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Diffstat (limited to 'Documentation/doc-guide/sphinx.rst')
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1 files changed, 145 insertions, 42 deletions
diff --git a/Documentation/doc-guide/sphinx.rst b/Documentation/doc-guide/sphinx.rst index ec3e71f56009..51c370260f3b 100644 --- a/Documentation/doc-guide/sphinx.rst +++ b/Documentation/doc-guide/sphinx.rst @@ -1,7 +1,8 @@ .. _sphinxdoc: -Introduction -============ +===================================== +Using Sphinx for kernel documentation +===================================== The Linux kernel uses `Sphinx`_ to generate pretty documentation from `reStructuredText`_ files under ``Documentation``. To build the documentation in @@ -27,7 +28,7 @@ Sphinx Install ============== The ReST markups currently used by the Documentation/ files are meant to be -built with ``Sphinx`` version 1.3 or higher. +built with ``Sphinx`` version 3.4.3 or higher. There's a script that checks for the Sphinx requirements. Please see :ref:`sphinx-pre-install` for further details. @@ -41,27 +42,14 @@ with your distributions. In order to do so, it is recommended to install Sphinx inside a virtual environment, using ``virtualenv-3`` or ``virtualenv``, depending on how your distribution packaged Python 3. -.. note:: - - #) Sphinx versions below 1.5 don't work properly with Python's - docutils version 0.13.1 or higher. So, if you're willing to use - those versions, you should run ``pip install 'docutils==0.12'``. - - #) It is recommended to use the RTD theme for html output. Depending - on the Sphinx version, it should be installed separately, - with ``pip install sphinx_rtd_theme``. - - #) Some ReST pages contain math expressions. Due to the way Sphinx works, - those expressions are written using LaTeX notation. It needs texlive - installed with amsfonts and amsmath in order to evaluate them. +In summary, if you want to install the latest version of Sphinx, you +should do:: -In summary, if you want to install Sphinx version 1.7.9, you should do:: + $ virtualenv sphinx_latest + $ . sphinx_latest/bin/activate + (sphinx_latest) $ pip install -r Documentation/sphinx/requirements.txt - $ virtualenv sphinx_1.7.9 - $ . sphinx_1.7.9/bin/activate - (sphinx_1.7.9) $ pip install -r Documentation/sphinx/requirements.txt - -After running ``. sphinx_1.7.9/bin/activate``, the prompt will change, +After running ``. sphinx_latest/bin/activate``, the prompt will change, in order to indicate that you're using the new environment. If you open a new shell, you need to rerun this command to enter again at the virtual environment before building the documentation. @@ -70,8 +58,7 @@ Image output ------------ The kernel documentation build system contains an extension that -handles images on both GraphViz and SVG formats (see -:ref:`sphinx_kfigure`). +handles images in both GraphViz and SVG formats (see :ref:`sphinx_kfigure`). For it to work, you need to install both GraphViz and ImageMagick packages. If those packages are not installed, the build system will @@ -81,7 +68,7 @@ output. PDF and LaTeX builds -------------------- -Such builds are currently supported only with Sphinx versions 1.4 and higher. +Such builds are currently supported only with Sphinx versions 2.4 and higher. For PDF and LaTeX output, you'll also need ``XeLaTeX`` version 3.14159265. @@ -89,26 +76,47 @@ Depending on the distribution, you may also need to install a series of ``texlive`` packages that provide the minimal set of functionalities required for ``XeLaTeX`` to work. +Math Expressions in HTML +------------------------ + +Some ReST pages contain math expressions. Due to the way Sphinx works, +those expressions are written using LaTeX notation. +There are two options for Sphinx to render math expressions in html output. +One is an extension called `imgmath`_ which converts math expressions into +images and embeds them in html pages. +The other is an extension called `mathjax`_ which delegates math rendering +to JavaScript capable web browsers. +The former was the only option for pre-6.1 kernel documentation and it +requires quite a few texlive packages including amsfonts and amsmath among +others. + +Since kernel release 6.1, html pages with math expressions can be built +without installing any texlive packages. See `Choice of Math Renderer`_ for +further info. + +.. _imgmath: https://www.sphinx-doc.org/en/master/usage/extensions/math.html#module-sphinx.ext.imgmath +.. _mathjax: https://www.sphinx-doc.org/en/master/usage/extensions/math.html#module-sphinx.ext.mathjax + .. _sphinx-pre-install: Checking for Sphinx dependencies -------------------------------- -There's a script that automatically check for Sphinx dependencies. If it can +There's a script that automatically checks for Sphinx dependencies. If it can recognize your distribution, it will also give a hint about the install command line options for your distro:: - $ ./scripts/sphinx-pre-install + $ ./tools/docs/sphinx-pre-install Checking if the needed tools for Fedora release 26 (Twenty Six) are available Warning: better to also install "texlive-luatex85". You should run: sudo dnf install -y texlive-luatex85 - /usr/bin/virtualenv sphinx_1.7.9 - . sphinx_1.7.9/bin/activate + /usr/bin/virtualenv sphinx_2.4.4 + . sphinx_2.4.4/bin/activate pip install -r Documentation/sphinx/requirements.txt - Can't build as 1 mandatory dependency is missing at ./scripts/sphinx-pre-install line 468. + Can't build as 1 mandatory dependency is missing at ./tools/docs/sphinx-pre-install line 468. By default, it checks all the requirements for both html and PDF, including the requirements for images, math expressions and LaTeX build, and assumes @@ -123,6 +131,29 @@ It supports two optional parameters: ``--no-virtualenv`` Use OS packaging for Sphinx instead of Python virtual environment. +Installing Sphinx Minimal Version +--------------------------------- + +When changing Sphinx build system, it is important to ensure that +the minimal version will still be supported. Nowadays, it is +becoming harder to do that on modern distributions, as it is not +possible to install with Python 3.13 and above. + +Testing with the lowest supported Python version as defined at +Documentation/process/changes.rst can be done by creating +a venv with it with, and install minimal requirements with:: + + /usr/bin/python3.9 -m venv sphinx_min + . sphinx_min/bin/activate + pip install -r Documentation/sphinx/min_requirements.txt + +A more comprehensive test can be done by using: + + tools/docs/test_doc_build.py + +Such script create one Python venv per supported version, +optionally building documentation for a range of Sphinx versions. + Sphinx Build ============ @@ -133,17 +164,72 @@ section of ``make help``. The generated documentation is placed in format-specific subdirectories under ``Documentation/output``. To generate documentation, Sphinx (``sphinx-build``) must obviously be -installed. For prettier HTML output, the Read the Docs Sphinx theme -(``sphinx_rtd_theme``) is used if available. For PDF output you'll also need -``XeLaTeX`` and ``convert(1)`` from ImageMagick (https://www.imagemagick.org). -All of these are widely available and packaged in distributions. +installed. For PDF output you'll also need ``XeLaTeX`` and ``convert(1)`` +from ImageMagick (https://www.imagemagick.org).\ [#ink]_ All of these are +widely available and packaged in distributions. To pass extra options to Sphinx, you can use the ``SPHINXOPTS`` make variable. For example, use ``make SPHINXOPTS=-v htmldocs`` to get more verbose output. +It is also possible to pass an extra DOCS_CSS overlay file, in order to customize +the html layout, by using the ``DOCS_CSS`` make variable. + +By default, the "Alabaster" theme is used to build the HTML documentation; +this theme is bundled with Sphinx and need not be installed separately. +The Sphinx theme can be overridden by using the ``DOCS_THEME`` make variable. + +.. note:: + + Some people might prefer to use the RTD theme for html output. + Depending on the Sphinx version, it should be installed separately, + with ``pip install sphinx_rtd_theme``. + +There is another make variable ``SPHINXDIRS``, which is useful when test +building a subset of documentation. For example, you can build documents +under ``Documentation/doc-guide`` by running +``make SPHINXDIRS=doc-guide htmldocs``. +The documentation section of ``make help`` will show you the list of +subdirectories you can specify. + To remove the generated documentation, run ``make cleandocs``. +.. [#ink] Having ``inkscape(1)`` from Inkscape (https://inkscape.org) + as well would improve the quality of images embedded in PDF + documents, especially for kernel releases 5.18 and later. + +Choice of Math Renderer +----------------------- + +Since kernel release 6.1, mathjax works as a fallback math renderer for +html output.\ [#sph1_8]_ + +Math renderer is chosen depending on available commands as shown below: + +.. table:: Math Renderer Choices for HTML + + ============= ================= ============ + Math renderer Required commands Image format + ============= ================= ============ + imgmath latex, dvipng PNG (raster) + mathjax + ============= ================= ============ + +The choice can be overridden by setting an environment variable +``SPHINX_IMGMATH`` as shown below: + +.. table:: Effect of Setting ``SPHINX_IMGMATH`` + + ====================== ======== + Setting Renderer + ====================== ======== + ``SPHINX_IMGMATH=yes`` imgmath + ``SPHINX_IMGMATH=no`` mathjax + ====================== ======== + +.. [#sph1_8] Fallback of math renderer requires Sphinx >=1.8. + + Writing Documentation ===================== @@ -220,7 +306,7 @@ Here are some specific guidelines for the kernel documentation: from highlighting. For a short snippet of code embedded in the text, use \`\`. -the C domain +The C domain ------------ The **Sphinx C Domain** (name c) is suited for documentation of C API. E.g. a @@ -250,16 +336,24 @@ the documentation build system will automatically turn a reference to function name exists. If you see ``c:func:`` use in a kernel document, please feel free to remove it. +Tables +------ + +ReStructuredText provides several options for table syntax. Kernel style for +tables is to prefer *simple table* syntax or *grid table* syntax. See the +`reStructuredText user reference for table syntax`_ for more details. + +.. _reStructuredText user reference for table syntax: + https://docutils.sourceforge.io/docs/user/rst/quickref.html#tables list tables ------------ +~~~~~~~~~~~ -We recommend the use of *list table* formats. The *list table* formats are -double-stage lists. Compared to the ASCII-art they might not be as -comfortable for -readers of the text files. Their advantage is that they are easy to -create or modify and that the diff of a modification is much more meaningful, -because it is limited to the modified content. +The list-table formats can be useful for tables that are not easily laid +out in the usual Sphinx ASCII-art formats. These formats are nearly +impossible for readers of the plain-text documents to understand, though, +and should be avoided in the absence of a strong justification for their +use. The ``flat-table`` is a double-stage list similar to the ``list-table`` with some additional features: @@ -364,6 +458,15 @@ path. For information on cross-referencing to kernel-doc functions or types, see Documentation/doc-guide/kernel-doc.rst. +Referencing commits +~~~~~~~~~~~~~~~~~~~ + +References to git commits are automatically hyperlinked given that they are +written in one of these formats:: + + commit 72bf4f1767f0 + commit 72bf4f1767f0 ("net: do not leave an empty skb in write queue") + .. _sphinx_kfigure: Figures & Images |