buildroot

// -*- mode:doc; -*-

// vim: set syntax=asciidoc:

​

== Coding style

​

Overall, these coding style rules are here to help you to add new files in

Buildroot or refactor existing ones.

​

If you slightly modify some existing file, the important thing is

to keep the consistency of the whole file, so you can:

​

* either follow the potentially deprecated coding style used in this

file,

​

* or entirely rework it in order to make it comply with these rules.

​

[[writing-rules-config-in]]

​

=== +Config.in+ file

​

+Config.in+ files contain entries for almost anything configurable in

Buildroot.

​

An entry has the following pattern:

​

---------------------

config BR2_PACKAGE_LIBFOO

    bool "libfoo"

    depends on BR2_PACKAGE_LIBBAZ

    select BR2_PACKAGE_LIBBAR

    help

      This is a comment that explains what libfoo is. The help text

      should be wrapped.

​

      http://foosoftware.org/libfoo/

---------------------

​

* The +bool+, +depends on+, +select+ and +help+ lines are indented

  with one tab.

​

* The help text itself should be indented with one tab and two

  spaces.

​

* The help text should be wrapped to fit 72 columns, where tab counts

  for 8, so 62 characters in the text itself.

​

The +Config.in+ files are the input for the configuration tool

used in Buildroot, which is the regular _Kconfig_. For further

details about the _Kconfig_ language, refer to

http://kernel.org/doc/Documentation/kbuild/kconfig-language.txt[].

​

[[writing-rules-mk]]

​

=== The +.mk+ file

​

* Header: The file starts with a header. It contains the module name,

preferably in lowercase, enclosed between separators made of 80 hashes. A

blank line is mandatory after the header:

+

---------------------

################################################################################

#

# libfoo

#

################################################################################

---------------------

+

* Assignment: use +=+ preceded and followed by one space:

+

---------------------

LIBFOO_VERSION = 1.0

LIBFOO_CONF_OPTS += --without-python-support

---------------------

+

Do not align the +=+ signs.

​

* Indentation: use tab only:

+

---------------------

define LIBFOO_REMOVE_DOC

    $(RM) -fr $(TARGET_DIR)/usr/share/libfoo/doc \

        $(TARGET_DIR)/usr/share/man/man3/libfoo*

endef

---------------------

+

Note that commands inside a +define+ block should always start with a tab,

so _make_ recognizes them as commands.

​

* Optional dependency:

​

** Prefer multi-line syntax.

+