pipeline: rpi: Simplify buffer id generation

Replace the buffer id generation in RPi::Stream with a simple integer
counter since ids don't get recycled any more.

Signed-off-by: Naushir Patuck <naush@raspberrypi.com>
Reviewed-by: Jacopo Mondi <jacopo.mondi@ideasonboard.com>
Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>

src/libcamera/pipeline/rpi/common/rpi_stream.cpp

@@ -56,7 +56,7 @@ void Stream::resetBuffers()
 void Stream::setExportedBuffers(std::vector<std::unique_ptr<FrameBuffer>> *buffers)
 {
 	for (auto const &buffer : *buffers)
-		bufferMap_.emplace(id_.get(), buffer.get());
+		bufferMap_.emplace(++id_, buffer.get());
 }
 
 const BufferMap &Stream::getBuffers() const
@@ -81,7 +81,7 @@ unsigned int Stream::getBufferId(FrameBuffer *buffer) const
 
 void Stream::setExportedBuffer(FrameBuffer *buffer)
 {
-	bufferMap_.emplace(id_.get(), buffer);
+	bufferMap_.emplace(++id_, buffer);
 }
 
 int Stream::prepareBuffers(unsigned int count)
@@ -152,9 +152,6 @@ void Stream::returnBuffer(FrameBuffer *buffer)
 	/* Push this buffer back into the queue to be used again. */
 	availableBuffers_.push(buffer);
 
-	/* Allow the buffer id to be reused. */
-	id_.release(getBufferId(buffer));
-
 	/*
 	 * Do we have any Request buffers that are waiting to be queued?
 	 * If so, do it now as availableBuffers_ will not be empty.
@@ -213,7 +210,7 @@ void Stream::clearBuffers()
 	requestBuffers_ = std::queue<FrameBuffer *>{};
 	internalBuffers_.clear();
 	bufferMap_.clear();
-	id_.reset();
+	id_ = 0;
 }
 
 int Stream::queueToDevice(FrameBuffer *buffer)

src/libcamera/pipeline/rpi/common/rpi_stream.h

@@ -54,13 +54,13 @@ public:
 	using StreamFlags = Flags<StreamFlag>;
 
 	Stream()
-		: flags_(StreamFlag::None), id_(BufferMask::MaskID)
+		: flags_(StreamFlag::None), id_(0)
 	{
 	}
 
 	Stream(const char *name, MediaEntity *dev, StreamFlags flags = StreamFlag::None)
 		: flags_(flags), name_(name),
-		  dev_(std::make_unique<V4L2VideoDevice>(dev)), id_(BufferMask::MaskID)
+		  dev_(std::make_unique<V4L2VideoDevice>(dev)), id_(0)
 	{
 	}
 
@@ -86,44 +86,6 @@ public:
 	void releaseBuffers();
 
 private:
-	class IdGenerator
-	{
-	public:
-		IdGenerator(unsigned int max)
-			: max_(max), id_(0)
-		{
-		}
-
-		unsigned int get()
-		{
-			unsigned int id;
-			if (!recycle_.empty()) {
-				id = recycle_.front();
-				recycle_.pop();
-			} else {
-				id = ++id_;
-				ASSERT(id_ <= max_);
-			}
-			return id;
-		}
-
-		void release(unsigned int id)
-		{
-			recycle_.push(id);
-		}
-
-		void reset()
-		{
-			id_ = 0;
-			recycle_ = {};
-		}
-
-	private:
-		unsigned int max_;
-		unsigned int id_;
-		std::queue<unsigned int> recycle_;
-	};
-
 	void clearBuffers();
 	int queueToDevice(FrameBuffer *buffer);
 
@@ -136,7 +98,7 @@ private:
 	std::unique_ptr<V4L2VideoDevice> dev_;
 
 	/* Tracks a unique id key for the bufferMap_ */
-	IdGenerator id_;
+	unsigned int id_;
 
 	/* All frame buffers associated with this device stream. */
 	BufferMap bufferMap_;