[libcamera-devel,v4,2/4] android: camera_device: Transform descriptors_ map to queue
diff mbox series

Message ID 20210929133030.401961-3-umang.jain@ideasonboard.com
State Accepted
Delegated to: Umang Jain
Headers show
Series
  • Camera3RequestDescriptors std::map => std::queue
Related show

Commit Message

Umang Jain Sept. 29, 2021, 1:30 p.m. UTC 
The descriptors_ map holds Camera3RequestDescriptor(s) which are
per-capture requests placed by the framework to libcamera HAL.
CameraDevice::requestComplete() looks for the descriptor for which the
camera request has been completed and removes it from the map.
Since the requests are placed in form of FIFO and the framework expects
the order of completion to be FIFO as well, this calls for a need of
a queue rather than a std::map.

This patch still keeps the same lifetime of Camera3RequestDescriptor as
before i.e. in the requestComplete(). Previously, a descriptor was
extracted from the map and its lifetime was bound to requestComplete().
The lifetime is kept same by manually calling .pop_front() on the
queue. In the subsequent commit, this is likely to change with a
centralized location of dropping descriptors from the queue for request
completion.

Signed-off-by: Umang Jain <umang.jain@ideasonboard.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
---
 src/android/camera_device.cpp | 93 +++++++++++++++++++----------------
 src/android/camera_device.h   |  3 +-
 2 files changed, 53 insertions(+), 43 deletions(-)

Comments

Jacopo Mondi Sept. 29, 2021, 6:40 p.m. UTC | #1 
Hi Umang,

On Wed, Sep 29, 2021 at 07:00:28PM +0530, Umang Jain wrote:
> The descriptors_ map holds Camera3RequestDescriptor(s) which are
> per-capture requests placed by the framework to libcamera HAL.
> CameraDevice::requestComplete() looks for the descriptor for which the
> camera request has been completed and removes it from the map.
> Since the requests are placed in form of FIFO and the framework expects
> the order of completion to be FIFO as well, this calls for a need of
> a queue rather than a std::map.
>
> This patch still keeps the same lifetime of Camera3RequestDescriptor as
> before i.e. in the requestComplete(). Previously, a descriptor was
> extracted from the map and its lifetime was bound to requestComplete().
> The lifetime is kept same by manually calling .pop_front() on the

is kept the same

> queue. In the subsequent commit, this is likely to change with a
> centralized location of dropping descriptors from the queue for request
> completion.
>
> Signed-off-by: Umang Jain <umang.jain@ideasonboard.com>
> Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

