Message-Id: <8992F589-5B66-4BDB-807A-79AC8644F006@darmarit.de>
Date:	Fri, 8 Apr 2016 17:12:27 +0200
From:	Markus Heiser <markus.heiser@...marit.de>
To:	Mauro Carvalho Chehab <mchehab@....samsung.com>,
	Jani Nikula <jani.nikula@...el.com>,
	Dan Allen <dan@...ndevise.io>,
	Russel Winder <russel@...der.org.uk>,
	Keith Packard <keithp@...thp.com>,
	Jonathan Corbet <corbet@....net>,
	LKML <linux-kernel@...r.kernel.org>,
	"linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
	Daniel Vetter <daniel.vetter@...ll.ch>,
	Hans Verkuil <hverkuil@...all.nl>,
	"linux-media@...r.kernel.org linux-media" 
	<linux-media@...r.kernel.org>,
	Graham Whaley <graham.whaley@...ux.intel.com>
Subject: Re: Kernel docs: muddying the waters a bit

Hi kernel-doc authors,

motivated by this MT, I implemented a toolchain to migrate the kernel’s 
DocBook XML documentation to reST markup. 

It converts 99% of the docs well ... to gain an impression how 
kernel-docs could benefit from, visit my sphkerneldoc project page
on github:

  http://return42.github.io/sphkerneldoc/

The sources available at:

  https://github.com/return42/sphkerneldoc

The work is underway, suggestions are welcome!

.. have a nice weekend ..

--M--


Am 13.03.2016 um 16:33 schrieb Markus Heiser <markus.heiser@...marIT.de>:

