Kconfiglib

A Python library for doing stuff with Kconfig-based configuration systems. Can extract information, query and set symbol values, and read and write .config files. Highly compatible with the scripts/kconfig/*conf utilities in the kernel, usually invoked via make targets such as menuconfig and defconfig.

Supports both Python 2 and Python 3 without modification.

One feature is missing: Kconfiglib assumes the modules symbol is MODULES, and will warn if option modules is set on some other symbol. Let me know if this is a problem for you, as adding support shouldn't be that hard. I haven't seen modules used outside the kernel, where the name is unlikely to change.

Installation

Installation instructions for the Linux kernel

Run the following commands in the kernel root:

$ git clone git://github.com/ulfalizer/Kconfiglib.git  
$ git am Kconfiglib/makefile.patch

(Note: The directory name Kconfiglib/ is significant.)

In addition to creating a handy interface, the make targets created by the patch (scriptconfig and iscriptconfig) are needed to pick up environment variables set in the kernel makefiles and later referenced in the Kconfig files (ARCH, SRCARCH, and KERNELVERSION as of Linux v4.0-rc3). The documentation explains how the make targets are used. The compatibility tests in the test suite also needs them.

Please tell me if the patch does not apply. It should be trivial to apply manually, as it's just a block of text that needs to be inserted near the other *conf: targets.

Installation instructions for other projects

The entire library is contained in kconfiglib.py. Drop it somewhere and read the documentation. Make sure Kconfiglib sees environment variables referenced in the configuration.

You can also use pip to install.

pip install https://github.com/ulfalizer/Kconfiglib/tarball/master

Documentation

The (extensive) documentation is generated by running

$ pydoc kconfiglib

in the Kconfiglib/ directory. For HTML output, use

$ pydoc -w kconfiglib

You could also browse the docstrings directly in kconfiglib.py.

Please tell me if something is unclear to you or can be explained better. The Kconfig language has some dark corners.

Examples

• The examples/ directory contains simple example scripts. See the documentation for how to run them.

• gen-manual-lists.py from Buildroot generates listings for the appendix of the manual.

• genboardscfg.py from Das U-Boot generates some sort of legacy board database by pulling information from a newly added Kconfig-based configuration system (as far as I understand it :).

• SConf builds an interactive configuration interface (like menuconfig, etc.) on top of Kconfiglib, for use e.g. with SCons.

• kconfig-diff.py -- a script by dubiousjim that compares kernel configurations.

• Originally, Kconfiglib was used in chapter 4 of my master's thesis to automatically generate a "minimal" kernel for a given system. Parts of it bother me a bit now, but that's how it goes with old work.

Test suite

The test suite is run with

$ python(3) Kconfiglib/testsuite.py

It must be run from the top-level kernel directory.

NOTE: Some tests currently overwrite .config in the kernel root, so make sure to back it up.

The test suite consists of a set of selftests and a set of compatibility tests that compare (character for character) configurations generated by Kconfiglib with configurations generated by scripts/kconfig/conf for a number of cases. You might want to use the "speedy" option; see testsuite.py.

Kconfiglib is much faster than the test suite would indicate. Most of the time is spent waiting around for make or the C utilities. Adding some multiprocessing to the test suite would make sense.

Misc. notes

• Please tell me if you miss some API. It might be possible to extract some useful information from internal data structures (the expression format is pretty easy to understand for example), but having an API is obviously cleaner and safer.

  Pull requests are welcome too. Don't worry about getting everything right and adding test cases -- I could fix things up. I know Kconfig has a lot of tricky corners.

• Using __slots__ on classes would speed things up a bit and save memory. (genboardscfg.py went from 1.6 to 1.4 seconds on my system for example.) It'd remove some flexibility though.

• Kconfiglib works well with PyPy. It might give a nice speedup over CPython when batch processing a large number of configurations, as well as when running the test suite.

• At least two things make it a bit awkward to replicate a 'menuconfig'-like interface in Kconfiglib at the moment (but see SConf, as mentioned above). APIs could be added if needed.

  • There are no good APIs for figuring out what other symbols change in value when the value of some symbol is changed, to allow for "live" updates in the configuration interface. The simplest workaround is to refetch the value of each currently visible symbol every time a symbol value is changed.

  • 'menuconfig' sometimes creates menus implicitly by looking at dependencies. For example, a list of symbols where all symbols depend on the first symbol might create such a menu rooted at the first symbol. Recreating such "cosmetic" menus might be awkward.

    (There is already basic support internally though, because it's needed to get obscure choice behavior right -- see _determine_actual_symbols() and its helper _has_auto_menu_dep_on().)

• fpemud has put together Python bindings to internal functions in the C implementation. This is an alternative to Kconfiglib's all-Python approach.

• The test suite failures (should be the only ones) for the following Blackfin defconfigs on e.g. Linux 3.7.0-rc8 are due to a bug in the C implementation:

  • arch/blackfin/configs/CM-BF537U_defconfig
  • arch/blackfin/configs/BF548-EZKIT_defconfig
  • arch/blackfin/configs/BF527-EZKIT_defconfig
  • arch/blackfin/configs/BF527-EZKIT-V2_defconfig
  • arch/blackfin/configs/TCM-BF537_defconfig

Thanks

Thanks to Philip Craig for adding support for the allnoconfig_y option and fixing an obscure issue with comments inside choices (that didn't affect correctness but made outputs differ). allnoconfig_y is used to force certain symbols to y during make allnoconfig to improve coverage.

License (ISC)

Copyright (c) 2011-2016, Ulf Magnusson [email protected]

Permission to use, copy, modify, and/or distribute this software for any purpose with or without fee is hereby granted, provided that the above copyright notice and this permission notice appear in all copies.

THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.