diff options
Diffstat (limited to 'Documentation/doc-guide')
| -rw-r--r-- | Documentation/doc-guide/contributing.rst | 300 | ||||
| -rw-r--r-- | Documentation/doc-guide/index.rst | 2 | ||||
| -rw-r--r-- | Documentation/doc-guide/kernel-doc.rst | 103 | ||||
| -rw-r--r-- | Documentation/doc-guide/maintainer-profile.rst | 52 | ||||
| -rw-r--r-- | Documentation/doc-guide/parse-headers.rst | 4 | ||||
| -rw-r--r-- | Documentation/doc-guide/sphinx.rst | 203 |
6 files changed, 593 insertions, 71 deletions
diff --git a/Documentation/doc-guide/contributing.rst b/Documentation/doc-guide/contributing.rst new file mode 100644 index 000000000000..662c7a840cd5 --- /dev/null +++ b/Documentation/doc-guide/contributing.rst @@ -0,0 +1,300 @@ +.. SPDX-License-Identifier: GPL-2.0 + +How to help improve kernel documentation +======================================== + +Documentation is an important part of any software-development project. +Good documentation helps to bring new developers in and helps established +developers work more effectively. Without top-quality documentation, a lot +of time is wasted in reverse-engineering the code and making avoidable +mistakes. + +Unfortunately, the kernel's documentation currently falls far short of what +it needs to be to support a project of this size and importance. + +This guide is for contributors who would like to improve that situation. +Kernel documentation improvements can be made by developers at a variety of +skill levels; they are a relatively easy way to learn the kernel process in +general and find a place in the community. The bulk of what follows is the +documentation maintainer's list of tasks that most urgently need to be +done. + +The documentation TODO list +--------------------------- + +There is an endless list of tasks that need to be carried out to get our +documentation to where it should be. This list contains a number of +important items, but is far from exhaustive; if you see a different way to +improve the documentation, please do not hold back! + +Addressing warnings +~~~~~~~~~~~~~~~~~~~ + +The documentation build currently spews out an unbelievable number of +warnings. When you have that many, you might as well have none at all; +people ignore them, and they will never notice when their work adds new +ones. For this reason, eliminating warnings is one of the highest-priority +tasks on the documentation TODO list. The task itself is reasonably +straightforward, but it must be approached in the right way to be +successful. + +Warnings issued by a compiler for C code can often be dismissed as false +positives, leading to patches aimed at simply shutting the compiler up. +Warnings from the documentation build almost always point at a real +problem; making those warnings go away requires understanding the problem +and fixing it at its source. For this reason, patches fixing documentation +warnings should probably not say "fix a warning" in the changelog title; +they should indicate the real problem that has been fixed. + +Another important point is that documentation warnings are often created by +problems in kerneldoc comments in C code. While the documentation +maintainer appreciates being copied on fixes for these warnings, the +documentation tree is often not the right one to actually carry those +fixes; they should go to the maintainer of the subsystem in question. + +For example, in a documentation build I grabbed a pair of warnings nearly +at random:: + + ./drivers/devfreq/devfreq.c:1818: warning: bad line: + - Resource-managed devfreq_register_notifier() + ./drivers/devfreq/devfreq.c:1854: warning: bad line: + - Resource-managed devfreq_unregister_notifier() + +(The lines were split for readability). + +A quick look at the source file named above turned up a couple of kerneldoc +comments that look like this:: + + /** + * devm_devfreq_register_notifier() + - Resource-managed devfreq_register_notifier() + * @dev: The devfreq user device. (parent of devfreq) + * @devfreq: The devfreq object. + * @nb: The notifier block to be unregistered. + * @list: DEVFREQ_TRANSITION_NOTIFIER. + */ + +The problem is the missing "*", which confuses the build system's +simplistic idea of what C comment blocks look like. This problem had been +present since that comment was added in 2016 — a full four years. Fixing +it was a matter of adding the missing asterisks. A quick look at the +history for that file showed what the normal format for subject lines is, +and ``scripts/get_maintainer.pl`` told me who should receive it (pass paths to +your patches as arguments to scripts/get_maintainer.pl). The resulting patch +looked like this:: + + [PATCH] PM / devfreq: Fix two malformed kerneldoc comments + + Two kerneldoc comments in devfreq.c fail to