docs: get rid of kernel-doc-nano-HOWTO.txt
Everything there is already described at Documentation/doc-guide/kernel-doc.rst. So, there's no reason why to keep it anymore. Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com> Signed-off-by: Jonathan Corbet <corbet@lwn.net>
This commit is contained in:
Mauro Carvalho Chehab
Jonathan Corbet
parent
93626d7a76
commit
857af3b775
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@ -228,8 +228,6 @@ isdn/
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- directory with info on the Linux ISDN support, and supported cards.
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kbuild/
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- directory with info about the kernel build process.
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kernel-doc-nano-HOWTO.txt
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- outdated info about kernel-doc documentation.
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kdump/
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- directory with mini HowTo on getting the crash dump code to work.
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doc-guide/
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@ -1,322 +0,0 @@
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NOTE: this document is outdated and will eventually be removed. See
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Documentation/doc-guide/ for current information.
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kernel-doc nano-HOWTO
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=====================
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How to format kernel-doc comments
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---------------------------------
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In order to provide embedded, 'C' friendly, easy to maintain,
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but consistent and extractable documentation of the functions and
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data structures in the Linux kernel, the Linux kernel has adopted
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a consistent style for documenting functions and their parameters,
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and structures and their members.
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The format for this documentation is called the kernel-doc format.
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It is documented in this Documentation/kernel-doc-nano-HOWTO.txt file.
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This style embeds the documentation within the source files, using
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a few simple conventions. The scripts/kernel-doc perl script, the
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Documentation/sphinx/kerneldoc.py Sphinx extension and other tools understand
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these conventions, and are used to extract this embedded documentation
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into various documents.
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In order to provide good documentation of kernel functions and data
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structures, please use the following conventions to format your
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kernel-doc comments in Linux kernel source.
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We definitely need kernel-doc formatted documentation for functions
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that are exported to loadable modules using EXPORT_SYMBOL.
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We also look to provide kernel-doc formatted documentation for
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functions externally visible to other kernel files (not marked
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"static").
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We also recommend providing kernel-doc formatted documentation
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for private (file "static") routines, for consistency of kernel
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source code layout. But this is lower priority and at the
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discretion of the MAINTAINER of that kernel source file.
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Data structures visible in kernel include files should also be
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documented using kernel-doc formatted comments.
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The opening comment mark "/**" is reserved for kernel-doc comments.
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Only comments so marked will be considered by the kernel-doc scripts,
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and any comment so marked must be in kernel-doc format. Do not use
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"/**" to be begin a comment block unless the comment block contains
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kernel-doc formatted comments. The closing comment marker for
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kernel-doc comments can be either "*/" or "**/", but "*/" is
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preferred in the Linux kernel tree.
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Kernel-doc comments should be placed just before the function
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or data structure being described.
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Example kernel-doc function comment:
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/**
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* foobar() - short function description of foobar
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* @arg1: Describe the first argument to foobar.
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* @arg2: Describe the second argument to foobar.
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* One can provide multiple line descriptions
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* for arguments.
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*
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* A longer description, with more discussion of the function foobar()
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* that might be useful to those using or modifying it. Begins with
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* empty comment line, and may include additional embedded empty
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* comment lines.
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*
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* The longer description can have multiple paragraphs.
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*
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* Return: Describe the return value of foobar.
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*/
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The short description following the subject can span multiple lines
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and ends with an @argument description, an empty line or the end of
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the comment block.
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The @argument descriptions must begin on the very next line following
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this opening short function description line, with no intervening
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empty comment lines.
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If a function parameter is "..." (varargs), it should be listed in
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kernel-doc notation as:
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* @...: description
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The return value, if any, should be described in a dedicated section
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named "Return".
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Example kernel-doc data structure comment.
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/**
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* struct blah - the basic blah structure
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* @mem1: describe the first member of struct blah
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* @mem2: describe the second member of struct blah,
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* perhaps with more lines and words.
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*
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* Longer description of this structure.
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*/
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The kernel-doc function comments describe each parameter to the
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function, in order, with the @name lines.
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The kernel-doc data structure comments describe each structure member
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in the data structure, with the @name lines.
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The longer description formatting is "reflowed", losing your line
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breaks. So presenting carefully formatted lists within these
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descriptions won't work so well; derived documentation will lose
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the formatting.
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See the section below "How to add extractable documentation to your
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source files" for more details and notes on how to format kernel-doc
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comments.
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Components of the kernel-doc system
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-----------------------------------
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Many places in the source tree have extractable documentation in the
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form of block comments above functions. The components of this system
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are:
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- scripts/kernel-doc
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This is a perl script that hunts for the block comments and can mark
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them up directly into DocBook, ReST, man, text, and HTML. (No, not
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texinfo.)
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- scripts/docproc.c
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This is a program for converting SGML template files into SGML
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files. When a file is referenced it is searched for symbols
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exported (EXPORT_SYMBOL), to be able to distinguish between internal
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and external functions.
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It invokes kernel-doc, giving it the list of functions that
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are to be documented.
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Additionally it is used to scan the SGML template files to locate
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all the files referenced herein. This is used to generate dependency
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information as used by make.
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- Makefile
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The targets 'xmldocs', 'latexdocs', 'pdfdocs', 'epubdocs'and 'htmldocs'
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are used to build XML DocBook files, LaTeX files, PDF files,
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ePub files and html files in Documentation/.
