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| -rw-r--r-- | Documentation/doc-guide/kernel-doc.rst | 545 | ||||
| -rw-r--r-- | Documentation/doc-guide/maintainer-profile.rst | 45 | ||||
| -rw-r--r-- | Documentation/doc-guide/parse-headers.rst | 192 | ||||
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diff --git a/Documentation/doc-guide/contributing.rst b/Documentation/doc-guide/contributing.rst new file mode 100644 index 000000000..67ee3691f --- /dev/null +++ b/Documentation/doc-guide/contributing.rst @@ -0,0 +1,295 @@ +.. 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. 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. + +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: + + - :doc:`../admin-guide/index` + - :doc:`../core-api/index` + - :doc:`../driver-api/index` + - :doc:`../userspace-api/index` + +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/hello.dot b/Documentation/doc-guide/hello.dot new file mode 100644 index 000000000..504621dfc --- /dev/null +++ b/Documentation/doc-guide/hello.dot @@ -0,0 +1,3 @@ +graph G { + Hello -- World +} diff --git a/Documentation/doc-guide/index.rst b/Documentation/doc-guide/index.rst new file mode 100644 index 000000000..7c7d97784 --- /dev/null +++ b/Documentation/doc-guide/index.rst @@ -0,0 +1,21 @@ +.. _doc_guide: + +================================= +How to write kernel documentation +================================= + +.. toctree:: + :maxdepth: 1 + + sphinx + kernel-doc + parse-headers + contributing + maintainer-profile + +.. only:: subproject and html + + Indices + ======= + + * :ref:`genindex` diff --git a/Documentation/doc-guide/kernel-doc.rst b/Documentation/doc-guide/kernel-doc.rst new file mode 100644 index 000000000..52a87ab4c --- /dev/null +++ b/Documentation/doc-guide/kernel-doc.rst @@ -0,0 +1,545 @@ +Writing kernel-doc comments +=========================== + +The Linux kernel source files may contain structured documentation +comments in the kernel-doc format to describe the functions, types +and design of the code. It is easier to keep documentation up-to-date +when it is embedded in source files. + +.. note:: The kernel-doc format is deceptively similar to javadoc, + 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 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 +highlights and cross-references. See below for details. + +.. _Sphinx C Domain: http://www.sphinx-doc.org/en/stable/domains.html + +Every function that is exported to loadable modules using +``EXPORT_SYMBOL`` or ``EXPORT_SYMBOL_GPL`` should have a kernel-doc +comment. Functions and data structures in header files which are intended +to be used by modules should also have kernel-doc comments. + +It is good practice to also 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. This is lower priority and at the discretion +of the maintainer of that kernel source file. + +How to format kernel-doc comments +--------------------------------- + +The opening comment mark ``/**`` is used for kernel-doc comments. The +``kernel-doc`` tool will extract comments marked this way. The rest of +the comment is formatted like a normal multi-line comment with a column +of asterisks on the left side, closing with ``*/`` on a line by itself. + +The function and type kernel-doc comments should be placed just before +the function or type being described in order to maximise the chance +that somebody changing the code will also change the documentation. The +overview kernel-doc comments may be placed anywhere at the top indentation +level. + +Running the ``kernel-doc`` tool with increased verbosity and without actual +output generation may be used to verify proper formatting of the +documentation comments. For example:: + + scripts/kernel-doc -v -none drivers/foo/bar.c + +The documentation format is verified by the kernel build when it is +requested to perform extra gcc checks:: + + make W=n + +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. + * + * Context: Describes whether the function can sleep, what locks it takes, + * releases, or expects to be held. It can extend over multiple + * lines. + * Return: Describe the return value of function_name. + * + * 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. + +Function parameters +~~~~~~~~~~~~~~~~~~~ + +Each function argument should be described in order, immediately following +the short function description. Do not leave a blank line between the +function description and the arguments, nor between the arguments. + +Each ``@argument:`` description may span multiple lines. + +.. note:: + + If the ``@argument`` description has multiple lines, the continuation + of the description should start at the same column as the previous line:: + + * @argument: some long description + * that continues on next lines + + or:: + + * @argument: + * some long description + * that continues on next