adhere to the required format, + resulting in these doc-build warnings: + + ./drivers/devfreq/devfreq.c:1818: warning: bad line: + - Resource-managed devfreq_register_notifier() + ./drivers/devfreq/devfreq.c:1854: warning: bad line: + - Resource-managed devfreq_unregister_notifier() + + Add a couple of missing asterisks and make kerneldoc a little happier. + + Signed-off-by: Jonathan Corbet <corbet@lwn.net> + --- + drivers/devfreq/devfreq.c | 4 ++-- + 1 file changed, 2 insertions(+), 2 deletions(-) + + diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c + index 57f6944d65a6..00c9b80b3d33 100644 + --- a/drivers/devfreq/devfreq.c + +++ b/drivers/devfreq/devfreq.c + @@ -1814,7 +1814,7 @@ static void devm_devfreq_notifier_release(struct device *dev, void *res) + + /** + * devm_devfreq_register_notifier() + - - Resource-managed devfreq_register_notifier() + + * - Resource-managed devfreq_register_notifier() + * @dev: The devfreq user device. (parent of devfreq) + * @devfreq: The devfreq object. + * @nb: The notifier block to be unregistered. + @@ -1850,7 +1850,7 @@ EXPORT_SYMBOL(devm_devfreq_register_notifier); + + /** + * devm_devfreq_unregister_notifier() + - - Resource-managed devfreq_unregister_notifier() + + * - Resource-managed devfreq_unregister_notifier() + * @dev: The devfreq user device. (parent of devfreq) + * @devfreq: The devfreq object. + * @nb: The notifier block to be unregistered. + -- + 2.24.1 + +The entire process only took a few minutes. Of course, I then found that +somebody else had fixed it in a separate tree, highlighting another lesson: +always check linux-next to see if a problem has been fixed before you dig +into it. + +Other fixes will take longer, especially those relating to structure +members or function parameters that lack documentation. In such cases, it +is necessary to work out what the role of those members or parameters is +and describe them correctly. Overall, this task gets a little tedious at +times, but it's highly important. If we can actually eliminate warnings +from the documentation build, then we can start expecting developers to +avoid adding new ones. + +In addition to warnings from the regular documentation build, you can also +run ``make refcheckdocs`` to find references to nonexistent documentation +files. + +Languishing kerneldoc comments +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +Developers are encouraged to write kerneldoc comments for their code, but +many of those comments are never pulled into the docs build. That makes +this information harder to find and, for example, makes Sphinx unable to +generate links to that documentation. Adding ``kernel-doc`` directives to +the documentation to bring those comments in can help the community derive +the full value of the work that has gone into creating them. + +The ``scripts/find-unused-docs.sh`` tool can be used to find these +overlooked comments. + +Note that the most value comes from pulling in the documentation for +exported functions and data structures. Many subsystems also have +kerneldoc comments for internal use; those should not be pulled into the +documentation build unless they are placed in a document that is +specifically aimed at developers working within the relevant subsystem. + + +Typo fixes +~~~~~~~~~~ + +Fixing typographical or formatting errors in the documentation is a quick +way to figure out how to create and send patches, and it is a useful +service. I am always willing to accept such patches. That said, once you +have fixed a few, please consider moving on to more advanced tasks, leaving +some typos for the next beginner to address. + +Please note that some things are *not* typos and should not be "fixed": + + - Both American and British English spellings are allowed within the + kernel documentation. There is no need to fix one by replacing it with + the other. + + - The question of whether a period should be followed by one or two spaces + is not to be debated in the context of kernel documentation. Other + areas of rational disagreement, such as the "Oxford comma", are also + off-topic here. + +As with any patch to any project, please consider whether your change is +really making things better. + +Ancient documentation +~~~~~~~~~~~~~~~~~~~~~ + +Some kernel documentation is current, maintained, and useful. Some +documentation is ... not. Dusty, old, and inaccurate documentation can +mislead readers and casts doubt on our documentation as a whole. Anything +that can be done to address such problems is more than welcome. + +Whenever you are working with a document, please consider whether it is +current, whether it needs updating, or whether it should perhaps be removed +altogether. There are a number of warning signs that you can pay