[Buildroot] [PATCH 1/1] Added local directory as source of kernel code

[Thomas Petazzoni]

Hello Nicolas,

On Wed, 7 Nov 2018 14:40:39 +0000, Nicolas Carrier wrote:

> I have a workspace managed by google repo, which fetches the sources
> of the external git repositories for which we have created .mk
> buildroot Makefiles.
> 
> Because the sources are cloned by repo, I don't want them to be
> fetched by buildroot, hence I used "_SITE_METHOD = local" for all the
> packages.
> 
> For linux and u-boot, I can't do that because they dont support the
> local method and I think there is no reason to make these two
> packages an exception.

Well your patch is actually making u-boot and linux be exceptions. What
if someone wants to build busybox from a local source tree ? And qt5 ?
And openssl ? And then this other package ?

As you can see, this approach does not really scale: we would have to
add Config.in options to all packages to say "please build using the
source code from folder XYZ instead of the normal upstream source
code". That's why we have chosen to support this use case using
OVERRIDE_SRCDIR.

> As for modifying the local.mk file to put some LINUX_OVERRIDE_SRCDIR
> value inside, I want to avoid it because it would force me to version
> the local.mk file for things to work out-of-the-box. Versionning this
> file is problematic because developers needing to modify it
> temporarily may commit it by error.

Here is what you could do:

 - Set BR2_PACKAGE_OVERRIDE_FILE to point to whatever file you like
   instead of local.mk, say package-overrides.mk.

 - In this file, you set LINUX_OVERRIDE_SRCDIR as appropriate, but you
   also do

   -include local.mk

And then you version control package-overrides.mk. Then your developer
can continue locally to tinker with local.mk to have their own custom
OVERRIDE_SRCDIR, and still have LINUX_OVERRIDE_SRCDIR used.

Alternatively, maybe we should decide that linux and u-boot are special
packages, and just like for those packages we support fetching from
custom tarballs and custom Git repositories, we should support fetching
from custom local directories (this is what your patch implements, but
until now, we have resisted going into this direction).

Best regards,

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