[libcamera-devel] [PATCH v3 31/33] qcam: Cache buffer memory mapping

[Niklas Söderlund]

With the buffer allocator in use it's possible to cache the dmabuf
memory mappings when starting the camera instead of mapping and
unmapping them each time.

Signed-off-by: Niklas Söderlund <niklas.soderlund at ragnatech.se>
Reviewed-by: Laurent Pinchart <laurent.pinchart at ideasonboard.com>
---
 src/qcam/main_window.cpp | 28 ++++++++++++++++++++++------
 src/qcam/main_window.h   |  1 +
 2 files changed, 23 insertions(+), 6 deletions(-)

diff --git a/src/qcam/main_window.cpp b/src/qcam/main_window.cpp
index 701a2b9a73d53d96..047bf15ea7c188f7 100644
--- a/src/qcam/main_window.cpp
+++ b/src/qcam/main_window.cpp
@@ -201,6 +201,13 @@ int MainWindow::startCapture()
 		}
 
 		requests.push_back(request);
+
+		/* Map memory buffers and cache the mappings. */
+		const FrameBuffer::Plane &plane = buffer->planes().front();
+		void *memory = mmap(NULL, plane.length, PROT_READ, MAP_SHARED,
+				    plane.fd.fd(), 0);
+		mappedBuffers_[plane.fd.fd()] =
+			std::make_pair(memory, plane.length);
 	}
 
 	titleTimer_.start(2000);
@@ -230,6 +237,13 @@ error:
 	for (Request *request : requests)
 		delete request;
 
+	for (auto &iter : mappedBuffers_) {
+		void *memory = iter.second.first;
+		unsigned int length = iter.second.second;
+		munmap(memory, length);
+	}
+	mappedBuffers_.clear();
+
 	camera_->freeBuffers();
 	return ret;
 }
@@ -243,6 +257,13 @@ void MainWindow::stopCapture()
 	if (ret)
 		std::cout << "Failed to stop capture" << std::endl;
 
+	for (auto &iter : mappedBuffers_) {
+		void *memory = iter.second.first;
+		unsigned int length = iter.second.second;
+		munmap(memory, length);
+	}
+	mappedBuffers_.clear();
+
 	camera_->freeBuffers();
 	isCapturing_ = false;
 
@@ -297,15 +318,10 @@ int MainWindow::display(FrameBuffer *buffer)
 	if (buffer->planes().size() != 1)
 		return -EINVAL;
 
-	/* \todo Once the FrameBuffer is done cache mapped memory. */
 	const FrameBuffer::Plane &plane = buffer->planes().front();
-	void *memory = mmap(NULL, plane.length, PROT_READ, MAP_SHARED,
-			    plane.fd.fd(), 0);
-
+	void *memory = mappedBuffers_[plane.fd.fd()].first;
 	unsigned char *raw = static_cast<unsigned char *>(memory);
 	viewfinder_->display(raw, buffer->metadata().planes[0].bytesused);
 
-	munmap(memory, plane.length);
-
 	return 0;
 }
diff --git a/src/qcam/main_window.h b/src/qcam/main_window.h
index 05cde4ceab5f7ea1..04fb9e3ea869c3fb 100644
--- a/src/qcam/main_window.h
+++ b/src/qcam/main_window.h
@@ -71,6 +71,7 @@ private:
 	uint32_t framesCaptured_;
 
 	ViewFinder *viewfinder_;
+	std::map<int, std::pair<void *, unsigned int>> mappedBuffers_;
 };
 
 #endif /* __QCAM_MAIN_WINDOW__ */
-- 
2.24.1