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Message-ID: <87d7d90bf8779a997b17c917680995abc455cf11.camel@infradead.org>
Subject: Re: [PATCH] kbuild: announce removal of SUBDIRS if used
From:   David Woodhouse <dwmw2@infradead.org>
To:     Masahiro Yamada <yamada.masahiro@socionext.com>,
        linux-kbuild@vger.kernel.org
Cc:     Sam Ravnborg <sam@ravnborg.org>,
        Marek Vasut <marek.vasut@gmail.com>,
        Guenter Roeck <linux@roeck-us.net>,
        linux-watchdog@vger.kernel.org,
        Wim Van Sebroeck <wim@linux-watchdog.org>,
        linux-doc@vger.kernel.org, Jim Cromie <jim.cromie@gmail.com>,
        Jonathan Corbet <corbet@lwn.net>, linux-kernel@vger.kernel.org,
        Michal Marek <michal.lkml@markovi.net>,
        Brian Norris <computersforpeace@gmail.com>,
        Richard Weinberger <richard@nod.at>,
        linux-mtd@lists.infradead.org,
        Boris Brezillon <boris.brezillon@bootlin.com>
Date:   Fri, 23 Nov 2018 08:04:39 +0000
In-Reply-To: <1542726258-8418-1-git-send-email-yamada.masahiro@socionext.com>
References: <1542726258-8418-1-git-send-email-yamada.masahiro@socionext.com>
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On Wed, 2018-11-21 at 00:04 +0900, Masahiro Yamada wrote:
> SUBDIRS has been kept as a backward compatibility since
> commit ("[PATCH] kbuild: external module support") in 2002.
>=20
> We do not need multiple ways to do the same thing, so I will remove
> SUBDIRS after the Linux 5.3 release. I cleaned up in-tree code, and
> updated the document so that nobody would try to use it.
>=20
> Meanwhile, display the following warning if SUBDIRS is used.
>=20
> Makefile:189: =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D WARNING=
 =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
> Makefile:190: 'SUBDIRS' will be removed after Linux 5.3
> Makefile:191: Please use 'M=3D' or 'KBUILD_EXTMOD' instead
> Makefile:192: =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
>=20
> Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>

No, please don't do this. This is effectively a kernel=E2=86=90=E2=86=92use=
r ABI.

The instructions for building a kernel module have been this, for
*ages*:

 echo 'obj-m :=3D mymod.o' > Makefile
 make -C /lib/modules/`uname -r`/build SUBDIRS=3D`pwd`

People have muscle memory, they have it encoded into various of their
own makefiles and build scripts. Please don't make it stop working
unless there's actually a really good reason to do so.


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