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Linus Torvalds1da177e2005-04-16 15:20:36 -07001kernel-doc nano-HOWTO
2=====================
3
4Many places in the source tree have extractable documentation in the
5form of block comments above functions. The components of this system
6are:
7
8- scripts/kernel-doc
9
10 This is a perl script that hunts for the block comments and can mark
11 them up directly into DocBook, man, text, and HTML. (No, not
12 texinfo.)
13
14- Documentation/DocBook/*.tmpl
15
16 These are SGML template files, which are normal SGML files with
17 special place-holders for where the extracted documentation should
18 go.
19
20- scripts/docproc.c
21
22 This is a program for converting SGML template files into SGML
23 files. When a file is referenced it is searched for symbols
24 exported (EXPORT_SYMBOL), to be able to distinguish between internal
25 and external functions.
26 It invokes kernel-doc, giving it the list of functions that
27 are to be documented.
28 Additionally it is used to scan the SGML template files to locate
29 all the files referenced herein. This is used to generate dependency
30 information as used by make.
31
32- Makefile
33
34 The targets 'sgmldocs', 'psdocs', 'pdfdocs', and 'htmldocs' are used
35 to build DocBook files, PostScript files, PDF files, and html files
36 in Documentation/DocBook.
37
38- Documentation/DocBook/Makefile
39
40 This is where C files are associated with SGML templates.
41
42
43How to extract the documentation
44--------------------------------
45
46If you just want to read the ready-made books on the various
47subsystems (see Documentation/DocBook/*.tmpl), just type 'make
Randy Dunlapd28bee02006-02-01 03:06:57 -080048psdocs', or 'make pdfdocs', or 'make htmldocs', depending on your
49preference. If you would rather read a different format, you can type
50'make sgmldocs' and then use DocBook tools to convert
51Documentation/DocBook/*.sgml to a format of your choice (for example,
Linus Torvalds1da177e2005-04-16 15:20:36 -070052'db2html ...' if 'make htmldocs' was not defined).
53
54If you want to see man pages instead, you can do this:
55
56$ cd linux
57$ scripts/kernel-doc -man $(find -name '*.c') | split-man.pl /tmp/man
58$ scripts/kernel-doc -man $(find -name '*.h') | split-man.pl /tmp/man
59
60Here is split-man.pl:
61
62-->
63#!/usr/bin/perl
64
65if ($#ARGV < 0) {
66 die "where do I put the results?\n";
67}
68
69mkdir $ARGV[0],0777;
70$state = 0;
71while (<STDIN>) {
72 if (/^\.TH \"[^\"]*\" 4 \"([^\"]*)\"/) {
73 if ($state == 1) { close OUT }
74 $state = 1;
75 $fn = "$ARGV[0]/$1.4";
76 print STDERR "Creating $fn\n";
77 open OUT, ">$fn" or die "can't open $fn: $!\n";
78 print OUT $_;
79 } elsif ($state != 0) {
80 print OUT $_;
81 }
82}
83
84close OUT;
85<--
86
87If you just want to view the documentation for one function in one
88file, you can do this:
89
90$ scripts/kernel-doc -man -function fn file | nroff -man | less
91
92or this:
93
94$ scripts/kernel-doc -text -function fn file
95
96
97How to add extractable documentation to your source files
98---------------------------------------------------------
99
100The format of the block comment is like this:
101
102/**
103 * function_name(:)? (- short description)?
104(* @parameterx: (description of parameter x)?)*
105(* a blank line)?
106 * (Description:)? (Description of function)?
107 * (section header: (section description)? )*
108(*)?*/
109
110The short function description cannot be multiline, but the other
111descriptions can be (and they can contain blank lines). Avoid putting a
112spurious blank line after the function name, or else the description will
113be repeated!
114
115All descriptive text is further processed, scanning for the following special
116patterns, which are highlighted appropriately.
117
118'funcname()' - function
119'$ENVVAR' - environment variable
120'&struct_name' - name of a structure (up to two words including 'struct')
121'@parameter' - name of a parameter
122'%CONST' - name of a constant.
123
124Take a look around the source tree for examples.
125
126
Randy Dunlapd28bee02006-02-01 03:06:57 -0800127kernel-doc for structs, unions, enums, and typedefs
128---------------------------------------------------
129
130Beside functions you can also write documentation for structs, unions,
131enums and typedefs. Instead of the function name you must write the name
132of the declaration; the struct/union/enum/typedef must always precede
133the name. Nesting of declarations is not supported.
134Use the argument mechanism to document members or constants.
135
136Inside a struct description, you can use the "private:" and "public:"
137comment tags. Structure fields that are inside a "private:" area
138are not listed in the generated output documentation.
139
140Example:
141
142/**
143 * struct my_struct - short description
144 * @a: first member
145 * @b: second member
146 *
147 * Longer description
148 */
149struct my_struct {
150 int a;
151 int b;
152/* private: */
153 int c;
154};
155
156
Linus Torvalds1da177e2005-04-16 15:20:36 -0700157How to make new SGML template files
158-----------------------------------
159
160SGML template files (*.tmpl) are like normal SGML files, except that
161they can contain escape sequences where extracted documentation should
162be inserted.
163
164!E<filename> is replaced by the documentation, in <filename>, for
165functions that are exported using EXPORT_SYMBOL: the function list is
166collected from files listed in Documentation/DocBook/Makefile.
167
168!I<filename> is replaced by the documentation for functions that are
169_not_ exported using EXPORT_SYMBOL.
170
171!D<filename> is used to name additional files to search for functions
172exported using EXPORT_SYMBOL.
173
174!F<filename> <function [functions...]> is replaced by the
175documentation, in <filename>, for the functions listed.
176
177
178Tim.
179*/ <twaugh@redhat.com>