libcamera: buffer: Add an accessor to the BufferMemory

Buffer instances reference memory, which is modelled internally by a
BufferMemory instance. Store a pointer to the BufferMemory in the Buffer
class, and populate it when the buffer is queued to the camera through a
request. This is useful for applications to access the buffer memory in
the buffer or request completion handler.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Niklas Söderlund <niklas.soderlund@ragnatech.se>

7 files changed, 23 insertions, 11 deletions

diff --git a/src/cam/buffer_writer.cpp b/src/cam/buffer_writer.cpp
index b7f2ed4f..1c044b06 100644
--- a/src/cam/buffer_writer.cpp
+++ b/src/cam/buffer_writer.cpp
@@ -19,8 +19,7 @@ BufferWriter::BufferWriter(const std::string &pattern)
 {
 }
 
-int BufferWriter::write(libcamera::Buffer *buffer, libcamera::BufferMemory *mem,
-			const std::string &streamName)
+int BufferWriter::write(libcamera::Buffer *buffer, const std::string &streamName)
 {
 	std::string filename;
 	size_t pos;
@@ -41,6 +40,7 @@ int BufferWriter::write(libcamera::Buffer *buffer, libcamera::BufferMemory *mem,
 	if (fd == -1)
 		return -errno;
 
+	libcamera::BufferMemory *mem = buffer->mem();
 	for (libcamera::Plane &plane : mem->planes()) {
 		void *data = plane.mem();
 		unsigned int length = plane.length();
diff --git a/src/cam/buffer_writer.h b/src/cam/buffer_writer.h
index 9bea205f..7bf785d1 100644
--- a/src/cam/buffer_writer.h
+++ b/src/cam/buffer_writer.h
@@ -16,8 +16,7 @@ class BufferWriter
 public:
 	BufferWriter(const std::string &pattern = "frame-#.bin");
 
-	int write(libcamera::Buffer *buffer, libcamera::BufferMemory *mem,
-		  const std::string &streamName);
+	int write(libcamera::Buffer *buffer, const std::string &streamName);
 
 private:
 	std::string pattern_;
diff --git a/src/cam/capture.cpp b/src/cam/capture.cpp
index 5ffa4ae2..df9602de 100644
--- a/src/cam/capture.cpp
+++ b/src/cam/capture.cpp
@@ -154,7 +154,6 @@ void Capture::requestComplete(Request *request, const std::map<Stream *, Buffer
 	for (auto it = buffers.begin(); it != buffers.end(); ++it) {
 		Stream *stream = it->first;
 		Buffer *buffer = it->second;
-		BufferMemory *mem = &stream->buffers()[buffer->index()];
 		const std::string &name = streamName_[stream];
 
 		info << " " << name
@@ -163,7 +162,7 @@ void Capture::requestComplete(Request *request, const std::map<Stream *, Buffer
 		     << " bytesused: " << buffer->bytesused();
 
 		if (writer_)
-			writer_->write(buffer, mem, name);
+			writer_->write(buffer, name);
 	}
 
 	std::cout << info.str() << std::endl;
diff --git a/src/libcamera/buffer.cpp b/src/libcamera/buffer.cpp
index 99358633..fe29c2f6 100644
--- a/src/libcamera/buffer.cpp
+++ b/src/libcamera/buffer.cpp
@@ -301,6 +301,17 @@ Buffer::Buffer(unsigned int index, const Buffer *metadata)
  */
 
 /**
+ * \fn Buffer::mem()
+ * \brief Retrieve the BufferMemory this buffer is associated with
+ *
+ * The association between the buffer and a BufferMemory instance is valid from
+ * the time the request containing this buffer is queued to a camera to the end
+ * of that request's completion handler.
+ *
+ * \return The BufferMemory this buffer is associated with
+ */
+
+/**
  * \fn Buffer::bytesused()
  * \brief Retrieve the number of bytes occupied by the data in the buffer
  * \return Number of bytes occupied in the buffer
diff --git a/src/libcamera/camera.cpp b/src/libcamera/camera.cpp
index af69607b..db15fd46 100644
--- a/src/libcamera/camera.cpp
+++ b/src/libcamera/camera.cpp
@@ -811,10 +811,14 @@ int Camera::queueRequest(Request *request)
 
 	for (auto const &it : request->buffers()) {
 		Stream *stream = it.first;
+		Buffer *buffer = it.second;
+
 		if (activeStreams_.find(stream) == activeStreams_.end()) {
 			LOG(Camera, Error) << "Invalid request";
 			return -EINVAL;
 		}
+
+		buffer->mem_ = &stream->buffers()[buffer->index_];
 	}
 
 	int ret = request->prepare();
diff --git a/src/qcam/main_window.cpp b/src/qcam/main_window.cpp
index 92f88832..5c26ab8e 100644
--- a/src/qcam/main_window.cpp
+++ b/src/qcam/main_window.cpp
@@ -221,7 +221,6 @@ void MainWindow::requestComplete(Request *request,
 
 	framesCaptured_++;
 
-	Stream *stream = buffers.begin()->first;
 	Buffer *buffer = buffers.begin()->second;
 
 	double fps = buffer->timestamp() - lastBufferTime_;
@@ -235,8 +234,7 @@ void MainWindow::requestComplete(Request *request,
 		  << " fps: " << std::fixed << std::setprecision(2) << fps
 		  << std::endl;
 
-	BufferMemory *mem = &stream->buffers()[buffer->index()];
-	display(buffer, mem);
+	display(buffer);
 
 	request = camera_->createRequest();
 	if (!request) {
@@ -261,8 +259,9 @@ void MainWindow::requestComplete(Request *request,
 	camera_->queueRequest(request);
 }
 
-int MainWindow::display(Buffer *buffer, BufferMemory *mem)
+int MainWindow::display(Buffer *buffer)
 {
+	BufferMemory *mem = buffer->mem();
 	if (mem->planes().size() != 1)
 		return -EINVAL;
 
diff --git a/src/qcam/main_window.h b/src/qcam/main_window.h
index b4f6f747..f58cb6a6 100644
--- a/src/qcam/main_window.h
+++ b/src/qcam/main_window.h
@@ -48,7 +48,7 @@ private:
 
 	void requestComplete(Request *request,
 			     const std::map<Stream *, Buffer *> &buffers);
-	int display(Buffer *buffer, BufferMemory *mem);
+	int display(Buffer *buffer);
 
 	QString title_;
 	QTimer titleTimer_;