attention +to here: + + - References to 2.x kernels + - Pointers to SourceForge repositories + - Nothing but typo fixes in the history for several years + - Discussion of pre-Git workflows + +The best thing to do, of course, would be to bring the documentation +current, adding whatever information is needed. Such work often requires +the cooperation of developers familiar with the subsystem in question, of +course. Developers are often more than willing to cooperate with people +working to improve the documentation when asked nicely, and when their +answers are listened to and acted upon. + +Some documentation is beyond hope; we occasionally find documents that +refer to code that was removed from the kernel long ago, for example. +There is surprising resistance to removing obsolete documentation, but we +should do that anyway. Extra cruft in our documentation helps nobody. + +In cases where there is perhaps some useful information in a badly outdated +document, and you are unable to update it, the best thing to do may be to +add a warning at the beginning. The following text is recommended:: + + .. warning :: + This document is outdated and in need of attention. Please use + this information with caution, and please consider sending patches + to update it. + +That way, at least our long-suffering readers have been warned that the +document may lead them astray. + +Documentation coherency +~~~~~~~~~~~~~~~~~~~~~~~ + +The old-timers around here will remember the Linux books that showed up on +the shelves in the 1990s. They were simply collections of documentation +files scrounged from various locations on the net. The books have (mostly) +improved since then, but the kernel's documentation is still mostly built +on that model. It is thousands of files, almost each of which was written +in isolation from all of the others. We don't have a coherent body of +kernel documentation; we have thousands of individual documents. + +We have been trying to improve the situation through the creation of +a set of "books" that group documentation for specific readers. These +include: + + - Documentation/admin-guide/index.rst + - Documentation/core-api/index.rst + - Documentation/driver-api/index.rst + - Documentation/userspace-api/index.rst + +As well as this book on documentation itself. + +Moving documents into the appropriate books is an important task and needs +to continue. There are a couple of challenges associated with this work, +though. Moving documentation files creates short-term pain for the people +who work with those files; they are understandably unenthusiastic about +such changes. Usually the case can be made to move a document once; we +really don't want to keep shifting them around, though. + +Even when all documents are in the right place, though, we have only +managed to turn a big pile into a group of smaller piles. The work of +trying to knit all of those documents together into a single whole has not +yet begun. If you have bright ideas on how we could proceed on that front, +we would be more than happy to hear them. + +Stylesheet improvements +~~~~~~~~~~~~~~~~~~~~~~~ + +With the adoption of Sphinx we have much nicer-looking HTML output than we +once did. But it could still use a lot of improvement; Donald Knuth and +Edward Tufte would be unimpressed. That requires tweaking our stylesheets +to create more typographically sound, accessible, and readable output. + +Be warned: if you take on this task you are heading into classic bikeshed +territory. Expect a lot of opinions and discussion for even relatively +obvious changes. That is, alas, the nature of the world we live in. + +Non-LaTeX PDF build +~~~~~~~~~~~~~~~~~~~ + +This is a decidedly nontrivial task for somebody with a lot of time and +Python skills. The Sphinx toolchain is relatively small and well +contained; it is easy to add to a development system. But building PDF or +EPUB output requires installing LaTeX, which is anything but small or well +contained. That would be a nice thing to eliminate. + +The original hope had been to use the rst2pdf tool (https://rst2pdf.org/) +for PDF generation, but it turned out to not be up to the task. +Development work on rst2pdf seems to have picked up again in recent times, +though, which is a hopeful sign. If a suitably motivated developer were to +work with that project to make rst2pdf work with the kernel documentation +build, the world would be eternally grateful. + +Write more documentation +~~~~~~~~~~~~~~~~~~~~~~~~ + +Naturally, there are massive parts of the kernel that are severely +underdocumented. If you have the knowledge to document a specific kernel +subsystem and the desire to do so, please do not hesitate to do some +writing and contribute the result to the