Re: [PATCH bpf-next 00/17] Improve BPF syscall command documentation

Joe Stringer
2021-02-18T21:54:36Z

On Thu, Feb 18, 2021 at 11:49 AM Jonathan Corbet <corbet@lwn.net> wrote:
>
> Joe Stringer <joe@cilium.io> writes:
> > * The changes in patch 16 here extended Documentation/bpf/index.rst,
> > but to assist in improving the overall kernel documentation
> > organisation / hierarchy, you would prefer to instead introduce a
> > dedicated Documentation/userspace-api/bpf/ directory where the bpf
> > uAPI portions can be documented.
>
> An objective I've been working on for some years is reorienting the
> documentation with a focus on who the readers are. We've tended to
> organize it by subsystem, requiring people to wade through a lot of
> stuff that isn't useful to them. So yes, my preference would be to
> document the kernel's user-space API in the relevant manual.
>
> That said, I do tend to get pushback here at times, and the BPF API is
> arguably a bit different that much of the rest. So while the above
> preference exists and is reasonably strong, the higher priority is to
> get good, current documentation in *somewhere* so that it's available to
> users. I don't want to make life too difficult for people working
> toward that goal, even if I would paint it a different color.

Sure, I'm all for it. Unless I hear alternative feedback I'll roll it
under Documentation/userspace-api/bpf in the next revision.

> > In addition to this, today the bpf helpers documentation is built
> > through the bpftool build process as well as the runtime bpf
> > selftests, mostly as a way to ensure that the API documentation
> > conforms to a particular style, which then assists with the generation
> > of ReStructured Text and troff output. I can probably simplify the
> > make infrastructure involved in triggering the bpf docs build for bpf
> > subsystem developers and maintainers. I think there's likely still
> > interest from bpf folks to keep that particular dependency in the
> > selftests like today and even extend it to include this new
> > Documentation, so that we don't either introduce text that fails
> > against the parser or in some other way break the parser. Whether that
> > validation is done by scripts/kernel-doc or scripts/bpf_helpers_doc.py
> > doesn't make a big difference to me, other than I have zero experience
> > with Perl. My first impressions are that the bpf_helpers_doc.py is
> > providing stricter formatting requirements than what "DOC: " +
> > kernel-doc would provide, so my baseline inclination would be to keep
> > those patches to enhance that script and use that for the validation
> > side (help developers with stronger linting feedback), then use
> > kernel-doc for the actual html docs generation side, which would help
> > to satisfy your concern around duplication of the documentation build
> > systems.
>
> This doesn't sound entirely unreasonable. I wonder if the BPF helper
> could be built into an sphinx extension to make it easy to pull that
> information into the docs build. The advantage there is that it can be
> done in Python :)

Probably doable, it's already written in python. One thing at a time
though... :)

Cheers,
Joe