1 files changed, 108 insertions, 0 deletions
diff --git a/src/ipa/libipa/fc_queue.h b/src/ipa/libipa/fc_queue.h
new file mode 100644
index 00000000..4f5cb5d3
--- /dev/null
+++ b/src/ipa/libipa/fc_queue.h
@@ -0,0 +1,108 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+/*
+ * Copyright (C) 2022, Google Inc.
+ *
+ * fc_queue.h - IPA Frame context queue
+ */
+
+#pragma once
+
+#include <vector>
+
+#include <libcamera/base/log.h>
+
+namespace libcamera {
+
+LOG_DECLARE_CATEGORY(FCQueue)
+
+namespace ipa {
+
+template<typename FrameContext>
+class FCQueue
+{
+public:
+	FCQueue(unsigned int size)
+		: contexts_(size)
+	{
+	}
+
+	void clear()
+	{
+		for (FrameContext &ctx : contexts_)
+			ctx.frame = 0;
+	}
+
+	FrameContext &alloc(const uint32_t frame)
+	{
+		FrameContext &frameContext = contexts_[frame % contexts_.size()];
+
+		/*
+		 * Do not re-initialise if a get() call has already fetched this
+		 * frame context to preseve the context.
+		 *
+		 * \todo If the the sequence number of the context to initialise
+		 * is smaller than the sequence number of the queue slot to use,
+		 * it means that we had a serious request underrun and more
+		 * frames than the queue size has been produced since the last
+		 * time the application has queued a request. Does this deserve
+		 * an error condition ?
+		 */
+		if (frame != 0 && frame <= frameContext.frame)
+			LOG(FCQueue, Warning)
+				<< "Frame " << frame << " already initialised";
+		else
+			init(frameContext, frame);
+
+		return frameContext;
+	}
+
+	FrameContext &get(uint32_t frame)
+	{
+		FrameContext &frameContext = contexts_[frame % contexts_.size()];
+
+		/*
+		 * If the IPA algorithms try to access a frame context slot which
+		 * has been already overwritten by a newer context, it means the
+		 * frame context queue has overflowed and the desired context
+		 * has been forever lost. The pipeline handler shall avoid
+		 * queueing more requests to the IPA than the frame context
+		 * queue size.
+		 */
+		if (frame < frameContext.frame)
+			LOG(FCQueue, Fatal) << "Frame context for " << frame
+					    << " has been overwritten by "
+					    << frameContext.frame;
+
+		if (frame == frameContext.frame)
+			return frameContext;
+
+		/*
+		 * The frame context has been retrieved before it was
+		 * initialised through the initialise() call. This indicates an
+		 * algorithm attempted to access a Frame context before it was
+		 * queued to the IPA. Controls applied for this request may be
+		 * left unhandled.
+		 *
+		 * \todo Set an error flag for per-frame control errors.
+		 */
+		LOG(FCQueue, Warning)
+			<< "Obtained an uninitialised FrameContext for " << frame;
+
+		init(frameContext, frame);
+
+		return frameContext;
+	}
+
+private:
+	void init(FrameContext &frameContext, const uint32_t frame)
+	{
+		frameContext = {};
+		frameContext.frame = frame;
+	}
+
+	std::vector<FrameContext> contexts_;
+};
+
+} /* namespace ipa */
+
+} /* namespace libcamera */