Reviewed-by: Jacopo Mondi <jacopo@jmondi.org>

Thanks
   j

> ---
>  src/android/camera_device.cpp | 93 +++++++++++++++++++----------------
>  src/android/camera_device.h   |  3 +-
>  2 files changed, 53 insertions(+), 43 deletions(-)
>
> diff --git a/src/android/camera_device.cpp b/src/android/camera_device.cpp
> index 9287ea07..e815f7a0 100644
> --- a/src/android/camera_device.cpp
> +++ b/src/android/camera_device.cpp
> @@ -457,7 +457,8 @@ void CameraDevice::stop()
>  	worker_.stop();
>  	camera_->stop();
>
> -	descriptors_.clear();
> +	descriptors_ = {};
> +
>  	state_ = State::Stopped;
>  }
>
> @@ -955,7 +956,8 @@ int CameraDevice::processCaptureRequest(camera3_capture_request_t *camera3Reques
>  	 * The descriptor and the associated memory reserved here are freed
>  	 * at request complete time.
>  	 */
> -	Camera3RequestDescriptor descriptor(camera_.get(), camera3Request);
> +	auto descriptor = std::make_unique<Camera3RequestDescriptor>(camera_.get(),
> +								     camera3Request);
>
>  	/*
>  	 * \todo The Android request model is incremental, settings passed in
> @@ -966,12 +968,12 @@ int CameraDevice::processCaptureRequest(camera3_capture_request_t *camera3Reques
>  	if (camera3Request->settings)
>  		lastSettings_ = camera3Request->settings;
>  	else
> -		descriptor.settings_ = lastSettings_;
> +		descriptor->settings_ = lastSettings_;
> +
> +	LOG(HAL, Debug) << "Queueing request " << descriptor->request_->cookie()
> +			<< " with " << descriptor->buffers_.size() << " streams";
>
> -	LOG(HAL, Debug) << "Queueing request " << descriptor.request_->cookie()
> -			<< " with " << descriptor.buffers_.size() << " streams";
> -	for (unsigned int i = 0; i < descriptor.buffers_.size(); ++i) {
> -		const camera3_stream_buffer_t &camera3Buffer = descriptor.buffers_[i];
> +	for (const auto &[i, camera3Buffer] : utils::enumerate(descriptor->buffers_)) {
>  		camera3_stream *camera3Stream = camera3Buffer.stream;
>  		CameraStream *cameraStream = static_cast<CameraStream *>(camera3Stream->priv);
>
> @@ -1007,12 +1009,12 @@ int CameraDevice::processCaptureRequest(camera3_capture_request_t *camera3Reques
>  			 * associate it with the Camera3RequestDescriptor for
>  			 * lifetime management only.
>  			 */
> -			descriptor.frameBuffers_.push_back(
> +			descriptor->frameBuffers_.push_back(
>  				createFrameBuffer(*camera3Buffer.buffer,
>  						  cameraStream->configuration().pixelFormat,
>  						  cameraStream->configuration().size));
>
> -			buffer = descriptor.frameBuffers_.back().get();
> +			buffer = descriptor->frameBuffers_.back().get();
>  			acquireFence = camera3Buffer.acquire_fence;
>  			LOG(HAL, Debug) << ss.str() << " (direct)";
>  			break;
> @@ -1035,7 +1037,7 @@ int CameraDevice::processCaptureRequest(camera3_capture_request_t *camera3Reques
>  			return -ENOMEM;
>  		}
>
> -		descriptor.request_->addBuffer(cameraStream->stream(), buffer,
> +		descriptor->request_->addBuffer(cameraStream->stream(), buffer,
>  					       acquireFence);
>  	}
>
> @@ -1043,7 +1045,7 @@ int CameraDevice::processCaptureRequest(camera3_capture_request_t *camera3Reques
>  	 * Translate controls from Android to libcamera and queue the request
>  	 * to the CameraWorker thread.
>  	 */
> -	int ret = processControls(&descriptor);
> +	int ret = processControls(descriptor.get());
>  	if (ret)
>  		return ret;
>
> @@ -1071,11 +1073,11 @@ int CameraDevice::processCaptureRequest(camera3_capture_request_t *camera3Reques
>  		state_ = State::Running;
>  	}
>
