[libcamera-devel] [PATCH v2 6/9] android: camera_device: Add a queue for sending capture results

[Umang Jain]

When a camera capture request completes, the next step is to send the
capture results to the framework via process_capture_results(). All
the capture associated result metadata is prepared and populated. If
any post-processing is required, it will also take place in the same
thread (which can be blocking for a subtaintial amount of time) before
the results can be sent back to the framework.

Subsequent patches will move the post-processing to run in a separate
thread. In order to do so, there is few bits of groundwork which this
patch entails. Mainly, we need to preserve the order of sending
the capture results back in which they were queued by the framework
to the HAL (i.e. the order is sequential). Hence, we need to add a queue
in which capture results can be queued with context.

As per this patch, the post-processor still runs synchronously as
before, but it will queue up the current capture results with context.
Later down the line, the capture results are dequeud in order and
sent back to the framework via sendQueuedCaptureResults(). If the queue
is empty or unused, the current behaviour is to skip the queue and
send capture results directly.

The context is preserved using Camera3RequestDescriptor utility
structure. It has been expanded accordingly to address the needs of
the functionality.
---
Check if we can drop unique_ptr to camera3descriptor
---

Signed-off-by: Umang Jain <umang.jain at ideasonboard.com>
---
 src/android/camera_device.cpp | 106 ++++++++++++++++++++++++++++++----
 src/android/camera_device.h   |  22 +++++++
 src/android/camera_stream.cpp |   2 +
 3 files changed, 119 insertions(+), 11 deletions(-)

diff --git a/src/android/camera_device.cpp b/src/android/camera_device.cpp
index 84549d04..7f04d225 100644
--- a/src/android/camera_device.cpp
+++ b/src/android/camera_device.cpp
@@ -240,6 +240,8 @@ Camera3RequestDescriptor::Camera3RequestDescriptor(
 	/* Clone the controls associated with the camera3 request. */
 	settings_ = CameraMetadata(camera3Request->settings);
 
+	internalBuffer_ = nullptr;
+
 	/*
 	 * Create the CaptureRequest, stored as a unique_ptr<> to tie its
 	 * lifetime to the descriptor.
@@ -989,6 +991,7 @@ int CameraDevice::processCaptureRequest(camera3_capture_request_t *camera3Reques
 			 * once it has been processed.
 			 */
 			buffer = cameraStream->getBuffer();
+			descriptor.internalBuffer_ = buffer;
 			LOG(HAL, Debug) << ss.str() << " (internal)";
 			break;
 		}
@@ -1148,26 +1151,107 @@ void CameraDevice::requestComplete(Request *request)
 			continue;
 		}
 
+
+		/*
+		 * Save the current context of capture result and queue the
+		 * descriptor before processing the camera stream.
+		 *
+		 * When the processing completes, the descriptor will be
+		 * dequeued and capture results will be sent to the framework.
+		 */
+		descriptor.status_ = Camera3RequestDescriptor::Pending;
+		descriptor.resultMetadata_ = std::move(resultMetadata);
+		descriptor.captureResult_ = captureResult;
+
+		std::unique_ptr<Camera3RequestDescriptor> reqDescriptor =
+			std::make_unique<Camera3RequestDescriptor>();
+		*reqDescriptor = std::move(descriptor);
+		queuedDescriptor_.push_back(std::move(reqDescriptor));
+
+		Camera3RequestDescriptor *currentDescriptor = queuedDescriptor_.back().get();
 		int ret = cameraStream->process(src, *buffer.buffer,
-						descriptor.settings_,
-						resultMetadata.get(),
-						&descriptor);
+						currentDescriptor->settings_,
+						currentDescriptor->resultMetadata_.get(),
+						currentDescriptor);
+		return;
+	}
+
+	if (queuedDescriptor_.empty()) {
+		captureResult.result = resultMetadata->get();
+		callbacks_->process_capture_result(callbacks_, &captureResult);
+	} else {
+		/*
+		 * Previous capture results waiting to be sent to framework
+		 * hence, queue the current capture results as well. After that,
+		 * check if any results are ready to be sent back to the
+		 * framework.
+		 */
+		descriptor.status_ = Camera3RequestDescriptor::Succeeded;
+		descriptor.resultMetadata_ = std::move(resultMetadata);
+		descriptor.captureResult_ = captureResult;
+		std::unique_ptr<Camera3RequestDescriptor> reqDescriptor =
+			std::make_unique<Camera3RequestDescriptor>();
+		*reqDescriptor = std::move(descriptor);
+		queuedDescriptor_.push_back(std::move(reqDescriptor));
+
+		sendQueuedCaptureResults();
+	}
+}
+
+void CameraDevice::streamProcessingComplete(CameraStream *cameraStream,
+					    CameraStream::ProcessStatus status,
+					    const Camera3RequestDescriptor *context)
+{
+	for (auto &d : queuedDescriptor_) {
+		if (d.get() != context)
+			continue;
+
 		/*
 		 * Return the FrameBuffer to the CameraStream now that we're
 		 * done processing it.
 		 */
 		if (cameraStream->type() == CameraStream::Type::Internal)
-			cameraStream->putBuffer(src);
-
-		if (ret) {
-			buffer.status = CAMERA3_BUFFER_STATUS_ERROR;
-			notifyError(descriptor.frameNumber_, buffer.stream,
-				    CAMERA3_MSG_ERROR_BUFFER);
+			cameraStream->putBuffer(d->internalBuffer_);
+
+		if (status == CameraStream::ProcessStatus::Succeeded) {
+			d->status_ = Camera3RequestDescriptor::Succeeded;
+		} else {
+			d->status_ = Camera3RequestDescriptor::Failed;
+
+			d->captureResult_.partial_result = 0;
+			for (camera3_stream_buffer_t &buffer : d->buffers_) {
+				CameraStream *cs = static_cast<CameraStream *>(buffer.stream->priv);
+
+				if (cs->camera3Stream().format != HAL_PIXEL_FORMAT_BLOB)
+					continue;
+				buffer.status = CAMERA3_BUFFER_STATUS_ERROR;
+				notifyError(d->frameNumber_, buffer.stream,
+					    CAMERA3_MSG_ERROR_BUFFER);
+			}
 		}
+		break;
 	}
 
