[Buildroot] building fbtft framebuffer drivers into buildroot.

[Thomas Petazzoni <thomas.petazzoni@free-electrons.com>]

Dear Yann E. MORIN,

On Fri, 26 Dec 2014 11:20:29 +0100, Yann E. MORIN wrote:

> I've had a look at this package, and unfortunately, it will be hard to
> get it packaged in Buildroot.
> 
> The problem is that this kernel module does not compile as an
> out-of-tree module, and their buildsystem is made so that it requires
> the kernel be patched.
> 
> This is not posible with Buildroot.

Well, yes and no. Indeed it is much easier to package if the stuff can
be built as an out-of-tree module. However, we have two examples of
things packaged in Buildroot that require patching the kernel: Xenomai
and RTAI. They use a loosely defined model that we could name "Linux
extension", see linux/linux-ext-*.mk. They basically hook up into the
Linux build process by adding some stuff to LINUX_PRE_PATCH_HOOKS.

I recently had a look at the aufs stuff, and it has the same problem:
not only it is made of modules that can be built out-of-tree, but it
also needs to patch the kernel (some core VFS changes).

So, I haven't looked at all the fbtft stuff. If it's a set of
standalone drivers that don't require any modification to the core of
the kernel, then indeed, turning them into out-of-tree modules can be a
good idea. If not, then using the "linux-ext" model can be a solution.

Best regards,

Thomas
-- 
Thomas Petazzoni, CTO, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com