lines + +If a function has a variable number of arguments, its description should +be written in kernel-doc notation as:: + + * @...: description + +Function context +~~~~~~~~~~~~~~~~ + +The context in which a function can be called should be described in a +section named ``Context``. This should include whether the function +sleeps or can be called from interrupt context, as well as what locks +it takes, releases and expects to be held by its caller. + +Examples:: + + * Context: Any context. + * Context: Any context. Takes and releases the RCU lock. + * Context: Any context. Expects <lock> to be held by caller. + * Context: Process context. May sleep if @gfp flags permit. + * Context: Process context. Takes and releases <mutex>. + * Context: Softirq or process context. Takes and releases <lock>, BH-safe. + * Context: Interrupt context. + +Return values +~~~~~~~~~~~~~ + +The return value, if any, should be described in a dedicated section +named ``Return``. + +.. note:: + + #) The multi-line descriptive text you provide does *not* recognize + line breaks, so if you try to format some text nicely, as in:: + + * Return: + * 0 - OK + * -EINVAL - invalid argument + * -ENOMEM - out of memory + + this will all run together and produce:: + + Return: 0 - OK -EINVAL - invalid argument -ENOMEM - out of memory + + So, in order to produce the desired line breaks, you need to use a + ReST list, e. g.:: + + * Return: + * * 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 + as a new section heading, which probably won't produce the desired + effect. + +Structure, union, and enumeration documentation +----------------------------------------------- + +The general format of a struct, union, and enum kernel-doc comment is:: + + /** + * struct struct_name - Brief description. + * @member1: Description of member1. + * @member2: Description of member2. + * One can provide multiple line descriptions + * for members. + * + * Description of the structure. + */ + +You can replace the ``struct`` in the above example with ``union`` or +``enum`` to describe unions or enums. ``member`` is used to mean struct +and union member names 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. + +Members +~~~~~~~ + +Members of structs, unions and enums should be documented the same way +as function parameters; they immediately succeed the short description +and may be multi-line. + +Inside a struct or union 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 + * @d: fourth member + * + * Longer description + */ + struct my_struct { + int a; + int b; + /* private: internal use only */ + int c; + /* public: the next one is public */ + int d; + }; + +Nested structs/unions +~~~~~~~~~~~~~~~~~~~~~ + +It is possible to document nested structs and unions, like:: + + /** + * struct nested_foobar - a struct with nested unions and structs + * @memb1: first member of anonymous union/anonymous struct + * @memb2: second member of anonymous union/anonymous struct + * @memb3: third member of anonymous union/anonymous struct + * @memb4: fourth member of anonymous union/anonymous struct + * @bar: non-anonymous union + * @bar.st1: struct st1 inside @bar + * @bar.st2: struct st2 inside @bar + * @bar.st1.memb1: first member of struct st1 on union bar + * @bar.st1.memb2: second member of struct st1 on union bar + * @bar.st2.memb1: first member of struct st2 on union bar + * @bar.st2.memb2: second member of struct st2 on union bar + */ + struct nested_foobar { + /* Anonymous union/struct*/ + union { + struct { + int memb1; + int memb2; + } + struct { + void *memb3; + int memb4; + } + } + union { + struct { + int memb1; + int memb2; + } st1; + struct { + void *memb1; + int memb2; + } st2; + } bar; + }; + +.. note:: + + #) When documenting nested structs or unions, if the struct/union ``foo`` + is named, the member ``bar`` inside it should be documented as + ``@foo.bar:`` + #) When the nested struct/union is anonymous, the member ``bar`` in it + should be documented as ``@bar:`` + +In-line member documentation comments +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +The structure members may also be documented in-line within the definition. +There are two styles, single-line comments where both the opening ``/**`` and +closing ``*/`` are on the same line, and multi-line comments where they are each +on a line of their own, like all other kernel-doc comments:: + + /** + * 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; + union { + /** @foobar: Single line description. */ + int foobar; + }; + /** @bar2: Description for struct @bar2 inside @foo */ + struct { + /** + * @bar2.barbar: Description for @barbar inside @foo.bar2 + */ + int barbar; + } bar2; + }; + +Typedef documentation +--------------------- + +The general format of a typedef kernel-doc comment is:: + + /** + * typedef type_name - Brief description. + * + * Description