[PATCH v5 2/5] pipeline: simple: Use proper device for frame start events

[Kieran Bingham]

Quoting Stanislaw Gruszka (2025-02-25 16:41:13)
> Currently we use frame start event from video capture device to
> apply controls. But the capture device might not generate the events.
> Usually CSI-2 receiver is proper device to subscribe for start
> frame events.
> 
> To fix, loop over devices in the pipeline to find the one that
> supports events and use it as start frame emitter.
> 
> Co-developed-by: Hans de Goede <hdegoede at redhat.com>
> Signed-off-by: Hans de Goede <hdegoede at redhat.com>
> Signed-off-by: Stanislaw Gruszka <stanislaw.gruszka at linux.intel.com>

This is something that I should incorporate into the MediaPipeline (or
CameraPipeline, or Pipeline?) class I have worked on to generalise
camera pipes...

But I think it's helpful here now.


Reviewed-by: Kieran Bingham <kieran.bingham at ideasonboard.com>

> ---
>  src/libcamera/pipeline/simple/simple.cpp | 20 ++++++++++++++++++--
>  1 file changed, 18 insertions(+), 2 deletions(-)
> 
> diff --git a/src/libcamera/pipeline/simple/simple.cpp b/src/libcamera/pipeline/simple/simple.cpp
> index 6e039bf3..063a098f 100644
> --- a/src/libcamera/pipeline/simple/simple.cpp
> +++ b/src/libcamera/pipeline/simple/simple.cpp
> @@ -277,6 +277,7 @@ public:
>         std::list<Entity> entities_;
>         std::unique_ptr<CameraSensor> sensor_;
>         V4L2VideoDevice *video_;
> +       V4L2Subdevice *frameStartEmitter_;
>  
>         std::vector<Configuration> configs_;
>         std::map<PixelFormat, std::vector<const Configuration *>> formats_;
> @@ -579,6 +580,19 @@ int SimpleCameraData::init()
>  
>         properties_ = sensor_->properties();
>  
> +       frameStartEmitter_ = nullptr;
> +       for (const Entity &entity : entities_) {
> +               V4L2Subdevice *sd = pipe->subdev(entity.entity);
> +               if (!sd || !sd->supportsFrameStartEvent())
> +                       continue;
> +
> +               LOG(SimplePipeline, Debug)
> +                       << "Using " << entity.entity->name() << " frameStart signal";
> +
> +               frameStartEmitter_ = sd;
> +               break;
> +       }
> +
>         return 0;
>  }
>  
> @@ -1215,6 +1229,7 @@ int SimplePipelineHandler::configure(Camera *camera, CameraConfiguration *c)
>                 static_cast<SimpleCameraConfiguration *>(c);
>         SimpleCameraData *data = cameraData(camera);
>         V4L2VideoDevice *video = data->video_;
> +       V4L2Subdevice *frameStartEmitter = data->frameStartEmitter_;
>         int ret;
>  
>         /*
> @@ -1285,8 +1300,9 @@ int SimplePipelineHandler::configure(Camera *camera, CameraConfiguration *c)
>         data->delayedCtrls_ =
>                 std::make_unique<DelayedControls>(data->sensor_->device(),
>                                                   params);
> -       data->video_->frameStart.connect(data->delayedCtrls_.get(),
> -                                        &DelayedControls::applyControls);
> +       if (frameStartEmitter)
> +               frameStartEmitter->frameStart.connect(data->delayedCtrls_.get(),
> +                                                     &DelayedControls::applyControls);
>  
>         StreamConfiguration inputCfg;
>         inputCfg.pixelFormat = pipeConfig->captureFormat;
> -- 
> 2.43.0
>