Re: Generating libbpf API documentation

[Grant Seltzer Richman <grantseltzer@gmail.com>]

On Mon, Mar 15, 2021 at 8:47 PM Andrii Nakryiko
<andrii.nakryiko@gmail.com> wrote:
>
> On Mon, Mar 15, 2021 at 9:51 AM Grant Seltzer Richman
> <grantseltzer@gmail.com> wrote:
> >
> > Hi all,
> >
> > I have been experimenting with ways to contribute documentation to
> > libbpf to make it easier for developers of bpf projects to use it.
> > With the goal of making a documentation site that is easy to
> > maintain/generate I found Doxygen (many of you may have experience
> > with it, I did not). I set up a CI/CD workflow using github actions
> > that runs doxygen on the libbpf mirror hosted there, and hosts the
> > produced HTML using netlify. You can find the currently hosted version
> > of it at https://libbpf-docs.netlify.app (I would gladly donate a real
> > domain name for this purpose). The docs generation workflow is in my
> > github repo here: https://github.com/grantseltzer/libbpf-docs
>
> Thanks for investigating this! I've look at libbpf-docs.netlify.app,
> and it seems like it just contains a list of structs and their fields
> (both those that are part of libbpf API, as well as internal). Out of
> all functions only two are listed there (libbpf_nla_parse_nested and
> libbpf_nla_parse) and both are not part of libbpf API as well. So I
> understand that I don't see any comments due to the '/**' format
> (though it would be easy to run sed script adding it everywhere, just
> as part of an experiment), but I'm not sure why none of API functions
> are present there?
>
> I think kernel docs used to be hosted on readthedocs.org, seems like
> they are also providing hosting for open-source projects, so that
> would solve the problem of the hosting. Have you looked at that
> solution? It definitely has a bit more modern UI that
> Doxygen-generated one :) but I don't know what are the real
> differences between Sphinx and Doxygen and which one we should choose.
>
> >
> > In order to make this work all we would need is to format comments
> > above functions we want to document. Doxygen requires that the comment
> > just be in a block that starts with `/**`. I don't think doxygen
> > specific directives should be committed to code but I think this is a
> > fine convention to follow. Other doxygen directives (i.e. having
> > `@file` in every file) can be faked using a step I have in the github
> > actions.
> >
> > What does everyone think? Can we agree on this convention and start
> > contributing documentation in this way? Any pitfalls to doxygen I'm
> > not familiar with?
> >
> > Thanks!

As far as I understand Doxygen's only criteria for generating
documentation for functions is if the correctly formatted comment is
present. I've changed the repo that the libbpf-docs.netlify.app
website uses to track a fork libbpf I have on my personal account. I
added comments above some ringbuffer functions to demonstrate this.

Interestingly the two functions that already show up
(libbpf_nla_parse/parse_nested) have comments which are specifically
formatted for doxygen, even including directives for arguments and
related functions.

I have heard of Sphinx/read-the-docs but didn't look too deeply into
it, I'll check it out and report back with my findings!