-	captureResult.result = resultMetadata->get();
-	callbacks_->process_capture_result(callbacks_, &captureResult);
+	/*
+	 * Send back capture results to the framework by inspecting the queue.
+	 * The framework can defer queueing further requests to the HAL (via
+	 * process_capture_request) unless until it receives the capture results
+	 * for already queued requests.
+	 */
+	sendQueuedCaptureResults();
+}
+
+void CameraDevice::sendQueuedCaptureResults()
+{
+	while (!queuedDescriptor_.empty()) {
+		std::unique_ptr<Camera3RequestDescriptor> &d = queuedDescriptor_.front();
+		if (d->status_ == Camera3RequestDescriptor::Pending)
+			return;
+
+		d->captureResult_.result = d->resultMetadata_->get();
+		callbacks_->process_capture_result(callbacks_, &(d->captureResult_));
+		queuedDescriptor_.pop_front();
+	}
 }
 
 std::string CameraDevice::logPrefix() const
diff --git a/src/android/camera_device.h b/src/android/camera_device.h
index b59ac3e7..e7318358 100644
--- a/src/android/camera_device.h
+++ b/src/android/camera_device.h
@@ -7,6 +7,7 @@
 #ifndef __ANDROID_CAMERA_DEVICE_H__
 #define __ANDROID_CAMERA_DEVICE_H__
 
+#include <deque>
 #include <map>
 #include <memory>
 #include <mutex>
@@ -46,6 +47,20 @@ struct Camera3RequestDescriptor {
 	std::vector<std::unique_ptr<libcamera::FrameBuffer>> frameBuffers_;
 	CameraMetadata settings_;
 	std::unique_ptr<CaptureRequest> request_;
+
+	/*
+	 * Below are utility placeholders used when a capture result
+	 * needs to be queued before completion via process_capture_result()
+	 */
+	enum completionStatus {
+		Pending,
+		Succeeded,
+		Failed,
+	};
+	std::unique_ptr<CameraMetadata> resultMetadata_;
+	camera3_capture_result_t captureResult_;
+	libcamera::FrameBuffer *internalBuffer_;
+	completionStatus status_;
 };
 
 class CameraDevice : protected libcamera::Loggable
@@ -78,6 +93,9 @@ public:
 	int processCaptureRequest(camera3_capture_request_t *request);
 	void requestComplete(libcamera::Request *request);
 
+	void streamProcessingComplete(CameraStream *stream,
+				      CameraStream::ProcessStatus status,
+				      const Camera3RequestDescriptor *context);
 protected:
 	std::string logPrefix() const override;
 
@@ -106,6 +124,8 @@ private:
 	std::unique_ptr<CameraMetadata> getResultMetadata(
 		const Camera3RequestDescriptor &descriptor) const;
 
+	void sendQueuedCaptureResults();
+
 	unsigned int id_;
 	camera3_device_t camera3Device_;
 
@@ -126,6 +146,8 @@ private:
 	libcamera::Mutex descriptorsMutex_; /* Protects descriptors_. */
 	std::map<uint64_t, Camera3RequestDescriptor> descriptors_;
 
+	std::deque<std::unique_ptr<Camera3RequestDescriptor>> queuedDescriptor_;
+
 	std::string maker_;
 	std::string model_;
 
diff --git a/src/android/camera_stream.cpp b/src/android/camera_stream.cpp
index 996779c4..c7d874b2 100644
--- a/src/android/camera_stream.cpp
+++ b/src/android/camera_stream.cpp
@@ -134,6 +134,8 @@ void CameraStream::postProcessingComplete(PostProcessor::Status status,
 		processStatus = ProcessStatus::Succeeded;
 	else
 		processStatus = ProcessStatus::Failed;
+
+	cameraDevice_->streamProcessingComplete(this, processStatus, context);
 }
 
 FrameBuffer *CameraStream::getBuffer()
-- 
2.31.1