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From:   Arnd Bergmann <arnd@kernel.org>
Date:   Fri, 4 Dec 2020 13:49:39 +0100
Message-ID: <CAK8P3a0PzyP9L5zYvfTCmAtCSxZBBjg6Pzc6Ta91gWH_HXVmNw@mail.gmail.com>
Subject: Re: [PATCH] staging: bcm2835: fix vchiq_mmal dependencies
To:     Jacopo Mondi <jacopo@jmondi.org>
Cc:     driverdevel <devel@driverdev.osuosl.org>,
        Arnd Bergmann <arnd@arndb.de>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        bcm-kernel-feedback-list <bcm-kernel-feedback-list@broadcom.com>,
        Nicolas Saenz Julienne <nsaenzjulienne@suse.de>,
        Linux ARM <linux-arm-kernel@lists.infradead.org>,
        "moderated list:BROADCOM BCM2835 ARM ARCHITECTURE" 
        <linux-rpi-kernel@lists.infradead.org>
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On Fri, Dec 4, 2020 at 11:44 AM Jacopo Mondi <jacopo@jmondi.org> wrote:
>
> Hi Arnd,
>
> On Thu, Dec 03, 2020 at 11:38:30PM +0100, Arnd Bergmann wrote:
> > From: Arnd Bergmann <arnd@arndb.de>
> >
> > When the MMAL code is built-in but the vchiq core config is
> > set to =m, the mmal code never gets built, which in turn can
> > lead to link errors:
>
> My bad, I repetedly ignored the error report received from the 'kernel
> test robot' about this. Thanks for fixing.
>
> For my eduction, why would the vchiq-mmal code not get build if
> vchiq-core is set to M ? I mean, that configuration is indeed wrong,
> as vchiq-mmal uses symbols from vchiq-core and I would expect that to
> fail when building the kernel image, not have the other modules (as
> bcm2835-camera) fail as a consequence when building modules.


drivers/staging/Makefile has this line:

obj-$(CONFIG_BCM2835_VCHIQ)     += vc04_services/

when CONFIG_BCM2835_VCHIQ=m, the kbuild infrastructure
only enters the subdirectory while building modules, but a built-in
mmal driver is not a loadable module, so it does not get built
at that time. When compiling the built-in code, the subdirectory is
not entered.

> > Fixes: b18ee53ad297 ("staging: bcm2835: Break MMAL support out from camera")
> > Signed-off-by: Arnd Bergmann <arnd@arndb.de>
>
> Acked-by: Jacopo Mondi <jacopo@jmondi.org>
>
> If you noticed this from the same error notification I recevied it
> might be fair to report:
> Reported-by: kernel test robot <lkp@intel.com>

I had not seen that report but found it during my own testing,
thanks for adding.

      Arnd