# Kconfiglib #

A Python library for doing stuff with [Kconfig](https://www.kernel.org/doc/Documentation/kbuild/kconfig-language.txt)-based
configuration systems. Can extract information, query and set symbol values,
and read and write <i>.config</i> files. Highly compatible with the
<i>scripts/kconfig/\*conf</i> utilities in the kernel, usually invoked via make
targets such as <i>menuconfig</i> and <i>defconfig</i>.

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

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

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
(<i>ARCH</i>, <i>SRCARCH</i>, and <i>KERNELVERSION</i> 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
<i>*conf:</i> targets.

### Installation instructions for other projects ###

The entire library is contained in [kconfiglib.py](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 <i>Kconfiglib/</i> directory. For HTML output,
use

    $ pydoc -w kconfiglib
    
You could also browse the docstrings directly in [kconfiglib.py](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/](examples/) directory contains simple example scripts. See the documentation for how to run them.

 * [gen-manual-lists.py](http://git.buildroot.net/buildroot/tree/support/scripts/gen-manual-lists.py) from [Buildroot](http://buildroot.uclibc.org/) generates listings for the [appendix of the manual](http://buildroot.uclibc.org/downloads/manual/manual.html#_appendix).

 * [genboardscfg.py](http://git.denx.de/?p=u-boot.git;a=blob;f=tools/genboardscfg.py;hb=HEAD) from [Das U-Boot](http://www.denx.de/wiki/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](https://github.com/CoryXie/SConf) builds an interactive configuration interface (like *menuconfig*, etc.) on top of Kconfiglib, for use e.g. with SCons.

 * [kconfig-diff.py](https://gist.github.com/dubiousjim/5638961) -- a script by [dubiousjim](https://github.com/dubiousjim) that compares kernel configurations.

 * Originally, Kconfiglib was used in chapter 4 of my [master's thesis](http://liu.diva-portal.org/smash/get/diva2:473038/FULLTEXT01.pdf) 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 <i>scripts/kconfig/conf</i> for a number of cases. You
might want to use the "speedy" option; see [testsuite.py](testsuite.py).

The test suite might fail for a few configurations for kernels older than April 2006,
when a fix was added to Kconfig that's also mirrored in Kconfiglib
(see https://github.com/ulfalizer/Kconfiglib/commit/35ea8d5f1d63bdc9f8642f5ce4445e8f7c914385).
This is harmless, and only counts as a fail since the test suite compares literal
output from the kconfig version that's bundled with the kernel.

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__`](https://docs.python.org/3.1/reference/datamodel.html#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](http://pypy.org). 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](https://github.com/CoryXie/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](https://github.com/fpemud) has put together [Python
bindings](https://github.com/fpemud/pylkc) 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](https://lkml.org/lkml/2012/12/5/458):

   * 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](https://github.com/philipc) for adding
support for the `allnoconfig_y` option and fixing an obscure issue
with `comment`s inside `choice`s (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) 2011-2017, Ulf Magnusson <ulfalizer@gmail.com>

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.