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How to extract the documentation
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--------------------------------
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If you just want to read the ready-made books on the various
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subsystems, just type 'make epubdocs', or 'make pdfdocs', or 'make htmldocs',
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depending on your preference. If you would rather read a different format,
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you can type 'make xmldocs' and then use DocBook tools to convert
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Documentation/output/*.xml to a format of your choice (for example,
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'db2html ...' if 'make htmldocs' was not defined).
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If you want to see man pages instead, you can do this:
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$ cd linux
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$ scripts/kernel-doc -man $(find -name '*.c') | split-man.pl /tmp/man
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$ scripts/kernel-doc -man $(find -name '*.h') | split-man.pl /tmp/man
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Here is split-man.pl:
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-->
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#!/usr/bin/perl
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if ($#ARGV < 0) {
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die "where do I put the results?\n";
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}
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mkdir $ARGV[0],0777;
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$state = 0;
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while (<STDIN>) {
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if (/^\.TH \"[^\"]*\" 9 \"([^\"]*)\"/) {
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if ($state == 1) { close OUT }
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$state = 1;
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$fn = "$ARGV[0]/$1.9";
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print STDERR "Creating $fn\n";
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open OUT, ">$fn" or die "can't open $fn: $!\n";
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print OUT $_;
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} elsif ($state != 0) {
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print OUT $_;
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}
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}
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close OUT;
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<--
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If you just want to view the documentation for one function in one
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file, you can do this:
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$ scripts/kernel-doc -man -function fn file | nroff -man | less
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or this:
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$ scripts/kernel-doc -text -function fn file
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How to add extractable documentation to your source files
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---------------------------------------------------------
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The format of the block comment is like this:
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/**
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* function_name(:)? (- short description)?
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(* @parameterx(space)*: (description of parameter x)?)*
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(* a blank line)?
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* (Description:)? (Description of function)?
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* (section header: (section description)? )*
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(*)?*/
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All "description" text can span multiple lines, although the
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function_name & its short description are traditionally on a single line.
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Description text may also contain blank lines (i.e., lines that contain
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only a "*").
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"section header:" names must be unique per function (or struct,
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union, typedef, enum).
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Use the section header "Return" for sections describing the return value
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of a function.
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Avoid putting a spurious blank line after the function name, or else the
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description will be repeated!
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All descriptive text is further processed, scanning for the following special
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patterns, which are highlighted appropriately.
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'funcname()' - function
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'$ENVVAR' - environment variable
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'&struct_name' - name of a structure (up to two words including 'struct')
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'@parameter' - name of a parameter
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'%CONST' - name of a constant.
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NOTE 1: The multi-line descriptive text you provide does *not* recognize
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line breaks, so if you try to format some text nicely, as in:
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Return:
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0 - cool
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1 - invalid arg
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2 - out of memory
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this will all run together and produce:
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Return: 0 - cool 1 - invalid arg 2 - out of memory
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NOTE 2: If the descriptive text you provide has lines that begin with
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some phrase followed by a colon, each of those phrases will be taken as
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a new section heading, which means you should similarly try to avoid text
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like:
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Return:
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0: cool
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1: invalid arg
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2: out of memory
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every line of which would start a new section. Again, probably not
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what you were after.
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Take a look around the source tree for examples.
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kernel-doc for structs, unions, enums, and typedefs
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---------------------------------------------------
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Beside functions you can also write documentation for structs, unions,
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enums and typedefs. Instead of the function name you must write the name
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of the declaration; the struct/union/enum/typedef must always precede
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the name. Nesting of declarations is not supported.
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Use the argument mechanism to document members or constants.
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Inside a struct description, you can use the "private:" and "public:"
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comment tags. Structure fields that are inside a "private:" area
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are not listed in the generated output documentation. The "private:"
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and "public:" tags must begin immediately following a "/*" comment
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marker. They may optionally include comments between the ":" and the
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ending "*/" marker.
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Example:
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/**
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* struct my_struct - short description
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* @a: first member
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* @b: second member
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*
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* Longer description
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*/
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struct my_struct {
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int a;
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int b;
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/* private: internal use only */
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int c;
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};
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Including documentation blocks in source files
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----------------------------------------------
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To facilitate having source code and comments close together, you can
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include kernel-doc documentation blocks that are free-form comments
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instead of being kernel-doc for functions, structures, unions,
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enums, or typedefs. This could be used for something like a
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theory of operation for a driver or library code, for example.
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This is done by using a DOC: section keyword with a section title. E.g.:
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/**
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* DOC: Theory of Operation
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*
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* The whizbang foobar is a dilly of a gizmo. It can do whatever you
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* want it to do, at any time. It reads your mind. Here's how it works.
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*
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* foo bar splat
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*
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* The only drawback to this gizmo is that is can sometimes damage
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* hardware, software, or its subject(s).
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*/
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DOC: sections are used in ReST files.
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Tim.
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*/ <twaugh@redhat.com>
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@ -48,7 +48,7 @@ Read C language source or header FILEs, extract embedded documentation comments,
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and print formatted documentation to standard output.
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The documentation comments are identified by "/**" opening comment mark. See
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Documentation/kernel-doc-nano-HOWTO.txt for the documentation comment syntax.
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Documentation/doc-guide/kernel-doc.rst for the documentation comment syntax.
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Output format selection (mutually exclusive):
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-docbook Output DocBook format.
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