[yocto] Build external module against Yocto kernel

[Patrick Turley]

I have to build a module from a third-party that has nothing to do with Yocto.

I want to build this module against the kernel Yocto is giving me.

The Make file for this module has a build command like this:

    make -C $(LINUX_DIR) M=`pwd` $(ENV) \
        EXTRA_CFLAGS="$(EXTRA_CFLAGS)" modules

Obviously, this command needs to connect with either the Linux source tree or something like a "kernel-headers" package.

I used the meta-toolchain-sdk recipe to produce an SDK, and I installed it. Unfortunately, I don't see a "kernel-header" equivalent in there.

This leads me to imagine I must point this command at some sub-tree within the Yocto output (probably under tmp/sysroots). And, if I want that tree available elsewhere, I have to package it up into a tarball and transport it.

Usually, Yocto is way ahead of me on these sorts of things, and there's already a graceful way to deal with this -- I just haven't figure it out yet.

What am I missing?