+++ /dev/null
-=================================
-How to write kernel documentation
-=================================
-
-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
-
-
-Including kernel-doc comments
-=============================
-
-The Linux kernel source files may contain structured documentation comments, or
-kernel-doc comments to describe the functions and types and design of the
-code. The documentation comments may be included to any of the reStructuredText
-documents using a dedicated kernel-doc Sphinx directive extension.
-
-The kernel-doc directive is of the format::
-
- .. kernel-doc:: source
- :option:
-
-The *source* is the path to a source file, relative to the kernel source
-tree. The following directive options are supported:
-
-export: *[source-pattern ...]*
- Include documentation for all functions in *source* that have been exported
- using ``EXPORT_SYMBOL`` or ``EXPORT_SYMBOL_GPL`` either in *source* or in any
- of the files specified by *source-pattern*.
-
- The *source-pattern* is useful when the kernel-doc comments have been placed
- in header files, while ``EXPORT_SYMBOL`` and ``EXPORT_SYMBOL_GPL`` are next to
- the function definitions.
-
- Examples::
-
- .. kernel-doc:: lib/bitmap.c
- :export:
-
- .. kernel-doc:: include/net/mac80211.h
- :export: net/mac80211/*.c
-
-internal: *[source-pattern ...]*
- Include documentation for all functions and types in *source* that have
- **not** been exported using ``EXPORT_SYMBOL`` or ``EXPORT_SYMBOL_GPL`` either
- in *source* or in any of the files specified by *source-pattern*.
-
- Example::
-
- .. kernel-doc:: drivers/gpu/drm/i915/intel_audio.c
- :internal:
-
-doc: *title*
- Include documentation for the ``DOC:`` paragraph identified by *title* in
- *source*. Spaces are allowed in *title*; do not quote the *title*. The *title*
- is only used as an identifier for the paragraph, and is not included in the
- output. Please make sure to have an appropriate heading in the enclosing
- reStructuredText document.
-
- Example::
-
- .. kernel-doc:: drivers/gpu/drm/i915/intel_audio.c
- :doc: High Definition Audio over HDMI and Display Port
-
-functions: *function* *[...]*
- Include documentation for each *function* in *source*.
-
- Example::
-
- .. kernel-doc:: lib/bitmap.c
- :functions: bitmap_parselist bitmap_parselist_user
-
-Without options, the kernel-doc directive includes all documentation comments
-from the source file.
-
-The kernel-doc extension is included in the kernel source tree, at
-``Documentation/sphinx/kernel-doc.py``. Internally, it uses the
-``scripts/kernel-doc`` script to extract the documentation comments from the
-source.
-
-.. _kernel_doc:
-
-Writing kernel-doc comments
-===========================
-
-In order to provide embedded, "C" friendly, easy to maintain, but consistent and
-extractable overview, function and type documentation, the Linux kernel has
-adopted a consistent style for documentation comments. The format for this
-documentation is called the kernel-doc format, described below. This style
-embeds the documentation within the source files, using a few simple conventions
-for adding documentation paragraphs and documenting functions and their
-parameters, structures and unions and their members, enumerations, and typedefs.
-
-.. note:: The kernel-doc format is deceptively similar to gtk-doc or Doxygen,
- yet distinctively different, for historical reasons. The kernel source
- contains tens of thousands of kernel-doc comments. Please stick to the style
- described here.
-
-The ``scripts/kernel-doc`` script is used by the Sphinx kernel-doc extension in
-the documentation build to extract this embedded documentation into the various
-HTML, PDF, and other format documents.
-
-In order to provide good documentation of kernel functions and data structures,
-please use the following conventions to format your kernel-doc comments in the
-Linux kernel source.
-
-How to format kernel-doc comments
----------------------------------
-
-The opening comment mark ``/**`` is reserved for kernel-doc comments. Only
-comments so marked will be considered by the ``kernel-doc`` tool. Use it only
-for comment blocks that contain kernel-doc formatted comments. The usual ``*/``
-should be used as the closing comment marker. The lines in between should be
-prefixed by `` * `` (space star space).
-
-The function and type kernel-doc comments should be placed just before the
-function or type being described. The overview kernel-doc comments may be freely
-placed at the top indentation level.
-
-Example kernel-doc function comment::
-
- /**
- * foobar() - Brief description of foobar.
- * @arg: Description of argument of foobar.
- *
- * Longer description of foobar.
- *
- * Return: Description of return value of foobar.
- */
- int foobar(int arg)
-
-The format is similar for documentation for structures, enums, paragraphs,
-etc. See the sections below for details.
-
-The kernel-doc structure is extracted from the comments, and proper `Sphinx C
-Domain`_ function and type descriptions with anchors are generated for them. The
-descriptions are filtered for special kernel-doc highlights and
-cross-references. See below for details.
-
-.. _Sphinx C Domain: http://www.sphinx-doc.org/en/stable/domains.html
-
-Highlights and cross-references
--------------------------------
-
-The following special patterns are recognized in the kernel-doc comment
-descriptive text and converted to proper reStructuredText markup and `Sphinx C
-Domain`_ references.
