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References: <20210825041637.365171-1-masahiroy@kernel.org> <boris.20210825172545@codesynthesis.com>
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From:   Masahiro Yamada <masahiroy@kernel.org>
Date:   Thu, 26 Aug 2021 11:24:15 +0900
Message-ID: <CAK7LNAS-NhR=94uHYcZUhRkdUEm=dYZSRbGKkB5zJJGNRw0z2A@mail.gmail.com>
Subject: Re: [PATCH] kconfig: forbid symbols that end with '_MODULE'
To:     Boris Kolpackov <boris@codesynthesis.com>
Cc:     Linux Kbuild mailing list <linux-kbuild@vger.kernel.org>,
        "David S. Miller" <davem@davemloft.net>,
        Jakub Kicinski <kuba@kernel.org>,
        Jaroslav Kysela <perex@perex.cz>,
        Kalle Valo <kvalo@codeaurora.org>,
        Liam Girdwood <lgirdwood@gmail.com>,
        Luca Coelho <luciano.coelho@intel.com>,
        Mark Brown <broonie@kernel.org>,
        Peter Ujfalusi <peter.ujfalusi@gmail.com>,
        Takashi Iwai <tiwai@suse.com>,
        ALSA Development Mailing List <alsa-devel@alsa-project.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        linux-wireless@vger.kernel.org, Networking <netdev@vger.kernel.org>
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On Thu, Aug 26, 2021 at 12:42 AM Boris Kolpackov
<boris@codesynthesis.com> wrote:
>
> Masahiro Yamada <masahiroy@kernel.org> writes:
>
> > Kconfig (syncconfig) generates include/generated/autoconf.h to make
> > CONFIG options available to the pre-processor.
> >
> > The macros are suffixed with '_MODULE' for symbols with the value 'm'.
> >
> > Here is a conflict; CONFIG_FOO=m results in '#define CONFIG_FOO_MODULE 1',
> > but CONFIG_FOO_MODULE=y also results in the same define.
> >
> > fixdep always assumes CONFIG_FOO_MODULE comes from CONFIG_FOO=m, so the
> > dependency is not properly tracked for symbols that end with '_MODULE'.
>
> It seem to me the problem is in autoconf.h/fixdep, not in the Kconfig
> language.


Partly a Kconfig problem since autoconf.h is generated by Kconfig.

So, what is your suggestion for doing this correctly?
(of course without breaking the compatibility
because this is how the kernel is configured/built
for more than 20 years)


>
> > This commit makes Kconfig error out if it finds a symbol suffixed with
> > '_MODULE'.
>
> I know you don't care, but I will voice my objection, for the record:
> Kconfig is used by projects other than the Linux kernel and some of
> them do not use the autoconf.h functionality. For such projects this
> restriction seems arbitrary and potentially backwards-incompatible.

I am not sure what your worry is, but this check resides in
"if (modules_sym)" conditional, so projects using Kconfig but
not module functionality (e.g. buildroot) will not be  affected.


-- 
Best Regards
Masahiro Yamada