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

[Laurent Pinchart]

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.

> +
>  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_)
		};

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