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Subject: Re: [PATCH 2/2] kconfig: unify cc-option and as-option
From:   Johannes Berg <johannes@sipsolutions.net>
To:     Masahiro Yamada <masahiroy@kernel.org>
Cc:     Linux Kbuild mailing list <linux-kbuild@vger.kernel.org>,
        Nick Desaulniers <ndesaulniers@google.com>,
        Arvind Sankar <nivedita@alum.mit.edu>,
        Andrew Morton <akpm@linux-foundation.org>,
        Brendan Higgins <brendanhiggins@google.com>,
        Catalin Marinas <catalin.marinas@arm.com>,
        Changbin Du <changbin.du@intel.com>,
        Krzysztof Kozlowski <krzk@kernel.org>,
        Mauro Carvalho Chehab <mchehab+huawei@kernel.org>,
        Randy Dunlap <rdunlap@infradead.org>,
        Will Deacon <will@kernel.org>,
        linux-arm-kernel <linux-arm-kernel@lists.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Date:   Tue, 04 May 2021 22:52:41 +0200
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         <20200614144341.1077495-2-masahiroy@kernel.org>
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On Wed, 2021-05-05 at 05:46 +0900, Masahiro Yamada wrote:
> 
>  - This commit touches scripts/Kconfig.include.
>  - External module builds (M= builds) never invoke Kconfig
> 
> Putting these two together, your claim is really odd.

Hmm.

> If external module builds invoke Kconfig,
> your kernel is already broken.

Well, it's not about the kernel, that's just the normal upstream (or
perhaps distribution) kernel.

Anyway, you're right, it's much simpler. The problem isn't invoking M=
or something like that, that happens much later and sent me on the
completely wrong track.

The problem is simply doing

	make kernelversion

to determine the version of a tree that's not writable to the user, e.g.

	make -C /lib/modules/$(uname -r)/build/ kernelversion

Which basically also means that it's harmless, since the version is of
course not affected by cc-option.

johannes