kernel. Untold numbers of kernel +developers and users will thank you. diff --git a/Documentation/doc-guide/index.rst b/Documentation/doc-guide/index.rst index 603f3ff55d5a..7c7d97784626 100644 --- a/Documentation/doc-guide/index.rst +++ b/Documentation/doc-guide/index.rst @@ -10,6 +10,8 @@ How to write kernel documentation sphinx kernel-doc parse-headers + contributing + maintainer-profile .. only:: subproject and html diff --git a/Documentation/doc-guide/kernel-doc.rst b/Documentation/doc-guide/kernel-doc.rst index fff6604631ea..d6f7efefea42 100644 --- a/Documentation/doc-guide/kernel-doc.rst +++ b/Documentation/doc-guide/kernel-doc.rst @@ -1,3 +1,6 @@ +.. title:: Kernel-doc comments + +=========================== Writing kernel-doc comments =========================== @@ -11,6 +14,9 @@ when it is embedded in source files. reasons. The kernel source contains tens of thousands of kernel-doc comments. Please stick to the style described here. +.. note:: kernel-doc does not cover Rust code: please see + Documentation/rust/general-information.rst instead. + The kernel-doc structure is extracted from the comments, and proper `Sphinx C Domain`_ function and type descriptions with anchors are generated from them. The descriptions are filtered for special kernel-doc @@ -145,9 +151,9 @@ named ``Return``. line breaks, so if you try to format some text nicely, as in:: * Return: - * 0 - OK - * -EINVAL - invalid argument - * -ENOMEM - out of memory + * %0 - OK + * %-EINVAL - invalid argument + * %-ENOMEM - out of memory this will all run together and produce:: @@ -157,8 +163,8 @@ named ``Return``. ReST list, e. g.:: * Return: - * * 0 - OK to runtime suspend the device - * * -EBUSY - Device should not be runtime suspended + * * %0 - OK to runtime suspend the device + * * %-EBUSY - Device should not be runtime suspended #) If the descriptive text you provide has lines that begin with some phrase followed by a colon, each of those phrases will be taken @@ -247,12 +253,12 @@ It is possible to document nested structs and unions, like:: struct { int memb1; int memb2; - } + }; struct { void *memb3; int memb4; - } - } + }; + }; union { struct { int memb1; @@ -335,6 +341,51 @@ Typedefs with function prototypes can also be documented:: */ typedef void (*type_name)(struct v4l2_ctrl *arg1, void *arg2); +Object-like macro documentation +------------------------------- + +Object-like macros are distinct from function-like macros. They are +differentiated by whether the macro name is immediately followed by a +left parenthesis ('(') for function-like macros or not followed by one +for object-like macros. + +Function-like macros are handled like functions by ``scripts/kernel-doc``. +They may have a parameter list. Object-like macros have do not have a +parameter list. + +The general format of an object-like macro kernel-doc comment is:: + + /** + * define object_name - Brief description. + * + * Description of the object. + */ + +Example:: + + /** + * define MAX_ERRNO - maximum errno value that is supported + * + * Kernel pointers have redundant information, so we can use a + * scheme where we can return either an error code or a normal + * pointer with the same return value. + */ + #define MAX_ERRNO 4095 + +Example:: + + /** + * define DRM_GEM_VRAM_PLANE_HELPER_FUNCS - \ + * Initializes struct drm_plane_helper_funcs for VRAM handling + * + * This macro initializes struct drm_plane_helper_funcs to use the + * respective helper functions. + */ + #define DRM_GEM_VRAM_PLANE_HELPER_FUNCS \ + .prepare_fb = drm_gem_vram_plane_helper_prepare_fb, \ + .cleanup_fb = drm_gem_vram_plane_helper_cleanup_fb + + Highlights and cross-references ------------------------------- @@ -387,22 +438,23 @@ Domain`_ references. 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`. +No additional syntax is needed to cross-reference the functions and types +defined in the kernel-doc comments from reStructuredText documents. +Just end function names with ``()`` and write ``struct``, ``union``, ``enum`` +or ``typedef`` before types. +For example:: -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 foo(). + See struct foo. + See union bar. + See enum baz. + See typedef meh. - See :c:type:`struct foo <foo>`. - See :c:type:`union bar <bar>`. - See :c:type:`enum baz <baz>`. - See :c:type:`typedef meh <meh>`. +However, if you want custom text in the cross-reference link, that can be done +through the following syntax:: -This will produce prettier links, and is in line with how kernel-doc does the -cross-references. + See :c:func:`my custom link text for function foo <foo>`. + See :c:type:`my custom link text for struct bar <bar>`. For further details, please refer to the `Sphinx C Domain`_ documentation. @@ -435,6 +487,7 @@ 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. +============================= Including kernel-doc comments ============================= @@ -489,6 +542,14 @@ identifiers: *[ function/type ...]