of the type. + */ + +Typedefs with function prototypes can also be documented:: + + /** + * typedef type_name - Brief description. + * @arg1: description of arg1 + * @arg2: description of arg2 + * + * Description of the type. + * + * Context: Locking context. + * Return: Meaning of the return value. + */ + typedef void (*type_name)(struct v4l2_ctrl *arg1, void *arg2); + +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.) + +````literal```` + A literal block that should be handled as-is. The output will use a + ``monospaced font``. + + Useful if you need to use special characters that would otherwise have some + meaning either by kernel-doc script or by reStructuredText. + + This is particularly useful if you need to use things like ``%ph`` inside + a function description. + +``$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 +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +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:: + + See foo(). + See struct foo. + See union bar. + See enum baz. + See typedef meh. + +However, if you want custom text in the cross-reference link, that can be done +through the following syntax:: + + 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. + +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. + +Including kernel-doc comments +============================= + +The documentation comments may be included in 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: + +identifiers: *[ function/type ...]* + Include documentation for each *function* and *type* in *source*. + If no *function* is specified, the documentation for all functions + and types in the *source* will be included. + + Examples:: + + .. kernel-doc:: lib/bitmap.c + :identifiers: bitmap_parselist bitmap_parselist_user + + .. 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. + +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 + +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/kerneldoc.py``. Internally, it uses the +``scripts/kernel-doc`` script to extract the documentation comments from the +source. + +.. _kernel_doc: + +How to use kernel-doc to generate man pages +------------------------------------------- + +If you just want to use kernel-doc to generate man pages you can do this +from the kernel git tree:: + + $ scripts/kernel-doc -man \ + $(git grep -l '/\*\*' -- :^Documentation :^tools) \ + | scripts/split-man.pl /tmp/man + +Some older versions of git do not support some of the variants of syntax for +path exclusion. One of the following commands may work for those versions:: + + $ scripts/kernel-doc -man \ + $(git grep -l '/\*\*' -- . ':!Documentation' ':!tools') \ + | scripts/split-man.pl /tmp/man + + $ scripts/kernel-doc -man \ + $(git grep -l '/\*\*' -- . ":(exclude)Documentation" ":(exclude)tools") \ + | scripts/split-man.pl /tmp/man diff --git a/Documentation/doc-guide/maintainer-profile.rst b/Documentation/doc-guide/maintainer-profile.rst new file mode 100644 index 000000000..755d39f0d --- /dev/null +++ b/Documentation/doc-guide/maintainer-profile.rst @@ -0,0 +1,45 @@ +.. 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. + +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 new file mode 100644 index 000000000..5da0046f7 --- /dev/null +++ b/Documentation/doc-guide/parse-headers.rst @@ -0,0 +1,192 @@ +=========================== +Including uAPI header files +=========================== + +Sometimes, it is useful to include header files and C example codes in +order to describe the userspace API and to generate cross-references +between the code and the documentation. Adding cross-references for +userspace API files has an additional vantage: Sphinx will generate warnings +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/userspace-api/media/Makefile`` for an example +about how to use it inside the Kernel tree. + +.. _parse_headers: + +parse_headers.pl +^^^^^^^^^^^^^^^^ + +NAME +**** + + +parse_headers.pl - parse a C file, in order to identify functions, structs, +enums and defines and create cross-references to a Sphinx book. + + +SYNOPSIS +******** + + +\ **parse_headers.pl**\ [<options>] <C_FILE> <OUT_FILE> [<EXCEPTIONS_FILE>] + +Where <options> can be: --debug, --help or --usage. + + +OPTIONS +******* + + + +\ **--debug**\ + + Put the script in verbose mode, useful for debugging. + + + +\ **--usage**\ + + Prints a brief help message and exits. + + + +\ **--help**\ + + Prints a more detailed help message and exits. + + +DESCRIPTION +*********** + + +Convert a C header or source file (C_FILE), into a ReStructured Text +included via ..parsed-literal block with cross-references for the +documentation files that describe the API. It accepts an optional +EXCEPTIONS_FILE with describes what elements will be either ignored or +be pointed to a non-default reference. + +The output is written at the (OUT_FILE). + +It is capable