[Buildroot] [PATCH] u-boot: 2015.07 - fix creation of .config

[Alexey Brodkin <Alexey.Brodkin@synopsys.com>]

Hi Yann,

On Mon, 2015-08-17 at 11:31 +0200, Yann E. MORIN wrote:
> Alexey, All,
> 
> On 2015-08-17 06:37 +0000, Alexey Brodkin spake thusly:
> > On Sun, 2015-08-16 at 23:43 +0200, J?rg Krause wrote:
> > > Hi Thomas, Alexey,
> > > 
> > > On Mi, 2015-08-12 at 10:23 +0200, Thomas Petazzoni wrote:
> > > > Dear Alexey Brodkin,
> > > > 
> > > > On Tue, 11 Aug 2015 12:20:01 +0000, Alexey Brodkin wrote:
> > > > 
> > > > > Any chance for this one to be applied?
> > > > > Note without this change or anything similar U-Boot from
> > > > > snsp_axs10x_defconfig fails to config.
> > > > 
> > > > I haven't had the time to look into this in detail. It would be great
> > > > if Yann, or J?rg could have a look. I remain unhappy with solving
> > > > such
> > > > a problem by using a patch against U-Boot 2015.07, because it means
> > > > anyone specifying a slightly different U-Boot version (but based on
> > > > 2015.07) will still have the problem.
> > > 
> > > It looks like upstream [1] does not revert this patch but fixes the
> > > problem with this patch [2]. Alexey, does this patch solves your
> > > problem?
> > > 
> > > Best regards
> > > J?rg Krause
> > > 
> > > 
> > > [1]
> > > https://www.mail-archive.com/u-boot at lists.denx.de/msg179681.html 
> > > 
> > > [2]
> > > http://patchwork.ozlabs.org/patch/502793/
> > 
> > The thing is [2] solves problem only for ARM, while other arches are still
> > affected. And that means ARC is not cured by that patch.
> > 
> > Indeed proper fix is to patch all arches in the same way,
> > i.e. select default option for each and every architecture in U-Boot.
> > 
> > But speaking about Buildroot that approach has at least 2 downsides:
> >  1) Not all arches are fixed upstream so in Buildroot we'll have patches
> >     that are not there in upstream yet.
> > 
> >  2) We'll have quite a few patches in Buildroot for U-boot each fixing
> >     a separate arch.
> > 
> > If (1) and (2) are OK for Buildroot I'll try to come up with those patches ASAP.
> > 
> > My initial approach was IMHO the cleanest and simplest. But if it doesn't work
> > we'll do another fix :)
> 
> OK, chiming in...
> 
> I guess removing the "optional" keywork would be the simplest solution,
> indeed.
> 
> But then I'm afraid that defconfig files bundled with U-Boot will no
> longer work. If they still work, then I'm OK for having a local patch
> that reverts upstream's (until upstream fixes all of their archs).

Ok that's probably another mystery of Kconfig but defconfigs bundled with
U-Boot do work. They worked both before reverted patch and after.

What doesn't work is "make oldconfig".
See in U-Boot (let's forget about Buildroot for a minute) we usually build stuff
with defconfigs this way "make xxx_defconfig". And it worked and it works still.

But in Buildroot what we do we take "xxx_deconfig", copy it from "configs" folder
to the root of U-Boot build folder as .config, do changes we need and then to get
correctly expanded .config for building we finally do "make oldconfig".

And that's where the problem happens. Kconfig just skips items marked as optional
and so platforms are not set properly and build fails.

In other words I would blame Kconfig and I even spent some time trying to
figure out if there's a way to fix Kconfig simply. But to no avail. And so
I decided to work-around Kconfig issue.

Hope that comment makes sense.

-Alexey