[Buildroot] Adding package that builds Kernel Module (*.ko) to Buildroot environment

[Ron Schmitt]

Hello,
I am embarking on my first embedded driver development project.
Could someone possibly give the explicit commands for how to do this, i..e.
how to add a package that builds Kernel Module (*.ko) to Buildroot
environmentLet's assume the following:
- I have installed buildroot at

/path/buildroot

- I have executed "make menuconfig" and set up my build.
- I have not yet run the build, i.e. I have not executed "make"
- I have copied your "*hello world" kernel module *c file to

/path/buildroot/mykmod.c

- I have copied your patch file to

/path/buildroot/kmod-example.patch


Thank you very much for your time and assistance.
Ron
[Buildroot] Adding package that builds Kernel Module (*.ko) to Buildroot
environment*Thomas Petazzoni* thomas.petazzoni at free-electrons.com
<buildroot%40busybox.net?Subject=Re%3A%20%5BBuildroot%5D%20Adding%20package%20that%20builds%20Kernel%20Module%20%28%2A.ko%29%20to%0A%20Buildroot%20environment&In-Reply-To=%3C20110804094557.4464b69b%40skate%3E>
*Thu Aug 4 07:45:57 UTC 2011*


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------------------------------

Hello,

Le Thu, 04 Aug 2011 08:30:21 +0200,
Aleksandar Zivkovic <Aleksandar.Zivkovic at rt-rk.com

* I would like to add additional package to Buildroot that will build

*>* Linux kernel driver.
*>* For that I need:
*>* - dependency: build of this package mustn't be started before kernel
*>* source is available
*>* - kernel source directory: currently, the best I know is:
*>* $(BASE_DIR)/build/linux-$(BR2_LINUX_KERNEL_VERSION)
*> >* I started with package approach but bumped to stated dependency
*>* problem. Next what I tried is to edit linux/linux.mk
<http://linux.mk> to include my
*>* driver source download, extract. build and install but not so
*>* familiar with Buildroot scripting...
*> >* Did somebody already done something similar? What is best approach?
*>* Examples are welcomed...
*
Attached, you will find :

* mykmod-1.0.tar.bz2, the source code of an hello world like kernel
module ;

* kmod-example.patch, which adds support for compiling this kernel
module into the Buildroot package infrastructure

Do not hesitate to get back to the mailing list if you have any issues
getting this to work or need additional details.

Best regards,

Thomas
--
Thomas Petazzoni, Free Electrons
Kernel, drivers, real-time and embedded Linux
development, consulting, training and support.http://free-electrons.com
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[Arnout Vandecappelle]

Hi Ron,

Please use text-only messages on this list, it looks much cleaner.

Post by Ron Schmitt
Hello,
I am embarking on my first embedded driver development project.
Could someone possibly give the explicit commands for how to do this, i..e.
how to add a package that builds Kernel Module (*.ko) to Buildroot environment
- I have installed buildroot at
/path/buildroot
- I have executed "make menuconfig" and set up my build.
- I have not yet run the build, i.e. I have not executed "make"
- I have copied your "/hello world" kernel module /c file to
/path/buildroot/mykmod.c
- I have copied your patch file to
/path/buildroot/kmod-example.patch

This example is much too old to still be applicable with current buildroot,
though the changes are not that dramatic.

With current buildroot, you should create a new directory outside of buildroot,
which contains a Config.in and external.mk file and a directory mykmod that
contains the files Config.in and mykmod.mk. See [1]

For your convencience, I've created that structure in [2]. You can just clone
it and start from there.


The next step is to go to the buildroot directory and run:

BR2_EXTERNAL=<path_to_buildroot-mykmod> make menuconfig

You will now see an additional menu entry at the bottom: User-provided options.
In this menu, select the mykmod package. Now run 'make' and it will be built.

Please consult the buildroot manual to understand what is going on here [3].
For your real kernel module, you'll also want to replace the _SOURCE and _SITE
variables with a reference to your VCS.


Note that very soon now, a new infrastructure will be merged to simplify the
building of external linux kernel modules. With that infrastructure, mykmod.mk
will become:

###############################################################################
#
# mykmod
#
###############################################################################

MYKMOD_VERSION = 1.0
MYKMOD_SOURCE = mykmod-$(MYKMOD_VERSION).tar.bz2
MYKMOD_SITE = file://$(BR2_EXTERNAL)

$(eval $(kernel-module))
$(eval $(generic-package))



Regards,
Arnout

[1] http://nightly.buildroot.org/manual.html#outside-br-custom
[2] http://gitlab.com/arnout/buildroot-mykmod.git
[3] http://nightly.buildroot.org/manual.html#adding-packages

Post by Ron Schmitt
Thank you very much for your time and assistance.
Ron

[snip]