[libcamera-devel] [PATCH v3 6/8] android: camera_device: Add methods to get and return buffers

[Jacopo Mondi]

Add two methods to the CameraDevice class to retrieve and return
frame buffers associated to a stream from the memory pool reserved
in libcamera.

Protect accessing the vector of FrameBufer pointers with a
per-pool mutex in the get and return buffer methods.

Reviewed-by: Niklas Söderlund <niklas.soderlund at ragnatech.se>
Signed-off-by: Jacopo Mondi <jacopo at jmondi.org>
---
 src/android/camera_device.cpp | 34 +++++++++++++++++++++++++++++++++-
 src/android/camera_device.h   | 11 +++++++++--
 2 files changed, 42 insertions(+), 3 deletions(-)

diff --git a/src/android/camera_device.cpp b/src/android/camera_device.cpp
index f96ea7321a67..6ed56ff57dab 100644
--- a/src/android/camera_device.cpp
+++ b/src/android/camera_device.cpp
@@ -8,6 +8,7 @@
 #include "camera_device.h"
 #include "camera_ops.h"
 
+#include <mutex>
 #include <sys/mman.h>
 #include <tuple>
 #include <vector>
@@ -1400,11 +1401,42 @@ int CameraDevice::allocateBuffersPool(Stream *stream)
 	 * the HAL.
 	 */
 	for (const auto &frameBuffer : allocator_.buffers(stream))
-		bufferPool_[stream].push_back(frameBuffer.get());
+		bufferPool_[stream].buffers.push_back(frameBuffer.get());
 
 	return 0;
 }
 
+libcamera::FrameBuffer *CameraDevice::getBuffer(libcamera::Stream *stream)
+{
+	if (bufferPool_.find(stream) == bufferPool_.end())
+		return nullptr;
+
+	BufferPool *pool = &bufferPool_[stream];
+	std::lock_guard<std::mutex> locker(pool->mutex);
+
+	if (pool->buffers.empty()) {
+		LOG(HAL, Error) << "Buffer underrun";
+		return nullptr;
+	}
+
+	FrameBuffer *buffer = pool->buffers.front();
+	pool->buffers.erase(pool->buffers.begin());
+
+	return buffer;
+}
+
+void CameraDevice::returnBuffer(libcamera::Stream *stream,
+				libcamera::FrameBuffer *buffer)
+{
+	if (bufferPool_.find(stream) == bufferPool_.end())
+		return;
+
+	BufferPool *pool = &bufferPool_[stream];
+	std::lock_guard<std::mutex> locker(pool->mutex);
+
+	pool->buffers.push_back(buffer);
+}
+
 int CameraDevice::processCaptureRequest(camera3_capture_request_t *camera3Request)
 {
 	if (!camera3Request->num_output_buffers) {
diff --git a/src/android/camera_device.h b/src/android/camera_device.h
index 4cef34c01a49..5addffdc070a 100644
--- a/src/android/camera_device.h
+++ b/src/android/camera_device.h
@@ -9,6 +9,7 @@
 
 #include <map>
 #include <memory>
+#include <mutex>
 #include <tuple>
 #include <vector>
 
@@ -166,8 +167,11 @@ protected:
 	std::string logPrefix() const override;
 
 private:
-	using FrameBufferPool = std::map<libcamera::Stream *,
-					 std::vector<libcamera::FrameBuffer *>>;
+	struct BufferPool {
+		std::mutex mutex;
+		std::vector<libcamera::FrameBuffer *> buffers;
+	};
+	using FrameBufferPool = std::map<libcamera::Stream *, BufferPool>;
 
 	CameraDevice(unsigned int id, const std::shared_ptr<libcamera::Camera> &camera);
 
@@ -198,6 +202,9 @@ private:
 	std::tuple<uint32_t, uint32_t> calculateStaticMetadataSize();
 	libcamera::FrameBuffer *createFrameBuffer(const buffer_handle_t camera3buffer);
 	int allocateBuffersPool(libcamera::Stream *stream);
+	libcamera::FrameBuffer *getBuffer(libcamera::Stream *stream);
+	void returnBuffer(libcamera::Stream *stream,
+			  libcamera::FrameBuffer *buffer);
 
 	void notifyShutter(uint32_t frameNumber, uint64_t timestamp);
 	void notifyError(uint32_t frameNumber, camera3_stream_t *stream);
-- 
2.28.0