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

[Stanislaw Gruszka]

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.

Bug: https://bugs.libcamera.org/show_bug.cgi?id=241
Signed-off-by: Stanislaw Gruszka <stanislaw.gruszka at linux.intel.com>
---
 src/libcamera/pipeline/simple/simple.cpp | 26 ++++++++++++++++++++++--
 1 file changed, 24 insertions(+), 2 deletions(-)

diff --git a/src/libcamera/pipeline/simple/simple.cpp b/src/libcamera/pipeline/simple/simple.cpp
index 8ac24e6e..52f3d520 100644
--- a/src/libcamera/pipeline/simple/simple.cpp
+++ b/src/libcamera/pipeline/simple/simple.cpp
@@ -382,6 +382,7 @@ private:
 	std::map<const MediaEntity *, EntityData> entities_;
 
 	MediaDevice *converter_;
+	V4L2Subdevice *eventEmitter_;
 	bool swIspEnabled_;
 };
 
@@ -1299,8 +1300,6 @@ 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;
@@ -1368,6 +1367,23 @@ int SimplePipelineHandler::start(Camera *camera, [[maybe_unused]] const ControlL
 
 	video->bufferReady.connect(data, &SimpleCameraData::imageBufferReady);
 
+	/*
+	 * Enable frame start event on last device in the pipeline
+	 * that provides the events.
+	 */
+	for (auto it = data->entities_.rbegin(); it != data->entities_.rend(); ++it) {
+		V4L2Subdevice *sd = subdev(it->entity);
+		if (!sd)
+			continue;
+		if (sd->setFrameStartEnabled(true) < 0)
+			continue;
+
+		sd->frameStart.connect(data->delayedCtrls_.get(),
+				       &DelayedControls::applyControls);
+		eventEmitter_ = sd;
+		break;
+	}
+
 	ret = video->streamOn();
 	if (ret < 0) {
 		stop(camera);
@@ -1400,6 +1416,12 @@ void SimplePipelineHandler::stopDevice(Camera *camera)
 	SimpleCameraData *data = cameraData(camera);
 	V4L2VideoDevice *video = data->video_;
 
+	if (eventEmitter_) {
+		eventEmitter_->setFrameStartEnabled(false);
+		eventEmitter_->frameStart.disconnect(data->delayedCtrls_.get(),
+						     &DelayedControls::applyControls);
+	}
+
 	if (data->useConversion_) {
 		if (data->converter_)
 			data->converter_->stop();
-- 
2.43.0