linux-kernel - Re: [PATCH] staging: bcm2835-camera: remove extraneous setting of dev->colourfx.enable

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Date:   Mon, 8 Oct 2018 19:09:07 +0200 (CEST)
From:   Stefan Wahren <stefan.wahren@...e.com>
To:     Dave Stevenson <dave.stevenson@...pberrypi.org>
Cc:     colin.king@...onical.com, Eric Anholt <eric@...olt.net>,
        Greg KH <gregkh@...uxfoundation.org>,
        bcm-kernel-feedback-list@...adcom.com,
        "moderated list:BROADCOM BCM2835 ARM ARCHITECTURE" 
        <linux-rpi-kernel@...ts.infradead.org>,
        linux-arm-kernel@...ts.infradead.org, devel@...verdev.osuosl.org,
        kernel-janitors@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] staging: bcm2835-camera: remove extraneous setting of
 dev->colourfx.enable

Hi Dave,

> Dave Stevenson <dave.stevenson@...pberrypi.org> hat am 8. Oktober 2018 um 18:51 geschrieben:
> 
> 
>  Hi Stefan.
> 
> Thanks for forwarding as the linux-rpi-kernel list hasn't sent it to me as yet.

AFAIK every mail with more than 5 recipients will be delayed.

> 
> On Mon, 8 Oct 2018 at 16:48, Stefan Wahren <stefan.wahren@...e.com> wrote:
> >
> > Hi Colin,
> >
> > Am 08.10.2018 um 16:50 schrieb Colin King:
> > > From: Colin Ian King <colin.king@...onical.com>
> > >
> > > Currently dev->colourfx.enable is being set twice, hence the first
> > > occurrance is redundant and can be removed, so remove it. This minor
> > > issue was introduced by commit 7b3ad5abf027 ("staging: Import the
> > > BCM2835 MMAL-based V4L2 camera driver.").
> > >
> > > Detected by CoverityScan CID#1419711 ("Unused value")
> > >
> > > Signed-off-by: Colin Ian King <colin.king@...onical.com>
> > > ---
> > >  drivers/staging/vc04_services/bcm2835-camera/controls.c | 1 -
> > >  1 file changed, 1 deletion(-)
> > >
> > > diff --git a/drivers/staging/vc04_services/bcm2835-camera/controls.c b/drivers/staging/vc04_services/bcm2835-camera/controls.c
> > > index a2c55cb2192a..99831dd4365d 100644
> > > --- a/drivers/staging/vc04_services/bcm2835-camera/controls.c
> > > +++ b/drivers/staging/vc04_services/bcm2835-camera/controls.c
> > > @@ -588,7 +588,6 @@ static int ctrl_set_colfx(struct bm2835_mmal_dev *dev,
> > >
> > >       control = &dev->component[MMAL_COMPONENT_CAMERA]->control;
> > >
> > > -     dev->colourfx.enable = (ctrl->val & 0xff00) >> 8;
> > >       dev->colourfx.enable = ctrl->val & 0xff;
> > >
> > >       ret = vchiq_mmal_port_parameter_set(dev->instance, control,
> >
> > as long as the current behavior is correct, i'm okay with this patch.
> > But the byte masking looks suspicious, so i hope Dave can clarify that.
> 
> It's writing to the wrong structure member.
> The function is used on the V4L2 control V4L2_CID_COLORFX_CBCR, which
> is defined as:
> V4L2_CID_COLORFX_CBCR (integer)
> Determines the Cb and Cr coefficients for V4L2_COLORFX_SET_CBCR color
> effect. Bits [7:0] of the supplied 32 bit value are interpreted as Cr
> component, bits [15:8] as Cb component and bits [31:16] must be zero.
> 
> ctrl->val should therefore be setting dev->colourfx.u and
> dev->colourfx.v with those masks. dev->colourfx.enable field should
> have been set when going through ctrl_set_image_effect for contol
> V4L2_CID_COLORFX set to V4L2_COLORFX_SET_CBCR.
> 
> I've confirmed with qv4l2 that that is what is wrong. That's only been
> lurking there for almost 5 years - shows how often these weirder
> effects get used.
> I don't mind whether Colin's patch gets merged and then fixed up, or
> drop Colin's patch and apply the correct logic via a new patch.

no this patch shouldn't be applied. Does it mean you want to send the proper one?

> 
>   Dave