libcamera: framebuffer: Prevent modifying the number of metadata planes

The number of metadata planes should always match the number of frame
buffer planes. Enforce this by making the vector private and providing
accessor functions.

As this changes the public API, update all in-tree users accordingly.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
Reviewed-by: Jean-Michel Hautbois <jeanmichel.hautbois@ideasonboard.com>
Reviewed-by: Hirokazu Honda <hiroh@chromium.org>

Documentation/guides/application-developer.rst

@@ -427,10 +427,10 @@ the Frame sequence number and details of the planes.
    std::cout << " seq: " << std::setw(6) << std::setfill('0') << metadata.sequence << " bytesused: ";
 
    unsigned int nplane = 0;
-   for (const FrameMetadata::Plane &plane : metadata.planes)
+   for (const FrameMetadata::Plane &plane : metadata.planes())
    {
        std::cout << plane.bytesused;
-       if (++nplane < metadata.planes.size()) std::cout << "/";
+       if (++nplane < metadata.planes().size()) std::cout << "/";
    }
 
    std::cout << std::endl;

include/libcamera/framebuffer.h

@@ -13,6 +13,7 @@
 #include <vector>
 
 #include <libcamera/base/class.h>
+#include <libcamera/base/span.h>
 
 #include <libcamera/file_descriptor.h>
 
@@ -34,7 +35,14 @@ struct FrameMetadata {
 	Status status;
 	unsigned int sequence;
 	uint64_t timestamp;
-	std::vector<Plane> planes;
+
+	Span<Plane> planes() { return planes_; }
+	Span<const Plane> planes() const { return planes_; }
+
+private:
+	friend class FrameBuffer;
+
+	std::vector<Plane> planes_;
 };
 
 class FrameBuffer final : public Extensible

src/cam/camera_session.cpp

@@ -374,9 +374,9 @@ void CameraSession::processRequest(Request *request)
 		     << " bytesused: ";
 
 		unsigned int nplane = 0;
-		for (const FrameMetadata::Plane &plane : metadata.planes) {
+		for (const FrameMetadata::Plane &plane : metadata.planes()) {
 			info << plane.bytesused;
-			if (++nplane < metadata.planes.size())
+			if (++nplane < metadata.planes().size())
 				info << "/";
 		}
 	}

src/cam/file_sink.cpp

@@ -110,7 +110,7 @@ void FileSink::writeBuffer(const Stream *stream, FrameBuffer *buffer)
 
 	for (unsigned int i = 0; i < buffer->planes().size(); ++i) {
 		const FrameBuffer::Plane &plane = buffer->planes()[i];
-		const FrameMetadata::Plane &meta = buffer->metadata().planes[i];
+		const FrameMetadata::Plane &meta = buffer->metadata().planes()[i];
 
 		uint8_t *data = planeData_[&plane];
 		unsigned int length = std::min(meta.bytesused, plane.length);

src/libcamera/framebuffer.cpp

@@ -91,8 +91,14 @@ LOG_DEFINE_CATEGORY(Buffer)
  */
 
 /**
- * \var FrameMetadata::planes
- * \brief Array of per-plane metadata
+ * \fn FrameMetadata::planes()
+ * \copydoc FrameMetadata::planes() const
+ */
+
+/**
+ * \fn FrameMetadata::planes() const
+ * \brief Retrieve the array of per-plane metadata
+ * \return The array of per-plane metadata
  */
 
 /**
@@ -210,7 +216,7 @@ FrameBuffer::FrameBuffer(const std::vector<Plane> &planes, unsigned int cookie)
 	: Extensible(std::make_unique<Private>()), planes_(planes),
 	  cookie_(cookie)
 {
-	metadata_.planes.resize(planes_.size());
+	metadata_.planes_.resize(planes_.size());
 
 	unsigned int offset = 0;
 	bool isContiguous = true;

src/libcamera/v4l2_videodevice.cpp

@@ -1543,7 +1543,7 @@ int V4L2VideoDevice::queueBuffer(FrameBuffer *buffer)
 			unsigned int length = 0;
 
 			for (auto [i, plane] : utils::enumerate(planes)) {
-				bytesused += metadata.planes[i].bytesused;
+				bytesused += metadata.planes()[i].bytesused;
 				length += plane.length;
 
