[yocto] Build external module against Yocto kernel

[Patrick Turley]

Thank you for directing me toward that documentation. As it happens, I have already read that, and it doesn't apply.

The section you mentioned begins with this text:

While it is always preferable to work with sources integrated into the Linux kernel sources, if you need an external kernel module, the hello-mod.bb recipe is available as a template from which you can create your own out-of-tree Linux kernel module recipe.

The approach here is to create a recipe that will build a module outside the kernel tree, but still within the Yocto system.

That isn't what I'm doing.

I have source code for a kernel module that is entirely outside Yocto.  I'm *not* going to write a recipe for this module and integrate it into a Yocto layer.

Here's a link to instructions on how I would do this in Ubuntu:

http://www.cyberciti.biz/tips/build-linux-kernel-module-against-installed-kernel-source-tree.html

As you can see, Ubuntu (and, of course, other major distributions) have "kernel-headers" packages that carry all the artifacts one needs to build a module "after the fact."

Does Yocto have a mechanism for packaging up the necessary artifacts and making them available *outside* the Yocto build system and long *after* the Yocto build is finished?  Does Yocto recognize the necessity of this?  The best I've been able to do is point my module build process at something like this:

LINUX_DIR=/home/pturley/yocto-mpu-build/tmp/work/dm8148_mpu-poky-linux-gnueabi/linux-ti81xx-psp-2.6.37-r0+spawnlabs+r0/git

This works but it's messy, unreliable and inconvenient.

So, my question remains: Does Yocto have a graceful way of dealing with this situation, perhaps like Ubuntu and friends?


On Jan 15, 2013, at 11:09 AM, Brian Lloyd <blloyd at familyhonor.net<mailto:blloyd at familyhonor.net>> wrote:

Or better yet, now that it is past initial, use http://www.yoctoproject.org/docs/1.4/kernel-dev/kernel-dev.html#incorporating-out-of-tree-modules. <http://www.yoctoproject.org/docs/1.4/kernel-dev/kernel-dev.html#incorporating-out-of-tree-modules.%C2%A0>  :)
It worked fine for 1.2 (denzil) for me, though it is written for a later one.

Brian

On Tue, 2013-01-15 at 11:07 -0600, Brian Lloyd wrote:
Try this in work documentation and let us know how it helps or if there is something missing that would help more:
http://www.yoctoproject.org/docs/hart/kernel-dev/kernel-dev.html#incorporating-out-of-tree-modules

I just did the exact same thing and was happy to discover there is support in yocto for doing just this.

Brian

On Mon, 2013-01-14 at 23:27 +0000, Patrick Turley wrote:

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?

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