docs: drop the version constraints for sphinx and dependencies

As discussed (see Links), there is some inertia to move to the recent
Sphinx versions for the doc build environment.

As first step, drop the version constraints and the related comments. As
sphinx depends on jinja2, jinja2 is pulled in automatically. So drop that.
Then, the sphinx-pre-install script will fail though with:

Can't get default sphinx version from ./Documentation/sphinx/requirements.txt at ./scripts/sphinx-pre-install line 305.

The script simply expects to parse a version constraint with Sphinx in the
requirements.txt. That version is used in the script for suggesting the
virtualenv directory name.

To suggest a virtualenv directory name, when there is no version given in
the requirements.txt, one could try to guess the version that would be
downloaded with 'pip install -r Documentation/sphinx/requirements.txt'.
However, there seems no simple way to get that version without actually
setting up the venv and running pip. So, instead, name the directory with
the fixed name 'sphinx_latest'.

Finally update the Sphinx build documentation to reflect this directory
name change.

Link: https://lore.kernel.org/linux-doc/874jf4m384.fsf@meer.lwn.net/
Link: https://lore.kernel.org/linux-doc/20240226093854.47830-1-lukas.bulwahn@gmail.com/
Reviewed-by: Akira Yokosawa <akiyks@gmail.com>
Tested-by: Vegard Nossum <vegard.nossum@oracle.com>
Signed-off-by: Lukas Bulwahn <lukas.bulwahn@gmail.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Message-ID: <20240301141800.30218-1-lukas.bulwahn@gmail.com>

Documentation: multiple .rst files: Fix grammar and more consistent formatting

sphinx.rst:
- Remove unnecessary newline
- Fix grammar s/on/in/
- Fix grammar s/check/checks/
- Capitalize heading "The C domain"

changes.rst:
- Remove colon after "pahole" to be consistent with other entries

howto.rst:
- Fix grammar s/you will/will you/
- Hyphenate "real-world problems"

Signed-off-by: Thorsten Blum <thorsten.blum@toblux.com>
Reviewed-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Link: https://lore.kernel.org/r/20240205000117.3285-1-thorsten.blum@toblux.com

docs: Raise the minimum Sphinx requirement to 2.4.4

Commit 31abfdda6527 (docs: Deprecate use of Sphinx < 2.4.x) in 6.2 added a
warning that support for older versions of Sphinx would be going away.
There have been no complaints, so the time has come. Raise the minimum
Sphinx version to 2.4.4 and clean out some compatibility code that we no
longer need.

Reviewed-by: Mauro Carvalho Chehab <mchehab@kernel.org>
Link: https://lore.kernel.org/r/874jgs47fq.fsf@meer.lwn.net
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

docs: automarkup: linkify git revs

There aren't a ton of references to commits in the documentation, but
they do exist, and we can use automarkup to linkify them to make them
easier to follow.

Use something like this to find references to commits:

git grep -P 'commit.*[0-9a-f]{8,}' Documentation/

Also fix a few of these to standardize on the exact format that is
already used in changelogs.

Signed-off-by: Vegard Nossum <vegard.nossum@oracle.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Link: https://lore.kernel.org/r/20231027115420.205279-1-vegard.nossum@oracle.com

docs/doc-guide: Clarify how to write tables

Prior to this commit, the kernel docs writing guide spent over a page
describing exactly how *not* to write tables into the kernel docs,
without providing a example about the desired format.

This patch provides a positive example first in the guide so that it's
harder to miss, then leaves the existing less desirable approach below
for contributors to follow if they have some stronger justification for
why to use that approach.

Signed-off-by: Joe Stringer <joe@isovalent.com>
Reviewed-by: Randy Dunlap <rdunlap@infradead.org>
Link: https://lore.kernel.org/r/20230424171850.3612317-1-joe@isovalent.com
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

docs: update sphinx.rst to reflect the default theme change

We don't default to Read The Docs anymore; update the docs to match.

