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Date:   Fri, 15 Sep 2023 09:44:08 +0200
From:   "Arnd Bergmann" <arnd@arndb.de>
To:     "Jani Nikula" <jani.nikula@linux.intel.com>,
        "Masahiro Yamada" <masahiroy@kernel.org>
Cc:     "Arnd Bergmann" <arnd@kernel.org>,
        "Jonathan Corbet" <corbet@lwn.net>,
        "Sakari Ailus" <sakari.ailus@iki.fi>,
        "Javier Martinez Canillas" <javierm@redhat.com>,
        "Nathan Chancellor" <nathan@kernel.org>,
        "Nick Desaulniers" <ndesaulniers@google.com>,
        "Nicolas Schier" <nicolas@fjasle.eu>, linux-kbuild@vger.kernel.org,
        linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] Documentation: kbuild: explain handling optional dependencies
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On Fri, Sep 15, 2023, at 09:34, Jani Nikula wrote:
>
> IS_REACHABLE() considered harmful.

Absolutely agreed, and I'm sorry I introduced it in the
first place in commit 9b174527e7b75 ("[media] Add and use
IS_REACHABLE macro").

At the time, it was only used by drivers/media, which used
to have a lot of open-coded instances of it and a lot of
wrong checks.

Having a formal syntax for it was an improvement for
drivers/media since it was more broken before, but it's
usually a mistake to use it when there is another solution,
and we probably should have tried harder to fix the
dependencies in drivers/media at the time.

      Arnd