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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 parse_headers.pl 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.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 reStructuredText 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>