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-rw-r--r--Documentation/doc-guide/sphinx.rst57
1 files changed, 53 insertions, 4 deletions
diff --git a/Documentation/doc-guide/sphinx.rst b/Documentation/doc-guide/sphinx.rst
index 1228b85f6f77..c708cec889af 100644
--- a/Documentation/doc-guide/sphinx.rst
+++ b/Documentation/doc-guide/sphinx.rst
@@ -48,10 +48,6 @@ or ``virtualenv``, depending on how your distribution packaged Python 3.
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 Sphinx version 2.4.4, you should do::
$ virtualenv sphinx_2.4.4
@@ -86,6 +82,27 @@ 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
@@ -164,6 +181,38 @@ To remove the generated documentation, run ``make cleandocs``.
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
=====================