[Improvement] Build server should allow building kernel modules for specific kernel version

[Aleksander Mogylchenko]

Currently there is no way to build linux kernel modules on OBS.

Since we need to support Linux distributions, we need the ability to build kernel modules, and we need the ability to select kernel version.

DKMS modules provide a workaround, but even in that case all build should occur as a post-install stage.

[Albert Syriy (asyriy)]

The another connected issue what we have faced is the Makefiles for building kernel modules usually contain a "guess" of kernel version like
make -C /usr/src/kernel-'uname -r'
or
install /lib/modules/'uname -r'

So building kernel modules required the exactly the same kernel version running on the build system.

[Dmitry Burmistrov (dburmistrov)]

You can't use `uname -r` for building kernel modules inside build system because running kernel can be differ from target one.
Instead of it you could specify exact kernel version inside package specifications. This way requires to rebuild all such modules every time when target kernel is changing (e.g. updated by upstream)
To aviod such rebuilds you could use DKMS. In this case 'uname -r' inside post-install section of package is a proper way to adopt kernel module to target(running) kernel

[Alexei Sheplyakov (asheplyakov)]

> The another connected issue what we have faced is the Makefiles for building kernel modules
> usually contain a "guess" of kernel version like
> make -C /usr/src/kernel-'uname -r'

Such makefiles are buggy and should be fixed.