> -	CaptureRequest *request = descriptor.request_.get();
> +	CaptureRequest *request = descriptor->request_.get();
>
>  	{
>  		MutexLocker descriptorsLock(descriptorsMutex_);
> -		descriptors_[descriptor.request_->cookie()] = std::move(descriptor);
> +		descriptors_.push(std::move(descriptor));
>  	}
>
>  	worker_.queueRequest(request);
> @@ -1085,26 +1087,28 @@ int CameraDevice::processCaptureRequest(camera3_capture_request_t *camera3Reques
>
>  void CameraDevice::requestComplete(Request *request)
>  {
> -	decltype(descriptors_)::node_type node;
> +	Camera3RequestDescriptor *descriptor;
>  	{
>  		MutexLocker descriptorsLock(descriptorsMutex_);
> -		auto it = descriptors_.find(request->cookie());
> -		if (it == descriptors_.end()) {
> -			/*
> -			 * \todo Clarify if the Camera has to be closed on
> -			 * ERROR_DEVICE and possibly demote the Fatal to simple
> -			 * Error.
> -			 */
> -			notifyError(0, nullptr, CAMERA3_MSG_ERROR_DEVICE);
> -			LOG(HAL, Fatal)
> -				<< "Unknown request: " << request->cookie();
> +		ASSERT(!descriptors_.empty());
> +		descriptor = descriptors_.front().get();
> +	}
>
> -			return;
> -		}
> +	if (descriptor->request_->cookie() != request->cookie()) {
> +		/*
> +		 * \todo Clarify if the Camera has to be closed on
> +		 * ERROR_DEVICE and possibly demote the Fatal to simple
> +		 * Error.
> +		 */
> +		notifyError(0, nullptr, CAMERA3_MSG_ERROR_DEVICE);
> +		LOG(HAL, Fatal)
> +			<< "Out-of-order completion for request "
> +			<< utils::hex(request->cookie());
>
> -		node = descriptors_.extract(it);
> +		MutexLocker descriptorsLock(descriptorsMutex_);
> +		descriptors_.pop();
> +		return;
>  	}
> -	Camera3RequestDescriptor &descriptor = node.mapped();
>
>  	/*
>  	 * Prepare the capture result for the Android camera stack.
> @@ -1113,9 +1117,9 @@ void CameraDevice::requestComplete(Request *request)
>  	 * post-processing/compression fails.
>  	 */
>  	camera3_capture_result_t captureResult = {};
> -	captureResult.frame_number = descriptor.frameNumber_;
> -	captureResult.num_output_buffers = descriptor.buffers_.size();
> -	for (camera3_stream_buffer_t &buffer : descriptor.buffers_) {
> +	captureResult.frame_number = descriptor->frameNumber_;
> +	captureResult.num_output_buffers = descriptor->buffers_.size();
> +	for (camera3_stream_buffer_t &buffer : descriptor->buffers_) {
>  		CameraStream *cameraStream =
>  			static_cast<CameraStream *>(buffer.stream->priv);
>
> @@ -1135,7 +1139,7 @@ void CameraDevice::requestComplete(Request *request)
>  		buffer.release_fence = -1;
>  		buffer.status = CAMERA3_BUFFER_STATUS_OK;
>  	}
> -	captureResult.output_buffers = descriptor.buffers_.data();
> +	captureResult.output_buffers = descriptor->buffers_.data();
>  	captureResult.partial_result = 1;
>
>  	/*
> @@ -1147,11 +1151,11 @@ void CameraDevice::requestComplete(Request *request)
>  				<< " not successfully completed: "
>  				<< request->status();
>
> -		notifyError(descriptor.frameNumber_, nullptr,
> +		notifyError(descriptor->frameNumber_, nullptr,
>  			    CAMERA3_MSG_ERROR_REQUEST);
>
>  		captureResult.partial_result = 0;
> -		for (camera3_stream_buffer_t &buffer : descriptor.buffers_) {
> +		for (camera3_stream_buffer_t &buffer : descriptor->buffers_) {
>  			/*
>  			 * Signal to the framework it has to handle fences that
>  			 * have not been waited on by setting the release fence
> @@ -1164,6 +1168,8 @@ void CameraDevice::requestComplete(Request *request)
>
>  		callbacks_->process_capture_result(callbacks_, &captureResult);
>
