Re: [PATCH v7 1/5] module.h: MODULE_DEVICE_TABLE for built-in modules

From: Allen Webb <allenwebb@google.com>
To: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: "linux-modules@vger.kernel.org" <linux-modules@vger.kernel.org>,
	"linux-usb@vger.kernel.org" <linux-usb@vger.kernel.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	Luis Chamberlain <mcgrof@kernel.org>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	"Rafael J. Wysocki" <rafael@kernel.org>
Subject: Re: [PATCH v7 1/5] module.h: MODULE_DEVICE_TABLE for built-in modules
Date: Mon, 19 Dec 2022 09:56:11 -0600	[thread overview]
Message-ID: <CAJzde07sLeqALQ-rwtdSkx0n3eqOj94TJ0w-BhCwGRJjLDGj0g@mail.gmail.com> (raw)
In-Reply-To: <7394f5cc-35be-0bc8-f92d-bb9e71d3f85c@csgroup.eu>

On Sat, Dec 17, 2022 at 4:05 AM Christophe Leroy
<christophe.leroy@csgroup.eu> wrote:
>
>
>
> Le 16/12/2022 à 23:16, Allen Webb a écrit :
> > Implement MODULE_DEVICE_TABLE for build-in modules to make it possible
> > to generate a builtin.alias file to complement modules.alias.
> >
> > Signed-off-by: Allen Webb <allenwebb@google.com>
> > ---
> >   include/linux/module.h | 10 +++++++++-
> >   1 file changed, 9 insertions(+), 1 deletion(-)
> >
> > diff --git a/include/linux/module.h b/include/linux/module.h
> > index ec61fb53979a9..49e4019393127 100644
> > --- a/include/linux/module.h
> > +++ b/include/linux/module.h
> > @@ -243,7 +243,15 @@ extern void cleanup_module(void);
> >   extern typeof(name) __mod_##type##__##name##_device_table           \
> >     __attribute__ ((unused, alias(__stringify(name))))
> >   #else  /* !MODULE */
> > -#define MODULE_DEVICE_TABLE(type, name)
> > +/* The names may not be unique for built-in modules, so include the module name
> > + * to guarantee uniqueness.
> > + */
>
> This is network only comment style.

I have fixed this in my local copy and will include it with the next upload.

>
> Other parts of kenel have different style, see
> https://docs.kernel.org/process/coding-style.html#commenting
>
> > +#define MODULE_DEVICE_TABLE(type, name)                                      \
> > +extern void *CONCATENATE(                                            \
>
> 'extern' keyword is pointless of function prototypes and deprecated.
> Don't add new occurences.

This is a weird case because these symbols are used for post
compilation processing by modpost. If I drop the extern keyword, the
build fails with a bunch of errors of the form:

/mnt/host/source/src/third_party/kernel/upstream/drivers/hid/hid-generic.c:79:1:
error: definition
'__mod_hid__hid_table__kmod_hid_generic_device_table' cannot also be
an alias
MODULE_DEVICE_TABLE(hid, hid_table);
^
/mnt/host/source/src/third_party/kernel/upstream/include/linux/module.h:255:26:
note: expanded from macro 'MODULE_DEVICE_TABLE'
        __attribute__ ((unused, alias(__stringify(name))))

>
>
> > +     CONCATENATE(__mod_##type##__##name##__,                         \
> > +             __KBUILD_MODNAME),                                      \
> > +     _device_table)                                                  \
> > +     __attribute__ ((unused, alias(__stringify(name))))
> >   #endif
> >
> >   /* Version of form [<epoch>:]<version>[-<extra-version>].