linux-kernel - Re: [PATCH 0/7] Documentation: gpio: add character device userspace API documentation

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Date: Fri, 12 Jan 2024 09:03:07 +0800
From: Kent Gibson <warthog618@...il.com>
To: Andy Shevchenko <andy.shevchenko@...il.com>
Cc: Vegard Nossum <vegard.nossum@...cle.com>, 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 0/7] Documentation: gpio: add character device userspace
 API documentation

On Wed, Jan 10, 2024 at 01:10:51PM +0200, Andy Shevchenko wrote:
> On Wed, Jan 10, 2024 at 10:16 AM Vegard Nossum <vegard.nossum@...cle.com> wrote:
> > On 10/01/2024 00:45, Kent Gibson wrote:
> > > On Tue, Jan 09, 2024 at 10:00:26PM +0200, Andy Shevchenko wrote:
> > >> On Tue, Jan 9, 2024 at 4:00 PM Kent Gibson <warthog618@...il.com> wrote:
> > >>
> > >> May we actually state in the documentation that sysfs is subject to
> > >> remove at some point?
> > >
> > > So formally define what "deprecated" means?
> > > Is that covered in the higher level documentation somewhere?
> > > If so I'm more than happy to provide a reference.
> >
> > We have a few files that may be relevant here, that I'm aware of:
> >
> > 1) https://docs.kernel.org/admin-guide/sysfs-rules.html
> >
> > documents some general assumptions that userspace can make about the
> > stability of sysfs and its files
> >
> > 2) https://docs.kernel.org/admin-guide/abi.html
> >
> > This is the public-facing, somewhat machine-readable repository of what
> > is supposed to be the kernel's ABI/API, including "obsolete" and
> > "removed" interfaces.
> >
> > 3) Documentation/ABI/README
> >
> > describes the process of deprecating an interface
>
> Yes and GPIO currently is under obsolete section with also this:
>
> "This ABI is deprecated and will be removed after 2020. It is replaced
> with the GPIO character device."
>
> https://docs.kernel.org/admin-guide/abi-obsolete.html#symbols-under-sys-class
>
> So, proposed cleanup series should probably rely on this documentation
> among other existing descriptions of sysfs GPIO.
>

The sysfs doc already references the doc (sysfs-gpio) that generates the
HTML that link points to, so not sure what to change.
I can't include a direct reference to the HTML, AFAICT, as that HTML is
generated using kernel-abi makefile magic so the usual doc path
cross-references don't work - you just get the path as plain text.

If there is some way to provide a cross-reference that generates to that
link then I'll change it, but I don't know how.

>>> +    -  -  ``EFAULT``

> Wondering if these constants can be referenced via % and if it makes sense.

That would be great and I do want to do that, particularly for the
uAPI v1 docs that use a lot of consts rather than enums, but, AFAICT, you
can't create cross-references for consts, you can only add formatting[1].
And the % formatting only works in kernel-doc, in rst you have to add it
explicitly yourself, hence the ``EFAULT`` .

Cheers,
Kent.
[1] https://www.kernel.org/doc/html/latest/doc-guide/kernel-doc.html#highlights-and-cross-references