> +		MutexLocker descriptorsLock(descriptorsMutex_);
> +		descriptors_.pop();
>  		return;
>  	}
>
> @@ -1175,10 +1181,10 @@ void CameraDevice::requestComplete(Request *request)
>  	 */
>  	uint64_t sensorTimestamp = static_cast<uint64_t>(request->metadata()
>  							 .get(controls::SensorTimestamp));
> -	notifyShutter(descriptor.frameNumber_, sensorTimestamp);
> +	notifyShutter(descriptor->frameNumber_, sensorTimestamp);
>
>  	LOG(HAL, Debug) << "Request " << request->cookie() << " completed with "
> -			<< descriptor.buffers_.size() << " streams";
> +			<< descriptor->buffers_.size() << " streams";
>
>  	/*
>  	 * Generate the metadata associated with the captured buffers.
> @@ -1186,16 +1192,16 @@ void CameraDevice::requestComplete(Request *request)
>  	 * Notify if the metadata generation has failed, but continue processing
>  	 * buffers and return an empty metadata pack.
>  	 */
> -	std::unique_ptr<CameraMetadata> resultMetadata = getResultMetadata(descriptor);
> +	std::unique_ptr<CameraMetadata> resultMetadata = getResultMetadata(*descriptor);
>  	if (!resultMetadata) {
> -		notifyError(descriptor.frameNumber_, nullptr, CAMERA3_MSG_ERROR_RESULT);
> +		notifyError(descriptor->frameNumber_, nullptr, CAMERA3_MSG_ERROR_RESULT);
>
>  		/* The camera framework expects an empty metadata pack on error. */
>  		resultMetadata = std::make_unique<CameraMetadata>(0, 0);
>  	}
>
>  	/* Handle post-processing. */
> -	for (camera3_stream_buffer_t &buffer : descriptor.buffers_) {
> +	for (camera3_stream_buffer_t &buffer : descriptor->buffers_) {
>  		CameraStream *cameraStream =
>  			static_cast<CameraStream *>(buffer.stream->priv);
>
> @@ -1206,13 +1212,13 @@ void CameraDevice::requestComplete(Request *request)
>  		if (!src) {
>  			LOG(HAL, Error) << "Failed to find a source stream buffer";
>  			buffer.status = CAMERA3_BUFFER_STATUS_ERROR;
> -			notifyError(descriptor.frameNumber_, buffer.stream,
> +			notifyError(descriptor->frameNumber_, buffer.stream,
>  				    CAMERA3_MSG_ERROR_BUFFER);
>  			continue;
>  		}
>
>  		int ret = cameraStream->process(*src, buffer,
> -						descriptor.settings_,
> +						descriptor->settings_,
>  						resultMetadata.get());
>  		/*
>  		 * Return the FrameBuffer to the CameraStream now that we're
> @@ -1223,13 +1229,16 @@ void CameraDevice::requestComplete(Request *request)
>
>  		if (ret) {
>  			buffer.status = CAMERA3_BUFFER_STATUS_ERROR;
> -			notifyError(descriptor.frameNumber_, buffer.stream,
> +			notifyError(descriptor->frameNumber_, buffer.stream,
>  				    CAMERA3_MSG_ERROR_BUFFER);
>  		}
>  	}
>
>  	captureResult.result = resultMetadata->get();
>  	callbacks_->process_capture_result(callbacks_, &captureResult);
> +
> +	MutexLocker descriptorsLock(descriptorsMutex_);
> +	descriptors_.pop();
>  }
>
>  std::string CameraDevice::logPrefix() const
> diff --git a/src/android/camera_device.h b/src/android/camera_device.h
> index 43eb5895..9ec510d5 100644
> --- a/src/android/camera_device.h
> +++ b/src/android/camera_device.h
> @@ -10,6 +10,7 @@
>  #include <map>
>  #include <memory>
>  #include <mutex>
> +#include <queue>
>  #include <vector>
>
>  #include <hardware/camera3.h>
> @@ -125,7 +126,7 @@ private:
>  	std::vector<CameraStream> streams_;
>
>  	libcamera::Mutex descriptorsMutex_; /* Protects descriptors_. */
> -	std::map<uint64_t, Camera3RequestDescriptor> descriptors_;
> +	std::queue<std::unique_ptr<Camera3RequestDescriptor>> descriptors_;
>
>  	std::string maker_;
>  	std::string model_;
> --
> 2.31.0
>

