[libcamera-devel] [PATCH v3 3/3] libcamera: pipeline: raspberrypi: Update sensor's V4L2_CID_NOTIFY_GAINS control

[David Plowman]

Hi Laurent

Thanks for the review.

On Wed, 5 Jan 2022 at 19:47, Laurent Pinchart
<laurent.pinchart at ideasonboard.com> wrote:
>
> Hi David,
>
> Thank you for the patch.
>
> On Wed, Jan 05, 2022 at 03:55:39PM +0000, David Plowman wrote:
> > If the sensor exposes the V4L2_CID_NOTIFY_GAINS control, assume it
> > means the sensor wants to be told the latest colour gains.
> >
> > We store whether the control exists and if so its default value, to
> > save us checking for it on every frame.
> >
> > Signed-off-by: David Plowman <david.plowman at raspberrypi.com>
> > ---
> >  .../pipeline/raspberrypi/raspberrypi.cpp      | 31 +++++++++++++++++++
> >  1 file changed, 31 insertions(+)
> >
> > diff --git a/src/libcamera/pipeline/raspberrypi/raspberrypi.cpp b/src/libcamera/pipeline/raspberrypi/raspberrypi.cpp
> > index b5c687da..4adef952 100644
> > --- a/src/libcamera/pipeline/raspberrypi/raspberrypi.cpp
> > +++ b/src/libcamera/pipeline/raspberrypi/raspberrypi.cpp
> > @@ -264,6 +264,12 @@ public:
> >
> >       unsigned int dropFrameCount_;
> >
> > +     /*
> > +      * If set, this stores the value that represets a gain of one for
> > +      * the V4L2_CID_NOTIFY_GAINS control.
> > +      */
> > +     std::optional<int32_t> notifyGainsUnity_;
>
> A plain int32_t would be enough, as a zero value isn't valid. Up to
> you.

And I was trying so hard to avoid using the value 0 to have a
"special" meaning... :)

I think at this point I'm inclined to leave it as it is, unless anyone
else objects, or I might change it if I need to do another revision.

>
> > +
> >  private:
> >       void checkRequestCompleted();
> >       void fillRequestMetadata(const ControlList &bufferControls,
> > @@ -1191,6 +1197,15 @@ int PipelineHandlerRPi::registerCamera(MediaDevice *unicam, MediaDevice *isp)
> >       /* Initialize the camera properties. */
> >       data->properties_ = data->sensor_->properties();
> >
> > +     /*
> > +      * The V4L2_CID_NOTIFY_GAINS control, if present, is used to inform the
> > +      * sensor of the colour gains. It is defined to be a linear gain where
> > +      * the default value represents a gain of exactly one.
> > +      */
> > +     auto it = data->sensor_->controls().find(V4L2_CID_NOTIFY_GAINS);
> > +     if (it != data->sensor_->controls().end())
> > +             data->notifyGainsUnity_ = it->second.def().get<int32_t>();
> > +
> >       /*
> >        * Set a default value for the ScalerCropMaximum property to show
> >        * that we support its use, however, initialise it to zero because
> > @@ -1495,6 +1510,22 @@ void RPiCameraData::statsMetadataComplete(uint32_t bufferId, const ControlList &
> >       Request *request = requestQueue_.front();
> >       request->metadata().merge(controls);
> >
> > +     /*
> > +      * Inform the sensor of the latest colour gains if it has the
> > +      * V4L2_CID_NOTIFY_GAINS control (which means notifyGainsUnity_ is set).
> > +      */
> > +     if (notifyGainsUnity_ && controls.contains(libcamera::controls::ColourGains)) {
> > +             libcamera::Span<const float> colourGains = controls.get(libcamera::controls::ColourGains);
> > +             /* The control wants linear gains in the order B, Gb, Gr, R. */
> > +             ControlList ctrls(sensor_->controls());
> > +             std::array<int32_t, 4> gains = { static_cast<int32_t>(colourGains[1] * *notifyGainsUnity_),
> > +                                              *notifyGainsUnity_, *notifyGainsUnity_,
> > +                                              static_cast<int32_t>(colourGains[0] * *notifyGainsUnity_) };
>
> Let's shorten the lines a bit:
>
>                 std::array<int32_t, 4> gains{
>                         static_cast<int32_t>(colourGains[1] * *notifyGainsUnity_),
>                         *notifyGainsUnity_,
>                         *notifyGainsUnity_,
>                         static_cast<int32_t>(colourGains[0] * *notifyGainsUnity_)
>                 };

Is that fix-while-applying-able, do you think? Otherwise I'll do
another version.

Thanks again!
David

>
> Reviewed-by: Laurent Pinchart <laurent.pinchart at ideasonboard.com>
>
> > +             ctrls.set(V4L2_CID_NOTIFY_GAINS, Span<const int32_t>{ gains });
> > +
> > +             sensor_->setControls(&ctrls);
> > +     }
> > +
> >       state_ = State::IpaComplete;
> > +             ctrls.set(V4L2_CID_NOTIFY_GAINS, Span<const int32_t>{ gains });
> > +
> > +             sensor_->setControls(&ctrls);
> > +     }
> > +
> >       state_ = State::IpaComplete;
> >       handleState();
> >  }
>
> --
> Regards,
>
> Laurent Pinchart