Cross compilation of kernel modules for distro kernels

Cross compilation of kernel modules for distro kernels

[Moessbauer, Felix]

Hi,

I just stumbled upon a cross-compilation issue of a kernel module.
This might be a general issue we should discuss with debian upstream and also handle in the module.inc file.

Situation:
- custom kernel module
- for a stock/distro kernel
- for non amd64 targets

This package depends on the linux-headers-<target> package which transitively attracts the cpp-<x>:<target-arch>.
The cpp-<x>:<target-arch> package however cannot be co-installed with cpp-<x>:amd64.
By that, cross-compiling of the module is simply not possible due to the dependencies of the linux-headers-<target> package.

Notes:
- custom kernels are not affected because they model the dependencies of the headers package differently.
- builds using the sbuilder should also be not affected because each build runs in its own environment (but this is to be checked)

A workaround is to conditionally disable cross compilation for the module:
https://github.com/siemens/meta-coral/pull/16/commits/5a71a1f28b7b2e0406b8f1d707b33817fe74d867

Best regards,
Felix

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