[Buildroot] [PATCH 2/2] linux: fix use of extensions

[Yann E. MORIN <yann.morin.1998@free.fr>]

Thomas, All,

On 2015-03-13 21:47 +0100, Thomas Petazzoni spake thusly:
> On Fri, 13 Mar 2015 19:57:29 +0100, Yann E. MORIN wrote:
[--SNIP--]
> > This is because dependencies are only acted on at configure time, which
> > is a step further after the kconfig stage. This probably was not an
> > issue before we switched to the kconfig infra for the kernel, but that
> > use-case was completely missed at the time (blame me!).
> 
> Hum, I am not sure to see why the switch to the kconfig-package
> infrastructure would have modified this behavior. So I'd like to
> understand how it used to work, if it ever worked (but I believe it
> did, no?).

OK, so I think I know what happened when we migrated linux over to the
kconfig-package infra, and what we loose then.

Back before we used the kconfig-package infra, linux-menuconfig (as well
as the other configurators) was written as custom rules, that were
basically something like:

    linux-menuconfig: linux-configure
        $(MAKE) -C $(LINUX_DIR) menuconfig

And there we had our dependency on a previously configured linux tree,
and *that* was kicking-in our dependency on extensions.

Fast forward post 2015.02, and we now have linux use the kconfig-package infra,
which completely decorrelates the kconfig-part of the configuration,
from the actual package-part of the configuration, as it introduces an
intermediate 'kconfig-fixup' step:

    linux-configure -------> kconfig-fixup --> .config --> $(LINUX_CONFIG_FILE)
                        /
    linux-menuconfig --'

So, linux-menuconfig now no longer depends on the linux tree to be
configured. Hence the extensions breaking...

And this, I hope, concludes the nalaysis and is enough to convince you
this is a new problem, caused by the kconfig-package infra. Hehe! :-)

Regards,
Yann E. MORIN.

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