* .. kernel-doc:: lib/idr.c :identifiers: +no-identifiers: *[ function/type ...]* + Exclude documentation for each *function* and *type* in *source*. + + Example:: + + .. kernel-doc:: lib/bitmap.c + :no-identifiers: bitmap_parselist + functions: *[ function/type ...]* This is an alias of the 'identifiers' directive and deprecated. diff --git a/Documentation/doc-guide/maintainer-profile.rst b/Documentation/doc-guide/maintainer-profile.rst new file mode 100644 index 000000000000..db3636d0d71d --- /dev/null +++ b/Documentation/doc-guide/maintainer-profile.rst @@ -0,0 +1,52 @@ +.. SPDX-License-Identifier: GPL-2.0 + +Documentation subsystem maintainer entry profile +================================================ + +The documentation "subsystem" is the central coordinating point for the +kernel's documentation and associated infrastructure. It covers the +hierarchy under Documentation/ (with the exception of +Documentation/devicetree), various utilities under scripts/ and, at least +some of the time, LICENSES/. + +It's worth noting, though, that the boundaries of this subsystem are rather +fuzzier than normal. Many other subsystem maintainers like to keep control +of portions of Documentation/, and many more freely apply changes there +when it is convenient. Beyond that, much of the kernel's documentation is +found in the source as kerneldoc comments; those are usually (but not +always) maintained by the relevant subsystem maintainer. + +The mailing list for documentation is linux-doc@vger.kernel.org. Patches +should be made against the docs-next tree whenever possible. + +Submit checklist addendum +------------------------- + +When making documentation changes, you should actually build the +documentation and ensure that no new errors or warnings have been +introduced. Generating HTML documents and looking at the result will help +to avoid unsightly misunderstandings about how things will be rendered. + +All new documentation (including additions to existing documents) should +ideally justify who the intended target audience is somewhere in the +changelog; this way, we ensure that the documentation ends up in the correct +place. Some possible categories are: kernel developers (experts or +beginners), userspace programmers, end users and/or system administrators, +and distributors. + +Key cycle dates +--------------- + +Patches can be sent anytime, but response will be slower than usual during +the merge window. The docs tree tends to close late before the merge +window opens, since the risk of regressions from documentation patches is +low. + +Review cadence +-------------- + +I am the sole maintainer for the documentation subsystem, and I am doing +the work on my own time, so the response to patches will occasionally be +slow. I try to always send out a notification when a patch is merged (or +when I decide that one cannot be). Do not hesitate to send a ping if you +have not heard back within a week of sending a patch. diff --git a/Documentation/doc-guide/parse-headers.rst b/Documentation/doc-guide/parse-headers.rst index 24cfaa15dd81..5da0046f7059 100644 --- a/Documentation/doc-guide/parse-headers.rst +++ b/Documentation/doc-guide/parse-headers.rst @@ -10,7 +10,7 @@ if a symbol is not found at the documentation. That helps to keep the uAPI documentation in sync with the Kernel changes. The :ref:`parse_headers.pl <parse_headers>` provide a way to generate such cross-references. It has to be called via Makefile, while building the -documentation. Please see ``Documentation/media/Makefile`` for an example +documentation. Please see ``Documentation/userspace-api/media/Makefile`` for an example about how to use it inside the Kernel tree. .. _parse_headers: @@ -186,7 +186,7 @@ COPYRIGHT Copyright (c) 2016 by Mauro Carvalho Chehab <mchehab+samsung@kernel.org>. -License GPLv2: GNU GPL version 2 <http://gnu.org/licenses/gpl.html>. +License GPLv2: GNU GPL version 2 <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. diff --git a/Documentation/doc-guide/sphinx.rst b/Documentation/doc-guide/sphinx.rst index f71ddd592aaa..8081ebfe48bc 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 2.4.4 or higher. There's a script that checks for the Sphinx requirements. Please see :ref:`sphinx-pre-install` for further details. @@ -43,25 +44,18 @@ 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 in separate, + 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 work, - those expressions are written using LaTeX notation. It needs texlive - installed with amdfonts and amsmath in order to evaluate