[Buildroot] Fw: Aw: Re: Cross-Compiling out-of-tree driver

[universeII at gmx.de <universeII@gmx.de>]

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Gesendet:?Freitag, 05. April 2013 um 15:30 Uhr
Von:?universeII at gmx.de
An:?"Thomas Petazzoni" <thomas.petazzoni@free-electrons.com>
Betreff:?Aw: Re: [Buildroot] Cross-Compiling out-of-tree driver

Thomas,
sorry for contacting your directly. I wasn't sure if my email is? shown in the list archive in the correct subtree when replying to the list. Is this correct or how do I reply correctly?
?
Setting KDIR to the right directory does not work sufficiently as I have to set the architecture correctly. I'm trying to cross-compile
for PowerPC architecture but my PC is x86_64.
I tried several recommendation from the internet (setting environment variables) but did not succeed.
What do I have to set in my Makefile to use the cross-compile toolchain from buildroot and tell the gcc to use the PowerPC part of kernel tree instead of x86_64?
?
Regards,
Andreas

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P.S.: Acutally I just need to copy the .ko file to the target and do insmod/rmmod manually.
?

Gesendet:?Freitag, 05. April 2013 um 15:19 Uhr
Von:?"Thomas Petazzoni" <thomas.petazzoni@free-electrons.com>
An:?universeII at gmx.de
Cc:?buildroot at uclibc.org
Betreff:?Re: [Buildroot] Cross-Compiling out-of-tree driver
Andreas,

Please do not reply to me directly: the list should be kept in Cc.
Thanks.

On Fri, 5 Apr 2013 14:54:39 +0200 (CEST), universeII at gmx.de wrote:

> thanks for your quick response. I'm still a little bit confused how to complile the driver.
> I have the dummy driver in an own directory including the Makefile which is just a "normal"
> makefile for compiling a driver out-of-tree.
> Example:
>
> obj-m := dummy_driver.o
> KDIR := /lib/modules/$(shell uname -r)/build
> PWD := $(shell pwd)
>
> default:
> $(MAKE) -C $(KDIR) M=$(PWD) modules
>
>
> I change to the directory and issue a "make" command. I was woundering if it is possible to just set
> KDIR and the gcc approriately to the kernel sources and (cross-compile) tools from buildroot.

Aah, ok, you want to build your module manually outside of Buildroot.
What I showed in my previous e-mail was how to integrate it as a
Buildroot package.

If you want to build your out-of-tree module manually against a Linux
kernel that has been built by Buildroot, then you should just do:

KDIR = /path/to/buildroot/output/build/linux-x.y.z/

that should be enough. Then of course, you should install your module,
so maybe add something like:

DESTDIR = /path/to/buildroot/output/target/

install:
$(MAKE) -C $(KDIR) M=$(PWD) INSTALL_MOD_PATH=$(DESTDIR) modules_install

run "make install" in your module, which should install it in the
output/target/lib/modules/<kernelversion>/ directory. Then, run "make"
again in Buildroot so that your filesystem image gets regenerated to
include the module.

Of course, this is only needed if you want a clean installation of your
module. For quick and dirty testing, you can also just copy the .ko
file to your target, and insmod it.

> I had a look at your patch file and it seems to me that the .mk is somehow included in the
> buildroot make structure (I'm sorry that I do not know so much details how buildroot work internally)?

Yes, my patch shows how to add an out-of-tree kernel driver as a
Buildroot package, so that it is nicely integrated in the Buildroot
build process.

> How do you in this case issue a compilation of your driver?

You just enable your new package in 'make menuconfig', and run the
usual Buildroot 'make' command.

Best regards,

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