Patch
diff mbox series 

diff --git a/src/android/camera_device.cpp b/src/android/camera_device.cpp
index 9287ea07..e815f7a0 100644
--- a/src/android/camera_device.cpp
+++ b/src/android/camera_device.cpp
@@ -457,7 +457,8 @@  void CameraDevice::stop()
 	worker_.stop();
 	camera_->stop();
 
-	descriptors_.clear();
+	descriptors_ = {};
+
 	state_ = State::Stopped;
 }
 
@@ -955,7 +956,8 @@  int CameraDevice::processCaptureRequest(camera3_capture_request_t *camera3Reques
 	 * The descriptor and the associated memory reserved here are freed
 	 * at request complete time.
 	 */
-	Camera3RequestDescriptor descriptor(camera_.get(), camera3Request);
+	auto descriptor = std::make_unique<Camera3RequestDescriptor>(camera_.get(),
+								     camera3Request);
 
 	/*
 	 * \todo The Android request model is incremental, settings passed in
@@ -966,12 +968,12 @@  int CameraDevice::processCaptureRequest(camera3_capture_request_t *camera3Reques
 	if (camera3Request->settings)
 		lastSettings_ = camera3Request->settings;
 	else
-		descriptor.settings_ = lastSettings_;
+		descriptor->settings_ = lastSettings_;
+
+	LOG(HAL, Debug) << "Queueing request " << descriptor->request_->cookie()
+			<< " with " << descriptor->buffers_.size() << " streams";
 
-	LOG(HAL, Debug) << "Queueing request " << descriptor.request_->cookie()
-			<< " with " << descriptor.buffers_.size() << " streams";
-	for (unsigned int i = 0; i < descriptor.buffers_.size(); ++i) {
-		const camera3_stream_buffer_t &camera3Buffer = descriptor.buffers_[i];
+	for (const auto &[i, camera3Buffer] : utils::enumerate(descriptor->buffers_)) {
 		camera3_stream *camera3Stream = camera3Buffer.stream;
 		CameraStream *cameraStream = static_cast<CameraStream *>(camera3Stream->priv);
 
@@ -1007,12 +1009,12 @@  int CameraDevice::processCaptureRequest(camera3_capture_request_t *camera3Reques
 			 * associate it with the Camera3RequestDescriptor for
 			 * lifetime management only.
 			 */
-			descriptor.frameBuffers_.push_back(
+			descriptor->frameBuffers_.push_back(
 				createFrameBuffer(*camera3Buffer.buffer,
 						  cameraStream->configuration().pixelFormat,
 						  cameraStream->configuration().size));
 
-			buffer = descriptor.frameBuffers_.back().get();
+			buffer = descriptor->frameBuffers_.back().get();
 			acquireFence = camera3Buffer.acquire_fence;
 			LOG(HAL, Debug) << ss.str() << " (direct)";
 			break;
@@ -1035,7 +1037,7 @@  int CameraDevice::processCaptureRequest(camera3_capture_request_t *camera3Reques
 			return -ENOMEM;
 		}
 
-		descriptor.request_->addBuffer(cameraStream->stream(), buffer,
+		descriptor->request_->addBuffer(cameraStream->stream(), buffer,
 					       acquireFence);
 	}
 
@@ -1043,7 +1045,7 @@  int CameraDevice::processCaptureRequest(camera3_capture_request_t *camera3Reques
 	 * Translate controls from Android to libcamera and queue the request
 	 * to the CameraWorker thread.
 	 */
-	int ret = processControls(&descriptor);
+	int ret = processControls(descriptor.get());
 	if (ret)
 		return ret;
 
@@ -1071,11 +1073,11 @@  int CameraDevice::processCaptureRequest(camera3_capture_request_t *camera3Reques
 		state_ = State::Running;
 	}
 
-	CaptureRequest *request = descriptor.request_.get();
+	CaptureRequest *request = descriptor->request_.get();
 