Acked-by: Mauro Carvalho Chehab <mchehab@kernel.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

docs/doc-guide: Add documentation on SPHINX_IMGMATH

Now that building html docs with math expressions does not need texlive
packages, remove the note on the requirement in the "Sphinx Install"
section.

Instead, add sections of "Math Expressions in HTML" and "Choice of Math
Renderer".
Describe the effect of setting SPHINX_IMGMATH in the latter section.

Signed-off-by: Akira Yokosawa <akiyks@gmail.com>
Cc: Mauro Carvalho Chehab <mchehab@kernel.org>
Cc: Randy Dunlap <rdunlap@infradead.org>
Link: https://lore.kernel.org/r/a67e3279-6bc7-ee2c-2b49-9275252460b0@gmail.com
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

docs/doc-guide: Mention make variable SPHINXDIRS

SPHINXDIRS is useful when you want to test build only those
documents affected by your changes.

Mention it in the "Sphinx Build" section.

Signed-off-by: Akira Yokosawa <akiyks@gmail.com>
Cc: Maciej W. Rozycki <macro@orcam.me.uk>
Link: https://lore.kernel.org/r/50d6f0bc-030d-9529-0665-e2b3e7c792d8@gmail.com
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

docs/doc-guide: Add footnote on Inkscape for better images in PDF documents

With kernel releases v5.18 and later, if you have Inkscape, images
embedded in PDF documents are of vector graphics, not the raster
images as are the case with pre-v5.18 releases.
Even with pre-5.18 releases, having Inkscape would improve images
converted from some of SVG files which are not fully covered by the
limited capability of rsvg-convert(1) [1].

Add a footnote mentioning the expected improvements of such images.

Link: https://gitlab.gnome.org/GNOME/librsvg#non-goals-of-librsvg [1]
Signed-off-by: Akira Yokosawa <akiyks@gmail.com>
Link: https://lore.kernel.org/r/81cddbde-bc28-bec1-fca4-3c8fe2df502f@gmail.com
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

Documentation: sphinx: replace "Introduction" chapter heading with page title

Replace first chapter heading ("Introduction") with page title named
"Using Sphinx for kernel documentation". This way, the first-level TOC
for doc-guide contains title instead of chapter headings for this page.

Cc: Jonathan Corbet <corbet@lwn.net>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Tony Nguyen <anthony.l.nguyen@intel.com>
Cc: Vinod Koul <vkoul@kernel.org>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Cc: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Cc: Akira Yokosawa <akiyks@gmail.com>
Cc: "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: linux-kernel@vger.kernel.org
Reviewed-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Signed-off-by: Bagas Sanjaya <bagasdotme@gmail.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

docs: discourage use of list tables

Our documentation encourages the use of list-table formats, but that advice
runs counter to the objective of keeping the plain-text documentation as
useful and readable as possible. Turn that advice around the other way so
that people don't keep adding these tables.

Acked-by: Christoph Hellwig <hch@lst.de>
Acked-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

docs: address some text issues with css/theme support

Fix:
- overriden ->overridden
- some whitespace issues introduced at the css/theme
Makefile help.

Reported-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Reviewed-by: Randy Dunlap <rdunlap@infradead.org>
Link: https://lore.kernel.org/r/b0b166025019f7cc4f122bd789c79ba28cc2d29d.1639212812.git.mchehab+huawei@kernel.org
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

docs: allow to pass extra DOCS_CSS themes via make

Specially when the RTD theme is not used, it makes sense to
allow specifying extra CSS files via a make variable.

Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Link: https://lore.kernel.org/r/03d09bf41ad39aa0abfe2ea3c879b09aa3a0948d.1638870323.git.mchehab+huawei@kernel.org
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

docs: allow selecting a Sphinx theme

Instead of having RTD as an almost mandatory theme, allow the
user to select other themes via DOCS_THEME environment var.

