blob: d52fbfd9ca7dc1b87e0137a2d457b12af9dd73c4 [file] [log] [blame]
.. _kconfig_extensions:
Kconfig extensions
Zephyr uses the `Kconfiglib <>`__
implementation of `Kconfig
which includes some Kconfig extensions:
- Environment variables in ``source`` statements are expanded directly, meaning
no "bounce" symbols with ``option env="ENV_VAR"`` need to be defined.
.. note::
``option env`` has been removed from the C tools as of Linux 4.18 as well.
The recommended syntax for referencing environment variables is ``$(FOO)``
rather than ``$FOO``. This uses the new `Kconfig preprocessor
The ``$FOO`` syntax for expanding environment variables is only supported for
backwards compatibility.
- The ``source`` statement supports glob patterns and includes each matching
file. A pattern is required to match at least one file.
Consider the following example:
.. code-block:: none
source "foo/bar/*/Kconfig"
If the pattern ``foo/bar/*/Kconfig`` matches the files
:file:`foo/bar/baz/Kconfig` and :file:`foo/bar/qaz/Kconfig`, the statement
above is equivalent to the following two ``source`` statements:
.. code-block:: none
source "foo/bar/baz/Kconfig"
source "foo/bar/qaz/Kconfig"
If no files match the pattern, an error is generated.
The wildcard patterns accepted are the same as for the Python `glob
<>`__ module.
For cases where it's okay for a pattern to match no files (or for a plain
filename to not exist), a separate ``osource`` (*optional source*) statement
is available. ``osource`` is a no-op if no file matches.
.. note::
``source`` and ``osource`` are analogous to ``include`` and
``-include`` in Make.
- An ``rsource`` statement is available for including files specified with a
relative path. The path is relative to the directory of the :file:`Kconfig`
file that contains the ``rsource`` statement.
As an example, assume that :file:`foo/Kconfig` is the top-level
:file:`Kconfig` file, and that :file:`foo/bar/Kconfig` has the following
.. code-block:: none
source "qaz/Kconfig1"
rsource "qaz/Kconfig2"
This will include the two files :file:`foo/qaz/Kconfig1` and
``rsource`` can be used to create :file:`Kconfig` "subtrees" that can be
moved around freely.
``rsource`` also supports glob patterns.
A drawback of ``rsource`` is that it can make it harder to figure out where a
file gets included, so only use it if you need it.
- An ``orsource`` statement is available that combines ``osource`` and
For example, the following statement will include :file:`Kconfig1` and
:file:`Kconfig2` from the current directory (if they exist):
.. code-block:: none
orsource "Kconfig[12]"
- ``def_int``, ``def_hex``, and ``def_string`` keywords are available,
analogous to ``def_bool``. These set the type and add a ``default`` at the
same time.