Re: make olddefconfig surprises

[Nicolas Schier <nsc@kernel.org>]

On Fri, Jan 23, 2026 at 03:57:59PM -0800, Song Liu wrote:
> On Fri, Jan 23, 2026 at 3:44 PM Nathan Chancellor <nathan@kernel.org> wrote:
> [...]
> > I do not think something like this exists (maybe a SAT solver? :P), at
> > least not as part of the kernel tree. This is basically the same thing
> > as not being able to turn on a configuration in menuconfig until you
> > have gone through and enabled all of its dependencies. I personally use
> > menuconfig when trying to create a configuration fragment for minimized
> > reproducers on top of defconfigs because it is easy to see the final
> > diff when everything is switched:
> >
> >   $ make defconfig
> >   $ make menuconfig
> >   $ git diff --no-index .config.old .config
> 
> I also use menuconfig to figure out the dependencies. The problem of
> this approach is that, if defconfig changes, specifically, if a dependency
> is changed from y to n in defconfig, the fragment may stop working.
> IOW, the fragment assumes some dependency is enabled by default,
> but there is no guarantee that the dependency will always be y in
> defconfig. This should happen rarely though.
> 
> I guess figuring out all dependencies is not too difficult? But I guess
> the reward is not very big either.
> 
> > You could start with defconfig or a more minimal configuration like
> > allnoconfig depending on how the selftests config is expected to be
> > used (as a base or merged into other configs).
> 
> Thanks for sharing these tips.
> 
> Song
> 

Have you tried to use something like

  make KCONFIG_ALLCONFIG=whatever/minimal.config make allnoconfig

?

Kind regards,
Nicolas