There's a catch, though: as the current theme override logic is
dependent of the RTD theme, we need to move the code which
adds the CSS overrides to be inside the RTD theme logic.

Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Link: https://lore.kernel.org/r/bd20adabfd428fd3cd0e69c2cf146aa354932936.1638870323.git.mchehab+huawei@kernel.org
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

docs: Update Sphinx requirements

Commit f546ff0c0c07 ("Move our minimum Sphinx version to 1.7") raised
the minimum version to 1.7.

For pdfdocs, sphinx_pre_install says:

note: If you want pdf, you need at least Sphinx 2.4.4.

, and current requirements.txt installs Sphinx 2.4.4.

Update Sphinx versions mentioned in docs and remove a note on earlier
Sphinx versions.

Update zh_CN and it_IT translations as well.

Signed-off-by: Akira Yokosawa <akiyks@gmail.com>
Cc: Federico Vaga <federico.vaga@vaga.pv.it>
Cc: Alex Shi <alexs@kernel.org>
Reviewed-by: Alex Shi <alexs@kernel.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

docs: Document cross-referencing using relative path

Update the Cross-referencing section to explain how to create a
cross-reference to a document using relative paths and with no
additional syntax, by relying on automarkup.py.

Signed-off-by: Nícolas F. R. A. Prado <nfraprado@protonmail.com>
Link: https://lore.kernel.org/r/20210128010028.58541-3-nfraprado@protonmail.com
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

Documentation: doc-guide: fixes to sphinx.rst

Various fixes to sphinx.rst:

- eliminate a double-space between 2 words
- grammar/wording
- punctuation
- call rows in a table 'rows' instead of 'columns' (or does Sphinx
call everything a column?)
- It seems that "amdfonts" should be "amsfonts". I can't find any
amdfonts.

Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Reviewed-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Link: https://lore.kernel.org/r/20201228231212.22448-1-rdunlap@infradead.org
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

Documentation: fix typos found in process, dev-tools, and doc-guide subdirectories

Fix four typos in kcov.rst, sphinx.rst, clang-format.rst, and embargoed-hardware-issues.rst

Signed-off-by: Andrew Klychkov <andrew.a.klychkov@gmail.com>
Acked-by: Randy Dunlap <rdunlap@infradead.org>
Acked-by: Miguel Ojeda <ojeda@kernel.org>
Link: https://lore.kernel.org/r/20201202075438.GA35516@spblnx124.lan
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

docs: Document cross-referencing between documentation pages

The syntax to cross-reference between documentation pages wasn't
documented anywhere.

Document the cross-referencing using the new automarkup for
Documentation/... and also Sphinx's doc directive for using relative
paths.

Signed-off-by: Nícolas F. R. A. Prado <nfraprado@protonmail.com>
Link: https://lore.kernel.org/r/20200911133339.327721-4-nfraprado@protonmail.com
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

docs: Note that :c:func: should no longer be used

Now that we can mark up function() automatically, there is no reason to use
:c:func: and every reason to avoid it. Adjust the documentation to reflect
that fact.

Signed-off-by: Jonathan Corbet <corbet@lwn.net>

sphinx.rst: Add note about code snippets embedded in the text

There's a paragraph that explains how to create fixed width text block,
but it doesn't explains how to create fixed width text inline, although
this feature is really used through the documentation. Fix that adding a
quick note about it.

Signed-off-by: André Almeida <andrealmeid@collabora.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

docs: requirements.txt: recommend Sphinx 1.7.9

As discussed at the linux-doc ML, while we'll still support
version 1.3, it is time to recommend a more modern version.

So, let's switch the minimal requirements to Sphinx 1.7.9,
as it has the "-jauto" flag, with makes a lot faster when
building documentation.

Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

docs-rst: doc-guide: Minor grammar fixes

While using this guide to learn the new documentation method, I saw
a few phrases that I felt could be improved. These small changes
improve the grammar and choice of words to further enhance the
installation instructions.

