[PATCH v3 2/2] pipeline: simple: Use proper device for frame start events

[Kieran Bingham]

Quoting Stanislaw Gruszka (2025-02-18 09:19:51)
> 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.
> 
> Without DelayedConntrols:applyControls() is possible that we can get
> call to DelayedControls::get() with frame number that exceed number
> of saved entries and get below assertion failure:
> 
> ../src/libcamera/delayed_controls.cpp:227:
> libcamera::ControlList libcamera::DelayedControls::get(uint32_t):
> Assertion `info.type() != ControlTypeNone' failed
> 
> Assertion failure can happen at the beginning of streaming when
> ControlRingBuffer is not yet filled and there are errors on CSI-2.
> 
> To fix, loop over devices in the pipeline (starting from the last one),
> find one that emits start frame events and connect applyControls()
> to it. Additionally remove direct call to sensor_->setControls() if
> the emitter device was found.
> 
> Bug: https://bugs.libcamera.org/show_bug.cgi?id=241
> Co-developed-by: Hans de Goede <hdegoede at redhat.com>
> Signed-off-by: Hans de Goede <hdegoede at redhat.com>
> Reviewed-by: Hans de Goede <hdegoede at redhat.com> # v2
> Tested-by: Hans de Goede <hdegoede at redhat.com> # Lenovo X1 Yoga IPU6 + ov2740 # v2
> Reviewed-by: Milan Zamazal <mzamazal at redhat.com> # v2
> Signed-off-by: Stanislaw Gruszka <stanislaw.gruszka at linux.intel.com>

This still fixes the flicker on X13s

Tested-by: Kieran Bingham <kieran.bingham at ideasonboard.com> # Lenovo X13s

But I'm getting segfaults on stopping the camera. I think that's
unrelated to this patch - and exists on mainline so :


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


> ---
>  src/libcamera/pipeline/simple/simple.cpp | 40 +++++++++++++++++++++---
>  1 file changed, 36 insertions(+), 4 deletions(-)
> 
> diff --git a/src/libcamera/pipeline/simple/simple.cpp b/src/libcamera/pipeline/simple/simple.cpp
> index 6e039bf3..ad2167dc 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 *eventEmitter_;
> 
>         std::vector<Configuration> configs_;
>         std::map<PixelFormat, std::vector<const Configuration *>> formats_;
> @@ -579,6 +580,19 @@ int SimpleCameraData::init()
> 
>         properties_ = sensor_->properties();
> 
> +       eventEmitter_ = nullptr;
> +       for (auto it = entities_.rbegin(); it != entities_.rend(); ++it) {
> +               V4L2Subdevice *sd = pipe->subdev(it->entity);
> +               if (!sd || !sd->supportsFrameStartEvent())
> +                       continue;
> +
> +               LOG(SimplePipeline, Debug)
> +                       << "Using " << it->entity->name() << " frameStart signal";
> +
> +               eventEmitter_ = sd;
> +               break;
> +       }
> +
>         return 0;
>  }
> 
> @@ -897,8 +911,11 @@ void SimpleCameraData::ispStatsReady(uint32_t frame, uint32_t bufferId)
>  void SimpleCameraData::setSensorControls(const ControlList &sensorControls)
>  {
>         delayedCtrls_->push(sensorControls);
> -       ControlList ctrls(sensorControls);
> -       sensor_->setControls(&ctrls);
> +       /* Directly apply controls now if there is no frameStart signal */
> +       if (!eventEmitter_ || !eventEmitter_->frameStartEnabled()) {
> +               ControlList ctrls(sensorControls);
> +               sensor_->setControls(&ctrls);
> +       }
>  }
> 
>  /* Retrieve all source pads connected to a sink pad through active routes. */
> @@ -1285,8 +1302,6 @@ 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);
> 
>         StreamConfiguration inputCfg;
>         inputCfg.pixelFormat = pipeConfig->captureFormat;
> @@ -1325,6 +1340,7 @@ int SimplePipelineHandler::start(Camera *camera, [[maybe_unused]] const ControlL
>  {
>         SimpleCameraData *data = cameraData(camera);
>         V4L2VideoDevice *video = data->video_;
> +       V4L2Subdevice *eventEmitter = data->eventEmitter_;
>         int ret;
> 
>         const MediaPad *pad = acquirePipeline(data);
> @@ -1354,6 +1370,15 @@ int SimplePipelineHandler::start(Camera *camera, [[maybe_unused]] const ControlL
> 
>         video->bufferReady.connect(data, &SimpleCameraData::imageBufferReady);
> 
> +       if (eventEmitter) {
> +               ret = eventEmitter->setFrameStartEnabled(true);
> +               if (ret == 0)
> +                       eventEmitter->frameStart.connect(data->delayedCtrls_.get(),
> +                                                        &DelayedControls::applyControls);
> +       }
> +
> +       data->delayedCtrls_->reset();
> +
>         ret = video->streamOn();
>         if (ret < 0) {
>                 stop(camera);
> @@ -1385,6 +1410,13 @@ void SimplePipelineHandler::stopDevice(Camera *camera)
>  {
>         SimpleCameraData *data = cameraData(camera);
>         V4L2VideoDevice *video = data->video_;
> +       V4L2Subdevice *eventEmitter = data->eventEmitter_;
> +
> +       if (eventEmitter) {
> +               eventEmitter->setFrameStartEnabled(false);
> +               eventEmitter->frameStart.disconnect(data->delayedCtrls_.get(),
> +                                                   &DelayedControls::applyControls);
> +       }
> 
>         if (data->useConversion_) {
>                 if (data->converter_)
> --
> 2.43.0
>