[yocto] Building a Kernel Module that uses /lib/modules/<version>/build/Makefile

[Daniel.]

Ronald

If you have a module developed against 3.10 you may have trouble
compiling it against 4.x. You should port the module to 4.x kernel,
not kernel to module. If you patch the kernel to compile that module
other modules may break. I suggest that you download the kernel and
module to some folders outside of Yocto while developing, create one
or more patches with the fixes and then use Yocto to apply that
patches against that module.

Cheers,

2016-09-06 19:02 GMT-03:00 Ronald Oakes <ronaldo at brc2.com>:
> I seem to have been able to solve my own problem by doing a bit more
> poking around:
>
> It looks like the makefile I'm looking for is found in
> ${STAGING_KERNEL_DIR}, which appears in the Makefile as
> $(KERNEL_PATH).
>
> At least once I replaced the setting that was hard coded to
> /lib/modules/$(KERNEL_VERSION/build with $(KERNEL_PATH), I'm getting a
> build.  (I'm still getting some issues with the fact that my third
> party source doesn't want to build wtih either kernels 4.1.18 or 4.4.x
> as they are both too new, so I may have to patch it's linux_common.h
> to accept 4.1.18 instead of 4.1.1, but that is a minor issue in
> comparison)
>
> Thank you
>   Ron Oakes
>
> On Tue, Sep 6, 2016 at 11:11 AM, Ronald Oakes <ronaldo at brc2.com> wrote:
>> I'm trying to integrate a 3rd party kernel module for some hardware
>> that we are using as part of our project.  Following the directions
>> that work on the native Linux installation for building it doesn't
>> quite work for a number of reasons, so I'm now modifying the generated
>> Makefile.
>>
>> However, it appears that the bulk of the work is done by a standard
>> makefile located in /lib/modules/$(KERNEL_VERSION)/build (which was
>> actually hard-coded by the configure before I started modifying the
>> makefile).  But, I'm not able to locate this in the files that Yocto
>> has produced when building the embedded kernel and the other kernel
>> modules.
>>
>> I've not booted the target and looked there - but I'd rather not build
>> this on the target.  Ideally, I'd like to have everything built on my
>> development system (not that we won't have the horsepower to build on
>> the target, but I'd rather not be putting the compilers there, nor
>> have to be having a module build as part of bring up each time - we
>> won't have any non-volitate memory so everything will have to be
>> loaded each time we boot.
>>
>> Similarly, building the binary and just including that may be
>> difficult as our build system is running a much older kernel than our
>> target (3.10 versus 4.4), so we'd still be in a cross-target situation
>> and the 3rd party supplier assumes that one is building for the system
>> one is running on and provides limited support otherwise in their
>> documentation (I've not contacted them for assistance yet)
>>
>> Any suggestions/recomendations?
>>
>> Ron Oakes
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