[yocto] Including a header from an external kernel module

[Andre McCurdy]

On Mon, Jul 9, 2018 at 8:27 AM, Michael Allwright
<michael.allwright at ulb.ac.be> wrote:
> Hello,
>
> I think it would be useful to extend the hello-mod recipe in meta-skeleton
> to demonstrate some slightly more complicated scenarios. For example, I am
> trying to find out how to have two external kernel modules A and B, where
> module B #includes a header file provided by module A.
>
> I have made module B depend on module A, however, I believe I am still
> missing one or two steps in my recipe for module A such that the header file
> is copied into the shared kernel staging directory where module B can find
> it.
>
> So far I have tried the following:
>
> FILES_${PN}-dev += "/usr/include/linux/mfd/module-a.h"
>
> FILES_kernel-headers += "${includedir}/linux/mfd/module-a.h"
>
> do_install_append () {
>    install -d ${D}${includedir}/linux/mfd
>    install -m 644 ${S}/module-a ${D}${includedir}/linux/mfd/module-a.h
> }

And what happened after you tried the above? Did the header not end up
in the -dev package for module A? Did the module A recipe not create a
-dev package? Something else?

> In module B, I want to be able to:
>
> #include <linux/mfd/module-a.h>
>