Commit 0842b245 authored by Paul Jackson's avatar Paul Jackson Committed by Linus Torvalds

doc: document the kernel-doc conventions for kernel hackers

Provide documentation of the kernel-doc documentation conventions oriented
to kernel hackers.

Since I figure that there will be more people reading this
kernel-doc-nano-HOWTO.txt file who are kernel developers focused on the
rest of the kernel, than there will be readers of this file who are
documentation developers extracting that embedded kernel-doc
documentation, I have taken the liberty of making the new section added

  How to format kernel-doc comments

the first section of the kernel-doc-nano-HOWTO.txt file.

This first section is intended to introduce, motivate and provide basic
usage of the kernel-doc mechanism for kernel hackers developing other
portions of the kernel.
Signed-off-by: default avatarPaul Jackson <>
Acked-by: default avatarRandy Dunlap <>
Cc: Alan Cox <>
Signed-off-by: default avatarAndrew Morton <>
Signed-off-by: default avatarLinus Torvalds <>
parent 659179b2
kernel-doc nano-HOWTO
How to format kernel-doc comments
In order to provide embedded, 'C' friendly, easy to maintain,
but consistent and extractable documentation of the functions and
data structures in the Linux kernel, the Linux kernel has adopted
a consistent style for documenting functions and their parameters,
and structures and their members.
The format for this documentation is called the kernel-doc format.
It is documented in this Documentation/kernel-doc-nano-HOWTO.txt file.
This style embeds the documentation within the source files, using
a few simple conventions. The scripts/kernel-doc perl script, some
SGML templates in Documentation/DocBook, and other tools understand
these conventions, and are used to extract this embedded documentation
into various documents.
In order to provide good documentation of kernel functions and data
structures, please use the following conventions to format your
kernel-doc comments in Linux kernel source.
We definitely need kernel-doc formatted documentation for functions
that are exported to loadable modules using EXPORT_SYMBOL.
We also look to provide kernel-doc formatted documentation for
functions externally visible to other kernel files (not marked
We also recommend providing kernel-doc formatted documentation
for private (file "static") routines, for consistency of kernel
source code layout. But this is lower priority and at the
discretion of the MAINTAINER of that kernel source file.
Data structures visible in kernel include files should also be
documented using kernel-doc formatted comments.
The opening comment mark "/**" is reserved for kernel-doc comments.
Only comments so marked will be considered by the kernel-doc scripts,
and any comment so marked must be in kernel-doc format. Do not use
"/**" to be begin a comment block unless the comment block contains
kernel-doc formatted comments. The closing comment marker for
kernel-doc comments can be either "*/" or "**/".
Kernel-doc comments should be placed just before the function
or data structure being described.
Example kernel-doc function comment:
* foobar() - short function description of foobar
* @arg1: Describe the first argument to foobar.
* @arg2: Describe the second argument to foobar.
* One can provide multiple line descriptions
* for arguments.
* A longer description, with more discussion of the function foobar()
* that might be useful to those using or modifying it. Begins with
* empty comment line, and may include additional embedded empty
* comment lines.
* The longer description can have multiple paragraphs.
The first line, with the short description, must be on a single line.
The @argument descriptions must begin on the very next line following
this opening short function description line, with no intervening
empty comment lines.
Example kernel-doc data structure comment.
* struct blah - the basic blah structure
* @mem1: describe the first member of struct blah
* @mem2: describe the second member of struct blah,
* perhaps with more lines and words.
* Longer description of this structure.
The kernel-doc function comments describe each parameter to the
function, in order, with the @name lines.
The kernel-doc data structure comments describe each structure member
in the data structure, with the @name lines.
The longer description formatting is "reflowed", losing your line
breaks. So presenting carefully formatted lists within these
descriptions won't work so well; derived documentation will lose
the formatting.
See the section below "How to add extractable documentation to your
source files" for more details and notes on how to format kernel-doc
Components of the kernel-doc system
Many places in the source tree have extractable documentation in the
form of block comments above functions. The components of this system
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