Re: [libgpiod] Documentation question

[Seamus de Mora <seamusdemora@xxxxxxxxx>]

> On Sat, Dec 30, 2023 at 9:51 PM Kent Gibson <warthog618@xxxxxxxxx> wrote:
> >
> > 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

The pinctrl refs didn't have what I was looking for, but thanks & keep
your eyes peeled, please. I found something close (and a surprise) in
this item named 'Using GPIO Lines in Linux'[1]. The surprise was the
recommendation against using the ABI (libgpiod??) for "production
systems". Am I reading that correctly?

[1] https://www.kernel.org/doc/html/latest/driver-api/gpio/using-gpio.html