 	{
 		MutexLocker descriptorsLock(descriptorsMutex_);
-		descriptors_[descriptor.request_->cookie()] = std::move(descriptor);
+		descriptors_.push(std::move(descriptor));
 	}
 
 	worker_.queueRequest(request);
@@ -1085,26 +1087,28 @@  int CameraDevice::processCaptureRequest(camera3_capture_request_t *camera3Reques
 
 void CameraDevice::requestComplete(Request *request)
 {
-	decltype(descriptors_)::node_type node;
+	Camera3RequestDescriptor *descriptor;
 	{
 		MutexLocker descriptorsLock(descriptorsMutex_);
-		auto it = descriptors_.find(request->cookie());
-		if (it == descriptors_.end()) {
-			/*
-			 * \todo Clarify if the Camera has to be closed on
-			 * ERROR_DEVICE and possibly demote the Fatal to simple
-			 * Error.
-			 */
-			notifyError(0, nullptr, CAMERA3_MSG_ERROR_DEVICE);
-			LOG(HAL, Fatal)
-				<< "Unknown request: " << request->cookie();
+		ASSERT(!descriptors_.empty());
+		descriptor = descriptors_.front().get();
+	}
 
-			return;
-		}
+	if (descriptor->request_->cookie() != request->cookie()) {
+		/*
+		 * \todo Clarify if the Camera has to be closed on
+		 * ERROR_DEVICE and possibly demote the Fatal to simple
+		 * Error.
+		 */
+		notifyError(0, nullptr, CAMERA3_MSG_ERROR_DEVICE);
+		LOG(HAL, Fatal)
+			<< "Out-of-order completion for request "
+			<< utils::hex(request->cookie());
 
-		node = descriptors_.extract(it);
+		MutexLocker descriptorsLock(descriptorsMutex_);
+		descriptors_.pop();
+		return;
 	}
-	Camera3RequestDescriptor &descriptor = node.mapped();
 
 	/*
 	 * Prepare the capture result for the Android camera stack.
@@ -1113,9 +1117,9 @@  void CameraDevice::requestComplete(Request *request)
 	 * post-processing/compression fails.
 	 */
 	camera3_capture_result_t captureResult = {};
-	captureResult.frame_number = descriptor.frameNumber_;
-	captureResult.num_output_buffers = descriptor.buffers_.size();
-	for (camera3_stream_buffer_t &buffer : descriptor.buffers_) {
+	captureResult.frame_number = descriptor->frameNumber_;
+	captureResult.num_output_buffers = descriptor->buffers_.size();
+	for (camera3_stream_buffer_t &buffer : descriptor->buffers_) {
 		CameraStream *cameraStream =
 			static_cast<CameraStream *>(buffer.stream->priv);
 
@@ -1135,7 +1139,7 @@  void CameraDevice::requestComplete(Request *request)
 		buffer.release_fence = -1;
 		buffer.status = CAMERA3_BUFFER_STATUS_OK;
 	}
-	captureResult.output_buffers = descriptor.buffers_.data();
+	captureResult.output_buffers = descriptor->buffers_.data();
 	captureResult.partial_result = 1;
 
 	/*
@@ -1147,11 +1151,11 @@  void CameraDevice::requestComplete(Request *request)
 				<< " not successfully completed: "
 				<< request->status();
 
-		notifyError(descriptor.frameNumber_, nullptr,
+		notifyError(descriptor->frameNumber_, nullptr,
 			    CAMERA3_MSG_ERROR_REQUEST);
 
 		captureResult.partial_result = 0;
-		for (camera3_stream_buffer_t &buffer : descriptor.buffers_) {
+		for (camera3_stream_buffer_t &buffer : descriptor->buffers_) {
 			/*
 			 * Signal to the framework it has to handle fences that
 			 * have not been waited on by setting the release fence
@@ -1164,6 +1168,8 @@  void CameraDevice::requestComplete(Request *request)
 
 		callbacks_->process_capture_result(callbacks_, &captureResult);
 
+		MutexLocker descriptorsLock(descriptorsMutex_);
+		descriptors_.pop();
 		return;
 	}
 
