======================================================================================
= Sample project ilustrating how to create configurable builds using Kconfig/Kbuild. 
=
= David Corvoysier copyright Intel 2015
======================================================================================

The build can be configured to compile only some modules under the src directory.
The configuration rules are recursively defined in Kconfig files using the Kconfig
syntax:
    https://www.kernel.org/doc/Documentation/kbuild/kconfig-language.txt

Creating the build configuration requires Kconfig's mconf and conf tools, available
for instance from the kconfig-frontends package:
    http://ymorin.is-a-geek.org/projects/kconfig-frontends  

Once a configuration has been defined, the build applies it using rules defined in
recursive Kbuild.mk makefiles, following the Linux kernel convention for files and
directories selection, and conditioned by the configuration:
    obj-${CONFIG_FOO} += foo.o
    obj-${CONFIG_BAR} += bar/

The project build tree can be extended by specifying an additional external path to
explore when parsing the configuration. At this path, the build system expects a
valid Kconfig/Kbuild.mk pair (see the example under external/sample).

Note: you need to use an absolute path. 

============
How to build
============

Without external services:

make menuconfig
make config
make

With external services:

EXTERNAL_SERVICES=/path/to/ext make menuconfig
EXTERNAL_SERVICES=/path/to/ext make config
make

For instance:

EXTERNAL_SERVICES=$(pwd)/external/sample make menuconfig
EXTERNAL_SERVICES=$(pwd)/external/sample make config
make