> 
> Am 10.03.2016 um 16:21 schrieb Mauro Carvalho Chehab <mchehab@....samsung.com>:
> 
>> Em Thu, 10 Mar 2016 12:25:58 +0200
>> Jani Nikula <jani.nikula@...el.com> escreveu:
>> 
>>> TL;DR? Skip to the last paragraph.
>>> 
>>> On Wed, 09 Mar 2016, Mauro Carvalho Chehab <mchehab@....samsung.com> wrote:
>>>> I guess the conversion to asciidoc format is now in good shape,
>>>> at least to demonstrate that it is possible to use this format for the
>>>> media docbook. Still, there are lots of broken references.  
>>> 
>>> Getting references right with asciidoc is a big problem in the
>>> kernel-doc side. As I wrote before, the proofs of concept only worked
>>> because everything was processed as one big file (via includes). The
>>> Asciidoctor inter-document references won't help, because we won't know
>>> the target document name while processing kernel-doc.
>> 
>> I was able to produce chunked htmls here with:
>> 
>> 	asciidoctor -b docbook45 media_api.adoc
>> 	xmlto -o html-dir html media_api.xml
>> 
>> The results are at:
>> 	https://mchehab.fedorapeople.org/media-kabi-docs-test/asciidoc_tests/chunked/
>> 
>> But yeah, all references seem to be broken there. It could be due to some
>> conversion issue (I didn't actually tried to check what's wrong there),
>> but I think that there's something not ok with docbook45
>> output for multi-part documents (on both AsciiDoc and Asciidoctor).
>> 
>>> Sphinx is massively better at handling cross references for
>>> kernel-doc. We can use domains (C language) and roles (e.g. functions,
>>> types, etc.) for the references, which provide kind of
>>> namespaces. Sphinx warns for referencing non-existing targets, but
>>> doesn't generate broken links in the result like Asciidoctor does.
>>> 
>>> For example, in the documentation for a function that has struct foo as
>>> parameter or return type, a cross reference to struct foo is added
>>> automagically, but only if documentation for struct foo actually
>>> exists. In Asciidoctor, we would have to blindly generate the references
>>> ourselves, and try to resolve broken links ourselves by somehow
>>> post-processing the result.
>>> 
>>>> Yet, from my side, if we're willing to get rid of DocBook, then
>>>> Asciidoctor seems to be the *only* alternative so far to parse the
>>>> complex media documents.  
>>> 
>>> I think you mean, "get rid of DocBook as source format", not altogether?
>>> I'm yet to be convinved we could rely on Asciidoctor's native formats.
>> 
>> What I mean is that, right now, I see only two alternatives for the
>> media uAPI documentation:
>> 	1) keep using DocBook;
>> 	2) AsciiDoc/Asciidoctor.
>> 
>> Sphinx doesn't have what's needed to support the complexity of the
>> media books, specially since cell span seems to be possible only
>> by using asciiArt formats. Writing a big table using asciiArt is
>> something that is a *real pain*. Also, as tested, if the table is
>> too big, it fails to parse such asciiArt tables. So, while Sphinx
>> doesn't have a decent way to describe tables, we can't use it.
> 
> 
> Huge tables and cell-spans are the *real pain* ;-) ... with sphinx-doc,
> (mostly) you have more then one choice .. e.g. import csv tables .. 
> but this should be discussed by example ...
> 
> 
>> If it starts implementing it, then we can check if the other
>> features used by the media documentation are also supported.
>> Probably, multi-part books would be another pain with Sphinx.
>> We have actually 4 books inside a common body. A few chapters
>> (like book licensing, bibliography, error codes) are shared
>> by all 4 documents.
>> 
>> But, so far, I can't see any way to port media books without
>> lots of lot of work to develop new features at the Sphinx code.
> 
> 
> may I can help you ...
> 
> 
>>> The toolchain gets faster, easier to debug and simplified a lot with
>>> DocBook out of the equation completely. Sphinx itself is stable, widely
>>> available, and well documented. IMO there's sufficient native output
>>> format support. There are plenty of really nice extensions
>>> available. There's a possibility of doing kernel-doc as an extension in
>>> the future (either by calling current kernel-doc from the extension or
>>> by rewriting it).
>> 
>> Well, if we go to Sphinx for kernel-doc, that means that we'll need
>> 2 different tools for the documentation:
>> 	- Sphinx for kernel-doc
>> 	- either DocBook or Asciidoctor/AsciiDoc for media.
>> 
>> IMHO, this is the worse scenario, as we'll keep depending on
>> DocBook plus requiring Sphinx, but it is up to Jon to decide.
>> 
> 
> The migration of kernel-doc is a long term project, not a
> one shot job. The scope of documents to migrate is not limited
> to the files with DocBook markup in, most documents have not
> a real markup.
> 
> Please take a look at my thoughts and efforts about migration.
> 
> * https://sphkerneldoc.readthedocs.org
> 
> * https://github.com/return42/sphkerneldoc.git
> 
> sphkerneldoc.git is a small project started this weekend, within
> this project I show you, how migration could be done and
> we can discuss concerns like "tables and cell-spans" by example. 
> 
> Believe me, most concerns discussed in this thread are a leak of
> knowledge. I'am working with sphinx-doc since 7 years, switched
> over from DocBook (escaped from a 8 years lasting XML hell).
> DocBook and sphinx-doc are complete different, so sphinx-doc
> might feels odd in the first time, but if you have switched 
> like me, you will never go back again.
> 
>>> Dan keeps bringing up the active community in Asciidoctor, and how
>>> they're fixing things up as we speak... which is great, but Sphinx is
>>> here now, packaged and shipping in distros ready to use. It seems that
>>> of the two, an Asciidoctor based toolchain is currently more in need of
>>> hacking and extending to meet our needs. Which brings us to the
>>> implementation language, Python vs. Ruby.
>>> 
>>> I won't make the mistake of comparing the relative merits of the
>>> languages, but I'll boldly claim the set of kernel developers who know
>>> Python is likely larger than the set of kernel developers who know Ruby
>>> [citation needed]. AFAICT there are no Ruby tools in the kernel tree,
>>> but there is a bunch of Python. My own very limited and subjective
>>> experience with other tools around the kernel is that Python is much
>>> more popular than Ruby. So my claim here is that we're in a better
>>> position to hack on Sphinx extensions ourselves than Asciidoctor.
>> 
>> Sorry, but I don't buy it. Python is, IMHO, a mess: each new version
>> is incompatible with the previous one, and requires the source to
>> change, in order to use a newer version than the one used to write
>> the code. So, when talking about Python, we're actually talking about
>> several different dialects that don't talk well to each other.
> 
> Sorry, you are complete wrong ... I'am 15 years python programmer,
> shipped out huge projects with my customers ... we never have seen
> these problems ... sorry ...
> 
> 
>> I don't know about Ruby. So far, I don't have anything against (or in
>> favor) of it. I bet most Kernel developers would actually prefer a
>> toolchain in C. If such tool doesn't exist, anything else seems
>> equally the same ;)
> 
> Why we are talking about script languages? What needed is a 
> authoring system, which is as near as possible to the developers,
> which are the authors.
> 
> Sphinx-Doc is a standard authoring-tool versioned, maintained 
> and extended by thousands of developers ...
> 
> 
>>> My conclusion is that Sphinx covers the vast majority of the needs of
>>> our documentation producers and consumers, in an amazing way, out of the
>>> box, better than Asciidoctor.
>>> 
>>> Which brings us to the minority and the parts where Sphinx falls short,
>>> media documentation in particular. It's complex documentation, with very
>>> specific requirements on the output, especially that many things remain
>>> exactly as they are now. It also feels like the target is more to have
>>> standalone media documentation, and not so much to be aligned with and
>>> be part of the rest of the kernel documentation.
>>> 
>>> I want to question the need to have all kernel documentation use tools
>>> that meet the strict requirements of the outlier, when there's a better
>>> alternative for the vast majority of the documentation. Especially when
>>> Asciidoctor isn't a ready solution for media documentation either.
>>> 
>>> In summary, my proposal is to go with Sphinx, leave media docs as
>>> DocBook for now, and see if and how they can be converted to
>>> Sphinx/reStructuredText later on when we have everything else in
>>> place. It's not the perfect outcome, but IMHO it's the best overall
>>> choice.
>> 
>> Well, this could be done. We don't have any good reason to move
>> the media docs out of DocBook.
> 
> Sorry but again wrong: you lost many of the authors which are 
> frustrated by a XML markup and you lost many developers to improve
> the toolchain, frustrated by a complicated DocBook-XML XSLT
> toolchain with SGML markup from the middle of the last epoch.
> 
>> On the contrary, this means an extra
>> work. The only advantage is that it is a way simpler to write
>> documentation with a markup language, but converting from the PoC
>> to its integration at the Kernel tree still require lots of work,
>> specially due to the cross-refs "magic" scripts that we have under
>> Documentation/DocBook/media/Makefile.
> 
> Yes, you are right, migration is a process not a one shot 
> job, as I mentioned before. You are a great programmer, your 
> documentation is also great, this invest should be preserved.
> So lets take a try. It would be a honor for me to show 
> you all theses steps by example on my repository (see above).
> 
>> As I said, the only big drawback is to keep depending on two
>> different tools for kernel-doc and for media documentation.
> 
> -- Markus --
> 
> 
> --
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