[Buildroot] ADEOS patch and kernel override

[Thomas Petazzoni <thomas.petazzoni@bootlin.com>]

Hello Michael,

On Fri, 7 Sep 2018 12:44:43 +0200, Michael Nazzareno Trimarchi wrote:

> I'm trying to understand if I can override the kernel and let apply
> the adeos patch on top of it. Seems that PREHOOK is not called
> in the linux kernel override directory. Is there some semantic to use?

When you said "override the kernel", I will assume you talking about
using LINUX_OVERRIDE_SRCDIR. If that is the case, then no, Buildroot
will not patch it for you.

Let me give a few more details about this, and explain why it is done
like this.

In a normal situation (i.e without OVERRIDE_SRCDIR), a package goes
through the following steps:

 (1) download
 (2) extract
 (3) patch
 (4) configure
 (5) build
 (6) install

When you switch to using OVERRIDE_SRCDIR for that package, the first
three steps are skipped and replaced by a "rsync" step, while the three
last steps remain the same:

 (1) rsync
 (2) configure
 (3) build
 (4) install

The reason is that if you do an override source directory:

 * Buildroot has no idea what is the state of the source code in here,
   so it has no idea if the patches it has will apply. Most likely not.

 * More importantly, it means that you own/control the source code,
   so you can simply apply whatever changes are needed on the source
   code located in the OVERRIDE_SRCDIR location.

Does that help ?

Best regards,

Thomas
-- 
Thomas Petazzoni, CTO, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com