Re: [PATCH v10 05/13] kbuild: remove MODULE_LICENSE/AUTHOR/DESCRIPTION in non-modules

From: Masahiro Yamada <masahiroy@kernel.org>
To: Luis Chamberlain <mcgrof@kernel.org>
Cc: Arnd Bergmann <arnd@arndb.de>,
	Thomas Gleixner <tglx@linutronix.de>,
	Steven Rostedt <rostedt@goodmis.org>,
	Nick Alcock <nick.alcock@oracle.com>,
	Geert Uytterhoeven <geert@linux-m68k.org>,
	linux-modules@vger.kernel.org,
	linux-trace-kernel@vger.kernel.org, linux-kernel@vger.kernel.org,
	Andrew Morton <akpm@linux-foundation.org>,
	eugene.loh@oracle.com, kris.van.hees@oracle.com
Subject: Re: [PATCH v10 05/13] kbuild: remove MODULE_LICENSE/AUTHOR/DESCRIPTION in non-modules
Date: Sun, 5 Mar 2023 17:09:42 +0900	[thread overview]
Message-ID: <CAK7LNASL7_RgfASstBvN6AzhR=nMU=HsQvODf5q13Xud8tBWRQ@mail.gmail.com> (raw)
In-Reply-To: <Y5AeuI4RD0tpzlp5@bombadil.infradead.org>

On Wed, Dec 7, 2022 at 2:04 PM Luis Chamberlain <mcgrof@kernel.org> wrote:
>
> On Tue, Dec 06, 2022 at 10:02:30PM +0100, Arnd Bergmann wrote:
> > On Tue, Dec 6, 2022, at 21:03, Nick Alcock wrote:
> > > On 6 Dec 2022, Geert Uytterhoeven uttered the following:
> > > Only MODULE_LICENSE invokes MODULE_FILE and thus ends up introducing a
> > > KBUILD_MODOBJS entry that triggers things going wrong iff not a module:
> > > so only it needs to go out (or be replaced with a variant that doesn't
> > > invoke MODULE_FILE, if you want to keep the license in too --
> >
> > That sounds like a better alternative
> >
> > > but if the thing is no longer a standalone entity at all I'm not sure
> > > what meaning it could possibly have).
> >
> > As far as I can tell, the general trend is to make more things modules,
> > so there is a good chance that these come back eventually. If the
> > information in the MODULE_LICENSE field isn't wrong, I would just
> > leave it in there.
>
> Tooling today uses it though to make a deterministic call on if something
> *can* be a module. In particular after commit 8b41fc4454e ("kbuild: create
> modules.builtin without Makefile.modbuiltin or tristate.conf") we rely on
> the module license tag to generate the modules.builtin file. This in
> turn is used to allow modprobe to *not* fail when trying to load a module
> which is built-in.

If we have a bool driver 'foo.ko' in modules.builtin,
'modprobe foo' will not fail where you expect it will fail.

Is it so important to make this strict?

I do not think so.

What is a point for a user to realize
"Oh, I did not know foo cannot be compiled as a module"

Re-read the commit description of
bc081dd6e9f622c73334dc465359168543ccaabf

The motivation of module.builtin is to know the functionality 'foo'
is available (via built-in or module, whatever).

In this sense, having always-builtin entries in module.builtin is OK.

I do not see any sense in the tooling mess in this patch set.

> So we can't just disable the tag for when the code is built-in as *want*
> to carry it when modules are built-in, that is the point, to help
> userspace with this determination.
>
> I don't think we want to revert 8b41fc4454e as it means we'd force Kbuild to
> traverse the source tree twice.

I do not want to revert it.

and I do not want this series in the mainline.

>
> Geert's point was not keeping MODULE_LICENSE() but instead the other
> MODULE_*() crap for things which are not modules in case in the future
> code becomes a module...
>
> But I don't see the point in keeping things around just in case, if we
> want to keep things simple. Just use the SPDX license tag for the license.
>
>   Luis

--
Best Regards
Masahiro Yamada