libcamera: pipeline: ipu3: Cancel unused buffers

When the CIO2 returns a cancelled buffer, we will not queue buffers
to the IMGU.

These buffers should be explicitly marked as cancelled to ensure
the application knows there is no valid metadata or frame data
provided in the buffer.

Provide a cancel() method on the FrameBuffer to allow explicitly
cancelling a buffer.

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

include/libcamera/buffer.h

@@ -53,6 +53,8 @@ public:
 	unsigned int cookie() const { return cookie_; }
 	void setCookie(unsigned int cookie) { cookie_ = cookie; }
 
+	void cancel() { metadata_.status = FrameMetadata::FrameCancelled; }
+
 private:
 	LIBCAMERA_DISABLE_COPY_AND_MOVE(FrameBuffer)
 

src/libcamera/buffer.cpp

@@ -226,6 +226,14 @@ FrameBuffer::FrameBuffer(const std::vector<Plane> &planes, unsigned int cookie)
  * core never modifies the buffer cookie.
  */
 
+/**
+ * \fn FrameBuffer::cancel()
+ * \brief Marks the buffer as cancelled
+ *
+ * If a buffer is not used by a request, it shall be marked as cancelled to
+ * indicate that the metadata is invalid.
+ */
+
 /**
  * \class MappedBuffer
  * \brief Provide an interface to support managing memory mapped buffers

src/libcamera/pipeline/ipu3/ipu3.cpp

@@ -1257,8 +1257,11 @@ void IPU3CameraData::cio2BufferReady(FrameBuffer *buffer)
 
 	/* If the buffer is cancelled force a complete of the whole request. */
 	if (buffer->metadata().status == FrameMetadata::FrameCancelled) {
-		for (auto it : request->buffers())
-			pipe_->completeBuffer(request, it.second);
+		for (auto it : request->buffers()) {
+			FrameBuffer *b = it.second;
+			b->cancel();
+			pipe_->completeBuffer(request, b);
+		}
 
 		frameInfos_.remove(info);
 		pipe_->completeRequest(request);