of identifying defines, functions, structs, typedefs, +enums and enum symbols and create cross-references for all of them. +It is also capable of distinguish #define used for specifying a Linux +ioctl. + +The EXCEPTIONS_FILE contain two types of statements: \ **ignore**\ or \ **replace**\ . + +The syntax for the ignore tag is: + + +ignore \ **type**\ \ **name**\ + +The \ **ignore**\ means that it won't generate cross references for a +\ **name**\ symbol of type \ **type**\ . + +The syntax for the replace tag is: + + +replace \ **type**\ \ **name**\ \ **new_value**\ + +The \ **replace**\ means that it will generate cross references for a +\ **name**\ symbol of type \ **type**\ , but, instead of using the default +replacement rule, it will use \ **new_value**\ . + +For both statements, \ **type**\ can be either one of the following: + + +\ **ioctl**\ + + The ignore or replace statement will apply to ioctl definitions like: + + #define VIDIOC_DBG_S_REGISTER _IOW('V', 79, struct v4l2_dbg_register) + + + +\ **define**\ + + The ignore or replace statement will apply to any other #define found + at C_FILE. + + + +\ **typedef**\ + + The ignore or replace statement will apply to typedef statements at C_FILE. + + + +\ **struct**\ + + The ignore or replace statement will apply to the name of struct statements + at C_FILE. + + + +\ **enum**\ + + The ignore or replace statement will apply to the name of enum statements + at C_FILE. + + + +\ **symbol**\ + + The ignore or replace statement will apply to the name of enum value + at C_FILE. + + For replace statements, \ **new_value**\ will automatically use :c:type: + references for \ **typedef**\ , \ **enum**\ and \ **struct**\ types. It will use :ref: + for \ **ioctl**\ , \ **define**\ and \ **symbol**\ types. The type of reference can + also be explicitly defined at the replace statement. + + + +EXAMPLES +******** + + +ignore define _VIDEODEV2_H + + +Ignore a #define _VIDEODEV2_H at the C_FILE. + +ignore symbol PRIVATE + + +On a struct like: + +enum foo { BAR1, BAR2, PRIVATE }; + +It won't generate cross-references for \ **PRIVATE**\ . + +replace symbol BAR1 :c:type:\`foo\` +replace symbol BAR2 :c:type:\`foo\` + + +On a struct like: + +enum foo { BAR1, BAR2, PRIVATE }; + +It will make the BAR1 and BAR2 enum symbols to cross reference the foo +symbol at the C domain. + + +BUGS +**** + + +Report bugs to Mauro Carvalho Chehab <mchehab@kernel.org> + + +COPYRIGHT +********* + + +Copyright (c) 2016 by Mauro Carvalho Chehab <mchehab+samsung@kernel.org>. + +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 new file mode 100644 index 000000000..896478baf --- /dev/null +++ b/Documentation/doc-guide/sphinx.rst @@ -0,0 +1,449 @@ +.. _sphinxdoc: + +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. + +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_install: + +Sphinx Install +============== + +The ReST markups currently used by the Documentation/ files are meant to be +built with ``Sphinx`` version 1.3 or higher. + +There's a script that checks for the Sphinx requirements. Please see +:ref:`sphinx-pre-install` for further details. + +Most distributions are shipped with Sphinx, but its toolchain is fragile, +and it is not uncommon that upgrading it or some other Python packages +on your machine would cause the documentation build to break. + +A way to avoid that is to use a different version than the one shipped +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 in separate, + 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:: + + $ 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, +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. + +Image output +------------ + +The kernel documentation build system contains an extension that +handles images on 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 +still build the documentation, but won't include any images at the +output. + +PDF and LaTeX builds +-------------------- + +Such builds are currently supported only with Sphinx versions 1.4 and higher. + +For PDF and LaTeX output, you'll also need ``XeLaTeX`` version 3.14159265. + +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. + +.. _sphinx-pre-install: + +Checking for Sphinx dependencies +-------------------------------- + +There's a script that automatically check 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 + 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 + pip install -r Documentation/sphinx/requirements.txt + + Can't build as 1 mandatory dependency is missing at ./scripts/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 +that a virtual Python environment will be used. The ones needed for html +builds are assumed to be mandatory; the others to be optional. + +It supports two optional parameters: + +``--no-pdf`` + Disable checks for PDF; + +``--no-virtualenv`` + Use OS packaging for Sphinx