 				if (i != planes.size() - 1 && bytesused != length) {
@@ -1567,7 +1567,7 @@ int V4L2VideoDevice::queueBuffer(FrameBuffer *buffer)
 			 * V4L2 buffer is guaranteed to be equal at this point.
 			 */
 			for (auto [i, plane] : utils::enumerate(planes)) {
-				v4l2Planes[i].bytesused = metadata.planes[i].bytesused;
+				v4l2Planes[i].bytesused = metadata.planes()[i].bytesused;
 				v4l2Planes[i].length = plane.length;
 			}
 		} else {
@@ -1575,7 +1575,7 @@ int V4L2VideoDevice::queueBuffer(FrameBuffer *buffer)
 			 * Single-planar API with a single plane in the buffer
 			 * is trivial to handle.
 			 */
-			buf.bytesused = metadata.planes[0].bytesused;
+			buf.bytesused = metadata.planes()[0].bytesused;
 			buf.length = planes[0].length;
 		}
 
@@ -1704,9 +1704,9 @@ FrameBuffer *V4L2VideoDevice::dequeueBuffer()
 				return buffer;
 			}
 
-			metadata.planes[i].bytesused =
+			metadata.planes()[i].bytesused =
 				std::min(plane.length, bytesused);
-			bytesused -= metadata.planes[i].bytesused;
+			bytesused -= metadata.planes()[i].bytesused;
 		}
 	} else if (multiPlanar) {
 		/*
@@ -1715,9 +1715,9 @@ FrameBuffer *V4L2VideoDevice::dequeueBuffer()
 		 * V4L2 buffer is guaranteed to be equal at this point.
 		 */
 		for (unsigned int i = 0; i < numV4l2Planes; ++i)
-			metadata.planes[i].bytesused = planes[i].bytesused;
+			metadata.planes()[i].bytesused = planes[i].bytesused;
 	} else {
-		metadata.planes[0].bytesused = buf.bytesused;
+		metadata.planes()[0].bytesused = buf.bytesused;
 	}
 
 	return buffer;

src/qcam/main_window.cpp

@@ -756,7 +756,7 @@ void MainWindow::processViewfinder(FrameBuffer *buffer)
 
 	qDebug().noquote()
 		<< QString("seq: %1").arg(metadata.sequence, 6, 10, QLatin1Char('0'))
-		<< "bytesused:" << metadata.planes[0].bytesused
+		<< "bytesused:" << metadata.planes()[0].bytesused
 		<< "timestamp:" << metadata.timestamp
 		<< "fps:" << Qt::fixed << qSetRealNumberPrecision(2) << fps;
 

src/qcam/viewfinder_gl.cpp

@@ -125,7 +125,7 @@ void ViewFinderGL::render(libcamera::FrameBuffer *buffer,
 	/*
 	 * \todo Get the stride from the buffer instead of computing it naively
 	 */
-	stride_ = buffer->metadata().planes[0].bytesused / size_.height();
+	stride_ = buffer->metadata().planes()[0].bytesused / size_.height();
 	update();
 	buffer_ = buffer;
 }

src/qcam/viewfinder_qt.cpp

@@ -87,7 +87,7 @@ void ViewFinderQt::render(libcamera::FrameBuffer *buffer,
 	}
 
 	unsigned char *memory = mem.data();
-	size_t size = buffer->metadata().planes[0].bytesused;
+	size_t size = buffer->metadata().planes()[0].bytesused;
 
 	{
 		QMutexLocker locker(&mutex_);

src/v4l2/v4l2_camera_proxy.cpp

@@ -211,7 +211,7 @@ void V4L2CameraProxy::updateBuffers()
 
 		switch (fmd.status) {
 		case FrameMetadata::FrameSuccess:
-			buf.bytesused = fmd.planes[0].bytesused;
+			buf.bytesused = fmd.planes()[0].bytesused;
 			buf.field = V4L2_FIELD_NONE;
 			buf.timestamp.tv_sec = fmd.timestamp / 1000000000;
 			buf.timestamp.tv_usec = fmd.timestamp % 1000000;