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From:   Geert Uytterhoeven <geert@linux-m68k.org>
Date:   Mon, 8 Feb 2021 09:52:22 +0100
Message-ID: <CAMuHMdXb99O9j0ji65=GqXOu1iArBgjhzYEGHmO_mM=ursDp9w@mail.gmail.com>
Subject: Re: linux-next: build warning after merge of the v4l-dvb tree
To:     Mauro Carvalho Chehab <mchehab@kernel.org>
Cc:     Stephen Rothwell <sfr@canb.auug.org.au>,
        Jacopo Mondi <jacopo+renesas@jmondi.org>,
        Sakari Ailus <sakari.ailus@linux.intel.com>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Linux Next Mailing List <linux-next@vger.kernel.org>
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Hi Mauro,

On Mon, Feb 8, 2021 at 9:49 AM Mauro Carvalho Chehab <mchehab@kernel.org> wrote:
> Em Mon, 8 Feb 2021 09:33:14 +0100
> Geert Uytterhoeven <geert@linux-m68k.org> escreveu:
> > On Mon, Feb 8, 2021 at 7:35 AM Mauro Carvalho Chehab <mchehab@kernel.org> wrote:
> > > Em Mon, 8 Feb 2021 11:32:08 +1100
> > > Stephen Rothwell <sfr@canb.auug.org.au> escreveu:
> > >
> > > > After merging the v4l-dvb tree, today's linux-next build (x86_64
> > > > allmodconfig) produced this warning:
> > > >
> > > > WARNING: modpost: drivers/media/i2c/rdacm21-camera_module: 'max9271_set_serial_link' exported twice. Previous export was in drivers/media/i2c/rdacm20-camera_module.ko
> > > > WARNING: modpost: drivers/media/i2c/rdacm21-camera_module: 'max9271_configure_i2c' exported twice. Previous export was in drivers/media/i2c/rdacm20-camera_module.ko
> > > > WARNING: modpost: drivers/media/i2c/rdacm21-camera_module: 'max9271_set_high_threshold' exported twice. Previous export was in drivers/media/i2c/rdacm20-camera_module.ko
> > > > WARNING: modpost: drivers/media/i2c/rdacm21-camera_module: 'max9271_configure_gmsl_link' exported twice. Previous export was in drivers/media/i2c/rdacm20-camera_module.ko
> > > > WARNING: modpost: drivers/media/i2c/rdacm21-camera_module: 'max9271_set_gpios' exported twice. Previous export was in drivers/media/i2c/rdacm20-camera_module.ko
> > > > WARNING: modpost: drivers/media/i2c/rdacm21-camera_module: 'max9271_clear_gpios' exported twice. Previous export was in drivers/media/i2c/rdacm20-camera_module.ko
> > > > WARNING: modpost: drivers/media/i2c/rdacm21-camera_module: 'max9271_enable_gpios' exported twice. Previous export was in drivers/media/i2c/rdacm20-camera_module.ko
> > > > WARNING: modpost: drivers/media/i2c/rdacm21-camera_module: 'max9271_disable_gpios' exported twice. Previous export was in drivers/media/i2c/rdacm20-camera_module.ko
> > > > WARNING: modpost: drivers/media/i2c/rdacm21-camera_module: 'max9271_verify_id' exported twice. Previous export was in drivers/media/i2c/rdacm20-camera_module.ko
> > > > WARNING: modpost: drivers/media/i2c/rdacm21-camera_module: 'max9271_set_address' exported twice. Previous export was in drivers/media/i2c/rdacm20-camera_module.ko
> > > > WARNING: modpost: drivers/media/i2c/rdacm21-camera_module: 'max9271_set_deserializer_address' exported twice. Previous export was in drivers/media/i2c/rdacm20-camera_module.ko
> > > > WARNING: modpost: drivers/media/i2c/rdacm21-camera_module: 'max9271_set_translation' exported twice. Previous export was in drivers/media/i2c/rdacm20-camera_module.ko
> > > >
> > > > Introduced by commit
> > > >
> > > >   a59f853b3b4b ("media: i2c: Add driver for RDACM21 camera module")
> > > >
> > >
> > > It sounds to be due to a Makefile mess:
> > >
> > >         drivers/media/i2c/Makefile:rdacm20-camera_module-objs   := rdacm20.o max9271.o
> > >         drivers/media/i2c/Makefile:rdacm21-camera_module-objs   := rdacm21.o max9271.o
> > >
> > > Neither drivers should be including max9271.o as their objects, but, instead,
> > > be addressing max9271 dependency via Kconfig.
> >
> > Wouldn't
> >
> >     obj-$(CONFIG_VIDEO_RDACM20)     += rdacm20.o max9271.o
> >     obj-$(CONFIG_VIDEO_RDACM21)     += rdacm21.o max9271.o
> >
> > work, too?
>
> Not 100% sure, but I guess this would cause problems with allyesconfig.

Duplicates will be filtered out.
An example using this method is drivers/net/ethernet/8390/Makefile.

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds