Documentation/doc-guide/sphinx.rst - linux - Git at Google

 Introduction
 ============

 The Linux kernel uses `Sphinx`_ to generate pretty documentation from
 `reStructuredText`_ files under ``Documentation``. To build the documentation in
 HTML or PDF formats, use ``make htmldocs`` or ``make pdfdocs``. The generated
 documentation is placed in ``Documentation/output``.

 .. _Sphinx: http://www.sphinx-doc.org/
 .. _reStructuredText: http://docutils.sourceforge.net/rst.html

 The reStructuredText files may contain directives to include structured
 documentation comments, or kernel-doc comments, from source files. Usually these
 are used to describe the functions and types and design of the code. The
 kernel-doc comments have some special structure and formatting, but beyond that
 they are also treated as reStructuredText.

 There is also the deprecated DocBook toolchain to generate documentation from
 DocBook XML template files under ``Documentation/DocBook``. The DocBook files
 are to be converted to reStructuredText, and the toolchain is slated to be
 removed.

 Finally, there are thousands of plain text documentation files scattered around
 ``Documentation``. Some of these will likely be converted to reStructuredText
 over time, but the bulk of them will remain in plain text.

 Sphinx Build
 ============

 The usual way to generate the documentation is to run ``make htmldocs`` or
 ``make pdfdocs``. There are also other formats available, see the documentation
 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, ``rst2pdf`` is also
 needed. 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.

 To remove the generated documentation, run ``make cleandocs``.

 Writing Documentation
 =====================

 Adding new documentation can be as simple as:

 1. Add a new ``.rst`` file somewhere under ``Documentation``.
 2. Refer to it from the Sphinx main `TOC tree`_ in ``Documentation/index.rst``.

 .. _TOC tree: http://www.sphinx-doc.org/en/stable/markup/toctree.html

 This is usually good enough for simple documentation (like the one you're
 reading right now), but for larger documents it may be advisable to create a
 subdirectory (or use an existing one). For example, the graphics subsystem
 documentation is under ``Documentation/gpu``, split to several ``.rst`` files,
 and has a separate ``index.rst`` (with a ``toctree`` of its own) referenced from
 the main index.

 See the documentation for `Sphinx`_ and `reStructuredText`_ on what you can do
 with them. In particular, the Sphinx `reStructuredText Primer`_ is a good place
 to get started with reStructuredText. There are also some `Sphinx specific
 markup constructs`_.

 .. _reStructuredText Primer: http://www.sphinx-doc.org/en/stable/rest.html
 .. _Sphinx specific markup constructs: http://www.sphinx-doc.org/en/stable/markup/index.html

 Specific guidelines for the kernel documentation
 ------------------------------------------------

 Here are some specific guidelines for the kernel documentation:

 * Please don't go overboard with reStructuredText markup. Keep it simple.

 * Please stick to this order of heading adornments:

   1. ``=`` with overline for document title::

        ==============
        Document title
        ==============

   2. ``=`` for chapters::

        Chapters
        ========

   3. ``-`` for sections::

        Section
        -------

   4. ``~`` for subsections::

        Subsection
        ~~~~~~~~~~

   Although RST doesn't mandate a specific order ("Rather than imposing a fixed
   number and order of section title adornment styles, the order enforced will be
   the order as encountered."), having the higher levels the same overall makes
   it easier to follow the documents.


 the C domain
 ------------

 The `Sphinx C Domain`_ (name c) is suited for documentation of C API. E.g. a
 function prototype:

 .. code-block:: rst

     .. c:function:: int ioctl( int fd, int request )

 The C domain of the kernel-doc has some additional features. E.g. you can
 *rename* the reference name of a function with a common name like ``open`` or
 ``ioctl``:

 .. code-block:: rst

      .. c:function:: int ioctl( int fd, int request )
         :name: VIDIOC_LOG_STATUS

 The func-name (e.g. ioctl) remains in the output but the ref-name changed from
 ``ioctl`` to ``VIDIOC_LOG_STATUS``. The index entry for this function is also
 changed to ``VIDIOC_LOG_STATUS`` and the function can now referenced by:

