Understanding how .config for uboot is generated in buildroot

[Ignatius Rivaldi]

On Tue, Oct 17, 2023 at 7:17 PM Paul Barker <paul.barker.ct at bp.renesas.com>
wrote:

> On Tue, Oct 17, 2023 at 04:35:20PM +1100, Ignatius Rivaldi wrote:
> > Hi all,
> >
> > When I edit the config file in BR2_TARGET_UBOOT_CUSTOM_CONFIG_FILE in a
> > buildroot recipe, how does the config statements from that file got
> > converted into .config file in u-boot?
> >
> > The background is that we're using a custom buildroot config file at
> here:
> > https://github.com/kubos/kubos-linux-build/tree/master to build u-boot
> for
> > a space grade computer. When I added a new config statement
> > (CONFIG_SD_SWITCH=y) in the BR2_TARGET_UBOOT_CUSTOM_CONFIG_FILE, it
> doesn't
> > write the config statement to the .config file in the uboot build repo.
> >
> >  Unfortunately the company that owns that has been acquired several times
> > and all the engineers there already left, so I can't just ask them
>
> You're probably better off asking this on the buildroot mailing list.
> See https://lists.buildroot.org/mailman/listinfo/buildroot.
>
> Best regards,
> Paul
>

Thanks for the pointer, I kind of solved this by adding CONFIG_SD_SWITCH to
uboot kconfig definition file, and now when I added CONFIG_SD_SWITCH to the
_config file it works.
I'll ask about buildroot stuff on the buildroot mailing list after this.

The next problem is that the way Kubos implemented SD card slot switching
is by calling into their own proprietary(?) binary blob through the
standalone application thing:
https://www.emblogic.com/blog/12/u-boot-standalone-applications/. What
happens now is that Uboot is stuck at ## Starting application at
0×21800000. What are the possible causes of this, and how do I start
debugging this?

Fortunately Kubos gave us the source code for that binary blob before they
go bankrupt, so we can tweak it