instead of Python virtual environment. + + +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 you'll also need +``XeLaTeX`` and ``convert(1)`` from ImageMagick (https://www.imagemagick.org). +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. For the most part the documentation should be plain text with + just enough consistency in formatting that it can be converted to + other formats. + +* Please keep the formatting changes minimal when converting existing + documentation to reStructuredText. + +* Also update the content, not just the formatting, when converting + documentation. + +* 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. + +* For inserting fixed width text blocks (for code examples, use case + examples, etc.), use ``::`` for anything that doesn't really benefit + from syntax highlighting, especially short snippets. Use + ``.. code-block:: <language>`` for longer code blocks that benefit + from highlighting. For a short snippet of code embedded in the text, use \`\`. + + +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``. + +Please note that there is no need to use ``c:func:`` to generate cross +references to function documentation. Due to some Sphinx extension magic, +the documentation build system will automatically turn a reference to +``function()`` into a cross reference if an index entry for the given +function name exists. If you see ``c:func:`` use in a kernel document, +please feel free to remove it. + + +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 + +Cross-referencing +----------------- + +Cross-referencing from one documentation page to another can be done by passing +the path to the file starting from the Documentation folder. +For example, to cross-reference to this page (the .rst extension is optional):: + + See Documentation/doc-guide/sphinx.rst. + +If you want to use a relative path, you need to use Sphinx's ``doc`` directive. +For example, referencing this page from the same directory would be done as:: + + See :doc:`sphinx`. + +For information on cross-referencing to kernel-doc functions or types, see +Documentation/doc-guide/kernel-doc.rst. + +.. _sphinx_kfigure: + +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`):: + + .. kernel-figure:: svg_image.svg + :alt: simple SVG image + + SVG image example + +.. _svg_image_example: + +.. kernel-figure:: svg_image.svg + :alt: simple SVG image + + SVG image example + +The kernel figure (and image) directive support **DOT** formated files, see + +* DOT: http://graphviz.org/pdf/dotguide.pdf +* Graphviz: http://www.graphviz.org/content/dot-language + +A simple example (:ref:`hello_dot_file`):: + + .. kernel-figure:: hello.dot + :alt: hello world + + DOT's hello world example + +.. _hello_dot_file: + +.. kernel-figure:: hello.dot + :alt: hello world + + DOT's hello world example + +Embed *render* markups (or languages) like Graphviz's **DOT** is provided by the +``kernel-render`` directives.:: + + .. kernel-render:: DOT + :alt: foobar digraph + :caption: Embedded **DOT** (Graphviz) code + + digraph foo { + "bar" -> "baz"; + } + +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 +*literal-block* (:ref:`hello_dot_render`). + +.. _hello_dot_render: + +.. kernel-render:: DOT + :alt: foobar digraph + :caption: Embedded **DOT** (Graphviz) code + + digraph foo { + "bar" -> "baz"; + } + +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`). + +Embedded **SVG**:: + + .. kernel-render:: SVG + :caption: Embedded **SVG** markup + :alt: so-nw-arrow + + <?xml version="1.0" encoding="UTF-8"?> + <svg xmlns="http://www.w3.org/2000/svg" version="1.1" ...> + ... + </svg> + +.. _hello_svg_render: + +.. kernel-render:: SVG + :caption: Embedded **SVG** markup + :alt: so-nw-arrow + + <?xml version="1.0" encoding="UTF-8"?> + <svg xmlns="http://www.w3.org/2000/svg" + version="1.1" baseProfile="full" width="70px" height="40px" viewBox="0 0 700 400"> + <line x1="180" y1="370" x2="500" y2="50" stroke="black" stroke-width="15px"/> + <polygon points="585 0 525 25 585 50" transform="rotate(135 525 25)"/> + </svg> diff --git a/Documentation/doc-guide/svg_image.svg b/Documentation/doc-guide/svg_image.svg new file mode 100644 index 000000000..5405f85b8 --- /dev/null +++ b/Documentation/doc-guide/svg_image.svg @@ -0,0 +1,10 @@ +<?xml version="1.0" encoding="UTF-8"?> +<!-- originate: https://commons.wikimedia.org/wiki/File:Variable_Resistor.svg --> +<svg xmlns="http://www.w3.org/2000/svg" + version="1.1" baseProfile="full" + width="70px" height="40px" viewBox="0 0 700 400"> + <line x1="0" y1="200" x2="700" y2="200" stroke="black" stroke-width="20px"/> + <rect x="100" y="100" width="500" height="200" fill="white" stroke="black" stroke-width="20px"/> + <line x1="180" y1="370" x2="500" y2="50" stroke="black" stroke-width="15px"/> + <polygon points="585 0 525 25 585 50" transform="rotate(135 525 25)"/> +</svg> |