-
-.. attention:: The below are **only** recognized within kernel-doc comments,
- **not** within normal reStructuredText documents.
-
-``funcname()``
- Function reference.
-
-``@parameter``
- Name of a function parameter. (No cross-referencing, just formatting.)
-
-``%CONST``
- Name of a constant. (No cross-referencing, just formatting.)
-
-``$ENVVAR``
- Name of an environment variable. (No cross-referencing, just formatting.)
-
-``&struct name``
- Structure reference.
-
-``&enum name``
- Enum reference.
-
-``&typedef name``
- Typedef reference.
-
-``&struct_name->member`` or ``&struct_name.member``
- Structure or union member reference. The cross-reference will be to the struct
- or union definition, not the member directly.
-
-``&name``
- A generic type reference. Prefer using the full reference described above
- instead. This is mostly for legacy comments.
-
-Cross-referencing from reStructuredText
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-
-To cross-reference the functions and types defined in the kernel-doc comments
-from reStructuredText documents, please use the `Sphinx C Domain`_
-references. For example::
-
- See function :c:func:`foo` and struct/union/enum/typedef :c:type:`bar`.
-
-While the type reference works with just the type name, without the
-struct/union/enum/typedef part in front, you may want to use::
-
- See :c:type:`struct foo <foo>`.
- See :c:type:`union bar <bar>`.
- See :c:type:`enum baz <baz>`.
- See :c:type:`typedef meh <meh>`.
-
-This will produce prettier links, and is in line with how kernel-doc does the
-cross-references.
-
-For further details, please refer to the `Sphinx C Domain`_ documentation.
-
-Function documentation
-----------------------
-
-The general format of a function and function-like macro kernel-doc comment is::
-
- /**
- * function_name() - Brief description of function.
- * @arg1: Describe the first argument.
- * @arg2: Describe the second argument.
- * One can provide multiple line descriptions
- * for arguments.
- *
- * A longer description, with more discussion of the function function_name()
- * that might be useful to those using or modifying it. Begins with an
- * empty comment line, and may include additional embedded empty
- * comment lines.
- *
- * The longer description may have multiple paragraphs.
- *
- * Return: Describe the return value of foobar.
- *
- * The return value description can also have multiple paragraphs, and should
- * be placed at the end of the comment block.
- */
-
-The brief description following the function name may span multiple lines, and
-ends with an ``@argument:`` description, a blank comment line, or the end of the
-comment block.
-
-The kernel-doc function comments describe each parameter to the function, in
-order, with the ``@argument:`` descriptions. The ``@argument:`` descriptions
-must begin on the very next line following the opening brief function
-description line, with no intervening blank comment lines. The ``@argument:``
-descriptions may span multiple lines. The continuation lines may contain
-indentation. If a function parameter is ``...`` (varargs), it should be listed
-in kernel-doc notation as: ``@...:``.
-
-The return value, if any, should be described in a dedicated section at the end
-of the comment starting with "Return:".
-
-Structure, union, and enumeration documentation
------------------------------------------------
-
-The general format of a struct, union, and enum kernel-doc comment is::
-
- /**
- * struct struct_name - Brief description.
- * @member_name: Description of member member_name.
- *
- * Description of the structure.
- */
-
-Below, "struct" is used to mean structs, unions and enums, and "member" is used
-to mean struct and union members as well as enumerations in an enum.
-
-The brief description following the structure name may span multiple lines, and
-ends with a ``@member:`` description, a blank comment line, or the end of the
-comment block.
-
-The kernel-doc data structure comments describe each member of the structure, in
-order, with the ``@member:`` descriptions. The ``@member:`` descriptions must
-begin on the very next line following the opening brief function description
-line, with no intervening blank comment lines. The ``@member:`` descriptions may
-span multiple lines. The continuation lines may contain indentation.
-
-In-line member documentation comments
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-
-The structure members may also be documented in-line within the definition::
-
- /**
- * struct foo - Brief description.
- * @foo: The Foo member.
- */
- struct foo {
- int foo;
- /**
- * @bar: The Bar member.
- */
- int bar;
- /**
- * @baz: The Baz member.
- *
- * Here, the member description may contain several paragraphs.
- */
- int baz;
- }
-
-Private members
-~~~~~~~~~~~~~~~
-
-Inside a struct description, you can use the "private:" and "public:" comment
-tags. Structure fields that are inside a "private:" area are not listed in the
-generated output documentation. The "private:" and "public:" tags must begin
-immediately following a ``/*`` comment marker. They may optionally include
-comments between the ``:`` and the ending ``*/`` marker.
-
-Example::
-
- /**
- * struct my_struct - short description
- * @a: first member
- * @b: second member
- *
- * Longer description
- */
- struct my_struct {
- int a;
- int b;
- /* private: internal use only */
- int c;
- };
-
-
-Typedef documentation
----------------------
-
-The general format of a typedef kernel-doc comment is::
-
- /**
- * typedef type_name - Brief description.
- *
- * Description of the type.