them. - -In summary, if you want to install Sphinx version 1.7.9, you should do:: +In summary, if you want to install the latest version of Sphinx, you +should do:: - $ virtualenv sphinx_1.7.9 - $ . sphinx_1.7.9/bin/activate - (sphinx_1.7.9) $ pip install -r Documentation/sphinx/requirements.txt + $ virtualenv sphinx_latest + $ . sphinx_latest/bin/activate + (sphinx_latest) $ 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 +64,7 @@ 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 +74,7 @@ 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. @@ -89,12 +82,33 @@ 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:: @@ -104,8 +118,8 @@ command line options for your distro:: 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. @@ -128,22 +142,71 @@ 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 +``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 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. + +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 +283,7 @@ 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 +313,24 @@ 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: @@ -303,17 +374,17 @@ and *targets* (e.g. a ref to ``:ref:`last row <last row>``` / :ref:`last row - head col 3 - head col 4 - * - column 1 + * - row 1 - field 1.1 - field 1.2 with autospan - * - column 2 + * - row 2 - field 2.1 - :rspan:`1` :cspan:`1` field 2.2 - 3.3 * .. _`last row`: - - column 3 + - row 3 Rendered as: @@ -325,17 +396,53 @@ Rendered as: - head col 3 - head col 4 - * - column 1 + * - row 1 - field 1.1 - field 1.2 with autospan - * - column 2 + * - row 2 - field 2.1 - :rspan:`1` :cspan:`1` field 2.2 - 3.3 * .. _`last row`: - - column 3 + - row 3 + +Cross-referencing +----------------- + +Cross-referencing from one documentation page to another can be done simply by +writing the path to the document file, no special syntax required. The path can +be either absolute or relative. For absolute paths, start it with +"Documentation/". For example, to cross-reference to this page, all the +following are valid options, depending on the current document's directory (note +that the ``.rst`` extension is required):: + + See Documentation/doc-guide/sphinx.rst. This always works. + Take a look at sphinx.rst, which is at this same directory. + Read ../sphinx.rst, which is one directory above. + +If you want the link to have a different rendered text other than the document's +title, you need to use Sphinx's ``doc`` role. For example:: + + See :doc:`my custom link text for document sphinx <sphinx>`. + +For most use cases, the former is preferred, as it is cleaner and more suited +for people reading the source files. If you come across a ``:doc:`` usage that +isn't adding any value, please feel free to convert it to just the document +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: @@ -344,7 +451,7 @@ Figures & Images If you want to add an image, you should use the ``kernel-figure`` and ``kernel-image`` directives. E.g. to insert a figure with a scalable -image format use SVG (:ref:`svg_image_example`):: +image format, use SVG (:ref:`svg_image_example`):: .. kernel-figure:: svg_image.svg :alt: simple SVG image @@ -358,7 +465,7 @@ image format use SVG (:ref:`svg_image_example`):: SVG image example -The kernel figure (and image) directive support **DOT** formated files, see +The kernel figure (and image) directive supports **DOT** formatted files, see * DOT: http://graphviz.org/pdf/dotguide.pdf * Graphviz: http://www.graphviz.org/content/dot-language @@ -377,7 +484,7 @@ A simple example (:ref:`hello_dot_file`):: DOT's hello world example -Embed *render* markups (or languages) like Graphviz's **DOT** is provided by the +Embedded *render* markups (or languages) like Graphviz's **DOT** are provided by the ``kernel-render`` directives.:: .. kernel-render:: DOT @@ -389,7 +496,7 @@ Embed *render* markups (or languages) like Graphviz's **DOT** is provided by the } How this will be rendered depends on the installed tools. If Graphviz is -installed, you will see an vector image. If not the raw markup is inserted as +installed, you will see a vector image. If not, the raw markup is inserted as *literal-block* (:ref:`hello_dot_render`). .. _hello_dot_render: @@ -404,8 +511,8 @@ installed, you will see an vector image. If not the raw markup is inserted as The *render* directive has all the options known from the *figure* directive, plus option ``caption``. If ``caption`` has a value, a *figure* node is -inserted. If not, a *image* node is inserted. A ``caption`` is also needed, if -you want to refer it (:ref:`hello_svg_render`). +inserted. If not, an *image* node is inserted. A ``caption`` is also needed, if +you want to refer to it (:ref:`hello_svg_render`). Embedded **SVG**:: |