@@ -1175,10 +1181,10 @@  void CameraDevice::requestComplete(Request *request)
 	 */
 	uint64_t sensorTimestamp = static_cast<uint64_t>(request->metadata()
 							 .get(controls::SensorTimestamp));
-	notifyShutter(descriptor.frameNumber_, sensorTimestamp);
+	notifyShutter(descriptor->frameNumber_, sensorTimestamp);
 
 	LOG(HAL, Debug) << "Request " << request->cookie() << " completed with "
-			<< descriptor.buffers_.size() << " streams";
+			<< descriptor->buffers_.size() << " streams";
 
 	/*
 	 * Generate the metadata associated with the captured buffers.
@@ -1186,16 +1192,16 @@  void CameraDevice::requestComplete(Request *request)
 	 * Notify if the metadata generation has failed, but continue processing
 	 * buffers and return an empty metadata pack.
 	 */
-	std::unique_ptr<CameraMetadata> resultMetadata = getResultMetadata(descriptor);
+	std::unique_ptr<CameraMetadata> resultMetadata = getResultMetadata(*descriptor);
 	if (!resultMetadata) {
-		notifyError(descriptor.frameNumber_, nullptr, CAMERA3_MSG_ERROR_RESULT);
+		notifyError(descriptor->frameNumber_, nullptr, CAMERA3_MSG_ERROR_RESULT);
 
 		/* The camera framework expects an empty metadata pack on error. */
 		resultMetadata = std::make_unique<CameraMetadata>(0, 0);
 	}
 
 	/* Handle post-processing. */
-	for (camera3_stream_buffer_t &buffer : descriptor.buffers_) {
+	for (camera3_stream_buffer_t &buffer : descriptor->buffers_) {
 		CameraStream *cameraStream =
 			static_cast<CameraStream *>(buffer.stream->priv);
 
@@ -1206,13 +1212,13 @@  void CameraDevice::requestComplete(Request *request)
 		if (!src) {
 			LOG(HAL, Error) << "Failed to find a source stream buffer";
 			buffer.status = CAMERA3_BUFFER_STATUS_ERROR;
-			notifyError(descriptor.frameNumber_, buffer.stream,
+			notifyError(descriptor->frameNumber_, buffer.stream,
 				    CAMERA3_MSG_ERROR_BUFFER);
 			continue;
 		}
 
 		int ret = cameraStream->process(*src, buffer,
-						descriptor.settings_,
+						descriptor->settings_,
 						resultMetadata.get());
 		/*
 		 * Return the FrameBuffer to the CameraStream now that we're
@@ -1223,13 +1229,16 @@  void CameraDevice::requestComplete(Request *request)
 
 		if (ret) {
 			buffer.status = CAMERA3_BUFFER_STATUS_ERROR;
-			notifyError(descriptor.frameNumber_, buffer.stream,
+			notifyError(descriptor->frameNumber_, buffer.stream,
 				    CAMERA3_MSG_ERROR_BUFFER);
 		}
 	}
 
 	captureResult.result = resultMetadata->get();
 	callbacks_->process_capture_result(callbacks_, &captureResult);
+
+	MutexLocker descriptorsLock(descriptorsMutex_);
+	descriptors_.pop();
 }
 
 std::string CameraDevice::logPrefix() const
diff --git a/src/android/camera_device.h b/src/android/camera_device.h
index 43eb5895..9ec510d5 100644
--- a/src/android/camera_device.h
+++ b/src/android/camera_device.h
@@ -10,6 +10,7 @@ 
 #include <map>
 #include <memory>
 #include <mutex>
+#include <queue>
 #include <vector>
 
 #include <hardware/camera3.h>
@@ -125,7 +126,7 @@  private:
 	std::vector<CameraStream> streams_;
 
 	libcamera::Mutex descriptorsMutex_; /* Protects descriptors_. */
-	std::map<uint64_t, Camera3RequestDescriptor> descriptors_;
+	std::queue<std::unique_ptr<Camera3RequestDescriptor>> descriptors_;
 
 	std::string maker_;
 	std::string model_;