 .. code-block:: rst

      :c:func:`VIDIOC_LOG_STATUS`


 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 ``flat-table`` is a double-stage list similar to the ``list-table`` with
 some additional features:

 * column-span: with the role ``cspan`` a cell can be extended through
   additional columns

 * row-span: with the role ``rspan`` a cell can be extended through
   additional rows

 * auto span rightmost cell of a table row over the missing cells on the right
   side of that table-row.  With Option ``:fill-cells:`` this behavior can
   changed from *auto span* to *auto fill*, which automatically inserts (empty)
   cells instead of spanning the last cell.

 options:

 * ``:header-rows:``   [int] count of header rows
 * ``:stub-columns:``  [int] count of stub columns
 * ``:widths:``        [[int] [int] ... ] widths of columns
 * ``:fill-cells:``    instead of auto-spanning missing cells, insert missing cells

 roles:

 * ``:cspan:`` [int] additional columns (*morecols*)
 * ``:rspan:`` [int] additional rows (*morerows*)

 The example below shows how to use this markup.  The first level of the staged
 list is the *table-row*. In the *table-row* there is only one markup allowed,
 the list of the cells in this *table-row*. Exceptions are *comments* ( ``..`` )
 and *targets* (e.g. a ref to ``:ref:`last row <last row>``` / :ref:`last row
 <last row>`).

 .. code-block:: rst

    .. flat-table:: table title
       :widths: 2 1 1 3

       * - head col 1
         - head col 2
         - head col 3
         - head col 4

       * - column 1
         - field 1.1
         - field 1.2 with autospan

       * - column 2
         - field 2.1
         - :rspan:`1` :cspan:`1` field 2.2 - 3.3

       * .. _`last row`:

         - column 3

 Rendered as:

    .. flat-table:: table title
       :widths: 2 1 1 3

       * - head col 1
         - head col 2
         - head col 3
         - head col 4

       * - column 1
         - field 1.1
         - field 1.2 with autospan

       * - column 2
         - field 2.1
         - :rspan:`1` :cspan:`1` field 2.2 - 3.3

       * .. _`last row`:

         - column 3
	Introduction
	============

	The Linux kernel uses `Sphinx`_ to generate pretty documentation from
	`reStructuredText`_ files under ``Documentation``. To build the documentation in
	HTML or PDF formats, use ``make htmldocs`` or ``make pdfdocs``. The generated
	documentation is placed in ``Documentation/output``.

	.. _Sphinx: http://www.sphinx-doc.org/
	.. _reStructuredText: http://docutils.sourceforge.net/rst.html

	The reStructuredText files may contain directives to include structured
	documentation comments, or kernel-doc comments, from source files. Usually these
	are used to describe the functions and types and design of the code. The
	kernel-doc comments have some special structure and formatting, but beyond that
	they are also treated as reStructuredText.

	There is also the deprecated DocBook toolchain to generate documentation from
	DocBook XML template files under ``Documentation/DocBook``. The DocBook files
	are to be converted to reStructuredText, and the toolchain is slated to be
	removed.

	Finally, there are thousands of plain text documentation files scattered around
	``Documentation``. Some of these will likely be converted to reStructuredText
	over time, but the bulk of them will remain in plain text.

	Sphinx Build
	============

	The usual way to generate the documentation is to run ``make htmldocs`` or
	``make pdfdocs``. There are also other formats available, see the documentation
	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, ``rst2pdf`` is also
	needed. 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.

	To remove the generated documentation, run ``make cleandocs``.

	Writing Documentation
	=====================

	Adding new documentation can be as simple as:

	1. Add a new ``.rst`` file somewhere under ``Documentation``.
	2. Refer to it from the Sphinx main `TOC tree`_ in ``Documentation/index.rst``.

	.. _TOC tree: http://www.sphinx-doc.org/en/stable/markup/toctree.html

	This is usually good enough for simple documentation (like the one you're
	reading right now), but for larger documents it may be advisable to create a
	subdirectory (or use an existing one). For example, the graphics subsystem
	documentation is under ``Documentation/gpu``, split to several ``.rst`` files,
	and has a separate ``index.rst`` (with a ``toctree`` of its own) referenced from
	the main index.

