibson <warthog618@xxxxxxxxx>]

On Sat, Dec 30, 2023 at 08:04:40PM -0600, Seamus de Mora wrote:
> Hello,
>
> I read a description of libgpiod recently that I cannot find... (my
> well-organized reference catalogs have failed me  :) I'm hoping
> someone here can help me.
>
> The documentation I read made a point about libgpiod restricting
> itself to GPIO; i.e. not I2C, SPI, PWM and a host of other specialized
> GPIO interfaces.
>

It is kind of in the name ;-).

The headline of the README is

  libgpiod - C library and tools for interacting with the linux GPIO
             character device (gpiod stands for GPIO device)

It doesn't describe what it doesn't do, only what it does.
And the scope of the GPIO character device uAPI is to expose the
functionality of the GPIO subsystem to user-space.

> I thought it was in the libgpiod README, but it's not. Any ideas on
> where I might find this?
>

Like you, I can't even find the brief documentation on the GPIO uAPI
that I thought was in the Linux kernel documentation - the only thing I
can find is a reference to gpio.h itself, which is not very helpful.
Something else to add to the todo list.

The closest thing I can find to what I think you are after is the pinctrl
documentation[1], particularly the "GPIO mode pitfalls" section[2] - but
the whole thing is worth a read.

Cheers,
Kent.

[1] https://docs.kernel.org/driver-api/pin-control.html
[2] https://docs.kernel.org/driver-api/pin-control.html#gpio-mode-pitfalls