diff options
| -rw-r--r-- | README.rst | 20 |
1 files changed, 13 insertions, 7 deletions
@@ -28,9 +28,10 @@ Kconfiglib implements the recently added `Kconfig preprocessor <https://github.com/torvalds/linux/blob/master/Documentation/kbuild/kconfig-macro-language.txt>`_. For backwards compatibility, environment variables can be referenced both as ``$(FOO)`` (the new syntax) and as ``$FOO`` (the old syntax). The old syntax is -deprecated, but will probably be supported for a very long time (the major -version would be increased if support is ever dropped). Using the old syntax -with an undefined environment variable keeps the string as is. +deprecated, but will probably be supported for a long time, as its needed to +stay compatible with older Linux kernels. The major version will be increased +if support is ever dropped. Using the old syntax with an undefined environment +variable keeps the string as is. Note: See `this issue <https://github.com/ulfalizer/Kconfiglib/issues/47>`_ if you run into a "macro expanded to blank string" error with kernel 4.18+. @@ -371,10 +372,15 @@ The following Kconfig extensions are available: This is the standard behavior with the new `Kconfig preprocessor <https://github.com/torvalds/linux/blob/master/Documentation/kbuild/kconfig-macro-language.txt>`_, which Kconfiglib implements. - - ``option env`` symbols are supported for backwards compatibility, with the - caveat that they must have the same name as the environment variables they - reference. A warning is printed if the names differ. + + ``option env`` symbols are accepted but ignored, which leads the caveat that + they must have the same name as the environment variables they reference + (Kconfiglib warns if the names differ). This keeps Kconfiglib compatible with + older Linux kernels, where the name of the ``option env`` symbol always + matched the environment variable. Compatibility with older Linux kernels is + the main reason ``option env`` is still supported. + + The C tools have dropped support for ``option env``. - Two extra optional warnings can be enabled by setting environment variables, covering cases that are easily missed when making changes to Kconfig files: |