Signed-off-by: Joel Nider <joeln@il.ibm.com>
Acked-by: Mike Rapoport <rppt@linux.ibm.com>
Acked-by: Matthew Wilcox <willy@infradead.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

doc:process: add links where missing

Some documents are refering to others without links. With this
patch I add those missing links.

This patch affects only documents under process/ and labels where
necessary.

Signed-off-by: Federico Vaga <federico.vaga@vaga.pv.it>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

doc:doc-guide: fix a typo and an error

Fix a typo in sphinx.rst and a minor error in parse-header.rst

Signed-off-by: Federico Vaga <federico.vaga@vaga.pv.it>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

sphinx.rst: Allow Sphinx version 1.6 at the docs

Now that the PDF building issues with Sphinx 1.6 got fixed,
update the documentation and scripts accordingly.

Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

sphinx.rst: document scripts/sphinx-pre-install script

Now that we have a script to check for Sphinx dependencies,
document it.

Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

sphinx.rst: better organize the documentation about PDF build

Instead of having it on just one note, add a separate section.

This way, we could later improve it, providing a better
guide about the needed steps for PDF builds.

Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

sphinx.rst: describe the install requirements for kfigure

As we now have a document describing the install
requirements for Sphinx, add there the need for GraphViz
and ImageMagick.

Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

sphinx.rst: fix unknown reference

There's no "Sphinx C Domain" reference at the Kernel
documentation. So, don't use references for it.

Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

sphinx.rst: explain the usage of virtual environment

As the Sphinx build seems very fragile, specially for
PDF output, add a notice about how to use it on a virtual
environment.

Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

docs-rst: move Sphinx install instructions to sphinx.rst

The toolchain used by Sphinx is somewhat complex, and installing
it should be part of the doc-guide.

Move it out of changes.rst.

Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

docs: update old references for DocBook from the documentation

DocBook is mentioned several times at the documentation. Update
the obsolete references from it at the DocBook.

Acked-by: SeongJae Park <sj38.park@gmail.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>

docs-rst: automatically convert Graphviz and SVG images

This patch brings scalable figure, image handling and a concept to
embed *render* markups:

* DOT (http://www.graphviz.org)
* SVG

For image handling use the 'image' replacement::

.. kernel-image:: svg_image.svg
:alt: simple SVG image

For figure handling use the 'figure' replacement::

.. kernel-figure:: svg_image.svg
:alt: simple SVG image

SVG image example

Embed *render* markups (or languages) like Graphviz's **DOT** is
provided by the *render* directive.::

.. kernel-render:: DOT
:alt: foobar digraph
:caption: Embedded **DOT** (Graphviz) code.

digraph foo {
"bar" -> "baz";
}

The *render* directive is a concept to integrate *render* markups and
languages, yet supported markups:

* DOT: render embedded Graphviz's **DOT**
* SVG: render embedded Scalable Vector Graphics (**SVG**)

Cc: Jani Nikula <jani.nikula@linux.intel.com>
Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Tested-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>
Tested-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com> (v2 - v5)
Signed-off-by: Markus Heiser <markus.heiser@darmarit.de> (v1, v6)
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

doc: Explain light-handed markup preference a bit better

We're still pretty far away from anything like a consensus, but
there's clearly a lot of people who prefer an as-light as possible
approach to converting existing .txt files to .rst. Make sure this is
properly taken into account and clear.

Motivated by discussions with Peter and Christoph and others.

Cc: Christoph Hellwig <hch@infradead.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Jani Nikula <jani.nikula@linux.intel.com>
Cc: Mauro Carvalho Chehab <mchehab@s-opensource.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

docs-rst: doc-guide: split the kernel-documentation.rst contents

Having the kernel-documentation at the topmost level doesn't
allow generating a separate PDF file for it. Also, makes harder
to add extra contents. So, place it on a sub-dir.

Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>