Re: [RFC][PATCH] kconfig: introduce listunknownconfig

[Masahiro Yamada]

On Tue, Aug 22, 2023 at 4:30 PM Sergey Senozhatsky
<senozhatsky@xxxxxxxxxxxx> wrote:
>
> On (23/08/21 21:27), Masahiro Yamada wrote:
> >
> > My (original) hope was to add a single switch, KCONFIG_VERBOSE, to address both:
> >
> >   - A CONFIG option is hidden by unmet dependency (Ying Sun's case)
> >   - A CONFIG option no longer exists  (your case)
> >   - Anything else we need to be careful
>
> A quick question: is it too late to suggest an alternative name?
> Could KCONFIG_SANITY_CHECKS be a little cleaner? Because we basically
> run sanity checks on the config.


Ying's is not applied yet. So, it is not too late.

But, I started to be a little worried
because it is unpredictable how many KCONFIG_* env
variables will increase until people are satisfied.

>
> And one more question: those sanity checks seem very reasonable.
> Is there any reason we would not want to keep them ON by default?
> And those brave souls, that do not wish for the tool to very that
> the .config is sane and nothing will get downgraded/disabled, can
> always set KCONFIG_SANITY_CHECKS to 0.


Kconfig is meant to resolve the dependency without causing an error.
If a feature is not available, it is automatically, silently hidden,
and that works well.

When a compiler does not support a particular feature,
'depends on $(cc-option )' hides that CONFIG option.
Kconfig is meant to work like that.



For your case, it is case-by-case.

Let's say a stale code is removed from upstream.

After "obj-$(CONFIG_FOO) += foo.o" is removed
from upstream, CONFIG_FOO in the .config is a "don't care".

If it were an error, all arch/*/configs/*_defconfig
must be cleaned up at the same time.


So, sometimes it is helpful, but sometimes noisy.




For the MFD_RK808 case particularly,
I believe Kconfig showed MFD_RK8XX_I2C
as a new option.

Or, when you bumped to a new kernel version,
you could run 'make listnewconfig'.
(See 17baab68d337a0bf4654091e2b4cd67c3fdb44d8.
Redhat says they review every new config option.)


If you had done a per-config review
you would have noticed
c20e8c5b1203af3726561ee5649b147194e0618e
before spending time on run-time debugging.




-- 
Best Regards
Masahiro Yamada