	See the documentation for `Sphinx`_ and `reStructuredText`_ on what you can do
	with them. In particular, the Sphinx `reStructuredText Primer`_ is a good place
	to get started with reStructuredText. There are also some `Sphinx specific
	markup constructs`_.

	.. _reStructuredText Primer: http://www.sphinx-doc.org/en/stable/rest.html
	.. _Sphinx specific markup constructs: http://www.sphinx-doc.org/en/stable/markup/index.html

	Specific guidelines for the kernel documentation
	------------------------------------------------

	Here are some specific guidelines for the kernel documentation:

	* Please don't go overboard with reStructuredText markup. Keep it simple.

	* Please stick to this order of heading adornments:

	1. ``=`` with overline for document title::

	==============
	Document title
	==============

	2. ``=`` for chapters::

	Chapters
	========

	3. ``-`` for sections::

	Section
	-------

	4. ``~`` for subsections::

	Subsection
	~~~~~~~~~~

	Although RST doesn't mandate a specific order ("Rather than imposing a fixed
	number and order of section title adornment styles, the order enforced will be
	the order as encountered."), having the higher levels the same overall makes
	it easier to follow the documents.


	the C domain
	------------

	The `Sphinx C Domain`_ (name c) is suited for documentation of C API. E.g. a
	function prototype:

	.. code-block:: rst

	.. c:function:: int ioctl( int fd, int request )

	The C domain of the kernel-doc has some additional features. E.g. you can
	rename the reference name of a function with a common name like ``open`` or
	``ioctl``:

	.. code-block:: rst

	.. c:function:: int ioctl( int fd, int request )
	:name: VIDIOC_LOG_STATUS

	The func-name (e.g. ioctl) remains in the output but the ref-name changed from
	``ioctl`` to ``VIDIOC_LOG_STATUS``. The index entry for this function is also
	changed to ``VIDIOC_LOG_STATUS`` and the function can now referenced by:

	.. code-block:: rst

	:c:func:`VIDIOC_LOG_STATUS`


	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 ``flat-table`` is a double-stage list similar to the ``list-table`` with
	some additional features:

	* column-span: with the role ``cspan`` a cell can be extended through
	additional columns

	* row-span: with the role ``rspan`` a cell can be extended through
	additional rows

	* auto span rightmost cell of a table row over the missing cells on the right
	side of that table-row. With Option ``:fill-cells:`` this behavior can
	changed from auto span to auto fill, which automatically inserts (empty)
	cells instead of spanning the last cell.

	options:

	* ``:header-rows:`` [int] count of header rows
	* ``:stub-columns:`` [int] count of stub columns
	* ``:widths:`` [[int] [int] ... ] widths of columns
	* ``:fill-cells:`` instead of auto-spanning missing cells, insert missing cells

	roles:

	* ``:cspan:`` [int] additional columns (morecols)
	* ``:rspan:`` [int] additional rows (morerows)

	The example below shows how to use this markup. The first level of the staged
	list is the table-row. In the table-row there is only one markup allowed,
	the list of the cells in this table-row. Exceptions are comments ( ``..`` )
	and targets (e.g. a ref to ``:ref:`last row <last row>``` / :ref:`last row
	<last row>`).

	.. code-block:: rst

	.. flat-table:: table title
	:widths: 2 1 1 3

	* - head col 1
	- head col 2
	- head col 3
	- head col 4

	* - column 1
	- field 1.1
	- field 1.2 with autospan

	* - column 2
	- field 2.1
	- :rspan:`1` :cspan:`1` field 2.2 - 3.3

	* .. _`last row`:

	- column 3

	Rendered as:

	.. flat-table:: table title
	:widths: 2 1 1 3

	* - head col 1
	- head col 2
	- head col 3
	- head col 4

	* - column 1
	- field 1.1
	- field 1.2 with autospan

	* - column 2
	- field 2.1
	- :rspan:`1` :cspan:`1` field 2.2 - 3.3

	* .. _`last row`:

	- column 3