[Buildroot] [PATCH next v4 6/6] core: implement per-package SDK and target

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

Hello,

Yann was already in Cc, I've added Thomas De Schampheleire as well.
Yann, Thomas, there is some kconfig related discussion below, we
need you :-)

On Thu, 15 Nov 2018 17:41:35 +0100, Andreas Naumann wrote:

> This is much clearer to me than v3, however there is a problem with 
> kconfig packages. Unfortunately, the kconfig infrastructure is running 
> the 'make xxx_defconfig' step before the configure-step is "officially" 
> started. This is due to the kconfig_fixup target being a dependency of 
> -configure. This in turn requires availability of the toolchain and 
> other prerequisites that are part of _FINAL_DEPENDENCIES earlier as 
> prepared in your above patch.
> 
> I made a patch which moves the _FINAL_DEPENDENCIES preparation to an 
> additional .stamp-configure-prepare step just before .stamp_configured. 
> That works but is not particularly beautiful.

That is not too bad actually. Semantically speaking, preparing the
per-package folders is not really part of the configuration step. It
could be logical to do it in a "prepare" step.

The only thing that I dislike a bit with this is that it would no
longer be consistent with what we do for download and extract
dependencies: we prepare the per-package folders with download and
extract dependencies respectively in the download and extract steps. So
it would be quite logical to also do the same for the "configuration
dependencies" (which we name just "dependencies" in Buildroot).

So, this leaves us with 3 options:

 - Keep the dependency preparation within the download, extract and
   configure step, as proposed in this v4. This will require changing
   the kconfig logic to prepare the configuration file inside the
   "configure" step and not as a additional step injected before the
   "configure" step.

 - Keep the dependency preparation within the download and extract
   steps, and make an exception for the configure step, with a separate
   "prepare" step that comes before. Not nice in terms of consistency,
   as explained above.

 - Introduce "prepare download", "prepare extract" and "prepare
   configure" steps that would do the dependency preparation.

> I guess a more proper solution would be to somehow move the 
> kconfig_fixup code into the configure-step. Maybe use the 
> pre-configure-hook, any suggestions?

I don't recall why they need to be done before the configuration step,
but I'm pretty sure there is a reason for that.

Yann, Thomas, do you remember ?

Thanks a lot,

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