[yocto] Including a header from an external kernel module

[Andre McCurdy]

On Mon, Jul 9, 2018 at 3:07 PM, Michael Allwright
<michael.allwright at ulb.ac.be> wrote:
> Yes, it ended up in the development package in the do_install_append
> attempt

How did you confirm that (ie that the header ended up in the
module-a-dev package) ?

> , but I couldn't #include it in the second module (file didn't exist
> in the include search paths).

Did you add:

  DEPENDS = "module-a"

to the module-b recipe?

> I would point out though, that I am interested in what is the correct way to
> do this, and not just in finding some workaround / hack so that it works...

That's good to hear.

> On Mon., 9 Jul. 2018, 19:47 Andre McCurdy, <armccurdy at gmail.com> wrote:
>>
>> 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>
>> >