StimBuff: Use a single StagingBuffer for all StimFrames

We now allocate all the stimFrames for a StimBuffer using a
single StagingBuffer. This gives us all the benefits we're
looking for (pinning, alignment, etc).

include/user/stimulusBuffer.h

@@ -6,6 +6,7 @@
 #include <memory>
 #include <user/spMcRingBuffer.h>
 #include <user/stagingBuffer.h>
+#include <user/frameAssemblyDesc.h>
 #include "stimulusFrame.h"
 #include "deviceAttachmentSpec.h"
 
@@ -30,15 +31,15 @@ public:
 			&deviceAttachmentSpec,
 		int histbuffMs,
 		const StagingBuffer::IOEngineConstraints& inputEngineConstraints,
-		const StagingBuffer::IOEngineConstraints& outputEngineConstraints,
-		size_t nSlotsPerStimFrame)
+		const StagingBuffer::IOEngineConstraints& outputEngineConstraints)
 	: parent(parent),
 	deviceAttachmentSpec(deviceAttachmentSpec),
 	histbuffMs(histbuffMs),
-	ringBuffer(
-		static_cast<size_t>(histbuffMs / CONFIG_STIMBUFF_FRAME_PERIOD_MS),
-		inputEngineConstraints, outputEngineConstraints,
-		nSlotsPerStimFrame)
+	stagingBuffer(
+		inputEngineConstraints,
+		outputEngineConstraints,
+		static_cast<size_t>(histbuffMs / CONFIG_STIMBUFF_FRAME_PERIOD_MS)),
+	ringBuffer(static_cast<std::shared_ptr<FrameAssemblyDesc>>(stagingBuffer))
 	{}
 
 	virtual ~StimulusBuffer() = default;
@@ -53,6 +54,7 @@ public:
 	StimulusProducer& parent;
 	std::shared_ptr<device::DeviceAttachmentSpec> deviceAttachmentSpec;
 	int histbuffMs;
+	StagingBuffer stagingBuffer;
 	SpMcRingBuffer ringBuffer;
 };