- */
-
-Overview documentation comments
--------------------------------
-
-To facilitate having source code and comments close together, you can include
-kernel-doc documentation blocks that are free-form comments instead of being
-kernel-doc for functions, structures, unions, enums, or typedefs. This could be
-used for something like a theory of operation for a driver or library code, for
-example.
-
-This is done by using a ``DOC:`` section keyword with a section title.
-
-The general format of an overview or high-level documentation comment is::
-
- /**
- * DOC: Theory of Operation
- *
- * The whizbang foobar is a dilly of a gizmo. It can do whatever you
- * want it to do, at any time. It reads your mind. Here's how it works.
- *
- * foo bar splat
- *
- * The only drawback to this gizmo is that is can sometimes damage
- * hardware, software, or its subject(s).
- */
-
-The title following ``DOC:`` acts as a heading within the source file, but also
-as an identifier for extracting the documentation comment. Thus, the title must
-be unique within the file.
-
-Recommendations
----------------
-
-We definitely need kernel-doc formatted documentation for functions that are
-exported to loadable modules using ``EXPORT_SYMBOL`` or ``EXPORT_SYMBOL_GPL``.
-
-We also look to provide kernel-doc formatted documentation for functions
-externally visible to other kernel files (not marked "static").
-
-We also recommend providing kernel-doc formatted documentation for private (file
-"static") routines, for consistency of kernel source code layout. But this is
-lower priority and at the discretion of the MAINTAINER of that kernel source
-file.
-
-Data structures visible in kernel include files should also be documented using
-kernel-doc formatted comments.
-
-DocBook XML [DEPRECATED]
-========================
-
-.. attention::
-
- This section describes the deprecated DocBook XML toolchain. Please do not
- create new DocBook XML template files. Please consider converting existing
- DocBook XML templates files to Sphinx/reStructuredText.
-
-Converting DocBook to Sphinx
-----------------------------
-
-Over time, we expect all of the documents under ``Documentation/DocBook`` to be
-converted to Sphinx and reStructuredText. For most DocBook XML documents, a good
-enough solution is to use the simple ``Documentation/sphinx/tmplcvt`` script,
-which uses ``pandoc`` under the hood. For example::
-
- $ cd Documentation/sphinx
- $ ./tmplcvt ../DocBook/in.tmpl ../out.rst
-
-Then edit the resulting rst files to fix any remaining issues, and add the
-document in the ``toctree`` in ``Documentation/index.rst``.
-
-Components of the kernel-doc system
------------------------------------
-
-Many places in the source tree have extractable documentation in the form of
-block comments above functions. The components of this system are:
-
-- ``scripts/kernel-doc``
-
- This is a perl script that hunts for the block comments and can mark them up
- directly into reStructuredText, DocBook, man, text, and HTML. (No, not
- texinfo.)
-
-- ``Documentation/DocBook/*.tmpl``
-
- These are XML template files, which are normal XML files with special
- place-holders for where the extracted documentation should go.
-
-- ``scripts/docproc.c``
-
- This is a program for converting XML template files into XML files. When a
- file is referenced it is searched for symbols exported (EXPORT_SYMBOL), to be
- able to distinguish between internal and external functions.
-
- It invokes kernel-doc, giving it the list of functions that are to be
- documented.
-
- Additionally it is used to scan the XML template files to locate all the files
- referenced herein. This is used to generate dependency information as used by
- make.
-
-- ``Makefile``
-
- The targets 'xmldocs', 'psdocs', 'pdfdocs', and 'htmldocs' are used to build
- DocBook XML files, PostScript files, PDF files, and html files in
- Documentation/DocBook. The older target 'sgmldocs' is equivalent to 'xmldocs'.
-
-- ``Documentation/DocBook/Makefile``
-
- This is where C files are associated with SGML templates.
-
-How to use kernel-doc comments in DocBook XML template files
-------------------------------------------------------------
-
-DocBook XML template files (\*.tmpl) are like normal XML files, except that they
-can contain escape sequences where extracted documentation should be inserted.
-
-``!E<filename>`` is replaced by the documentation, in ``<filename>``, for
-functions that are exported using ``EXPORT_SYMBOL``: the function list is
-collected from files listed in ``Documentation/DocBook/Makefile``.
-
-``!I<filename>`` is replaced by the documentation for functions that are **not**
-exported using ``EXPORT_SYMBOL``.
-
-``!D<filename>`` is used to name additional files to search for functions
-exported using ``EXPORT_SYMBOL``.
-
-``!F<filename> <function [functions...]>`` is replaced by the documentation, in
-``<filename>``, for the functions listed.
-
-``!P<filename> <section title>`` is replaced by the contents of the ``DOC:``
-section titled ``<section title>`` from ``<filename>``. Spaces are allowed in
-``<section title>``; do not quote the ``<section title>``.
-
-``!C<filename>`` is replaced by nothing, but makes the tools check that all DOC:
-sections and documented functions, symbols, etc. are used. This makes sense to
-use when you use ``!F`` or ``!P`` only and want to verify that all documentation
-is included.
git.samba.org / sfrench / cifs-2.6.git / blobdiff