linux-kernel - Re: [PATCH] staging: bcm2835-camera: Avoid unneeded internal declaration warning

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Date:   Fri, 28 Sep 2018 07:48:56 -0700
From:   Nathan Chancellor <natechancellor@...il.com>
To:     Dave Stevenson <dave.stevenson@...pberrypi.org>
Cc:     Eric Anholt <eric@...olt.net>,
        Stefan Wahren <stefan.wahren@...e.com>,
        Greg KH <gregkh@...uxfoundation.org>,
        devel@...verdev.osuosl.org, ndesaulniers@...gle.com,
        linux-kernel@...r.kernel.org,
        "moderated list:BROADCOM BCM2835 ARM ARCHITECTURE" 
        <linux-rpi-kernel@...ts.infradead.org>,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH] staging: bcm2835-camera: Avoid unneeded internal
 declaration warning

On Fri, Sep 28, 2018 at 10:04:29AM +0100, Dave Stevenson wrote:
> Hi Nate
> 
> Thanks for the patch.
> 
> On Fri, 28 Sep 2018 at 01:53, Nathan Chancellor
> <natechancellor@...il.com> wrote:
> >
> > Clang warns:
> >
> > drivers/staging/vc04_services/bcm2835-camera/controls.c:59:18: warning:
> > variable 'mains_freq_qmenu' is not needed and will not be emitted
> > [-Wunneeded-internal-declaration]
> > static const s64 mains_freq_qmenu[] = {
> >                  ^
> > 1 warning generated.
> >
> > This is because mains_freq_qmenu is currently only used in an ARRAY_SIZE
> > macro, which is a compile time evaluation in this case. Avoid this by
> > adding mains_freq_qmenu as the imenu member of this structure, which
> > matches all other controls that uses the ARRAY_SIZE macro in v4l2_ctrls.
> > This turns out to be a no-op because V4L2_CID_MPEG_VIDEO_BITRATE_MODE is
> > defined as a MMAL_CONTROL_TYPE_STD_MENU, which does not pass the imenu
> > definition along to v4l2_ctrl_new in bm2835_mmal_init_controls.
> 
> There's a slight confusion betwen V4L2_CID_MPEG_VIDEO_BITRATE_MODE and
> V4L2_CID_POWER_LINE_FREQUENCY in your description.
> 
> However you're right that MMAL_CONTROL_TYPE_STD_MENU calls
> v4l2_ctrl_new_std_menu which doesn't need a menu array (it's
> v4l2_ctrl_new_int_menu that does). That means the correct fix is to
> define the max value using the relevant enum (in this case
> V4L2_CID_POWER_LINE_FREQUENCY_AUTO) and remove the array.
> 
> The same is true for V4L2_CID_MPEG_VIDEO_BITRATE_MODE - max should be
> V4L2_MPEG_VIDEO_BITRATE_MODE_CBR, and remove the bitrate_mode_qmenu
> array.
> 
> Thanks,
>   Dave
> 

Hi Dave,

Thank you for the review, I appreciate it. I had certainly considered
that solution first butnfigured this was the more conservative change.

I will send a v2 soon with the suggested change.

Nathan

> > Link: https://github.com/ClangBuiltLinux/linux/issues/122
> > Signed-off-by: Nathan Chancellor <natechancellor@...il.com>
> > ---
> >  drivers/staging/vc04_services/bcm2835-camera/controls.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/drivers/staging/vc04_services/bcm2835-camera/controls.c b/drivers/staging/vc04_services/bcm2835-camera/controls.c
> > index cff7b1e07153..a2c55cb2192a 100644
> > --- a/drivers/staging/vc04_services/bcm2835-camera/controls.c
> > +++ b/drivers/staging/vc04_services/bcm2835-camera/controls.c
> > @@ -1106,7 +1106,7 @@ static const struct bm2835_mmal_v4l2_ctrl v4l2_ctrls[V4L2_CTRL_COUNT] = {
> >         {
> >                 V4L2_CID_POWER_LINE_FREQUENCY, MMAL_CONTROL_TYPE_STD_MENU,
> >                 0, ARRAY_SIZE(mains_freq_qmenu) - 1,
> > -               1, 1, NULL,
> > +               1, 1, mains_freq_qmenu,
> >                 MMAL_PARAMETER_FLICKER_AVOID,
> >                 &ctrl_set_flicker_avoidance,
> >                 false
> > --
> > 2.19.0
> >
> >
> > _______________________________________________
> > linux-rpi-kernel mailing list
> > linux-rpi-kernel@...ts.infradead.org
> > http://lists.infradead.org/mailman/listinfo/linux-rpi-kernel

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