pipeline: rpi: Add RequiresMmap flag to RPi::Stream

Add a new RequiresMmap flag to the RPi::Stream class indicating that
buffers handled by the stream must be mmapped after allocation and
cached internally.

Add a new member function getBuffer(id) which can be used to obtain the
mapped buffers for a given buffer id.

Add a new member function acquireBuffer() which can be used to obtain
any mapped buffer that has not already been acquired by the caller.

As a drive-by, add the <algorithm> header to rpi_stream.cpp as it is
needed for the std::find_if() function.

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

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

@@ -888,7 +888,7 @@ void PipelineHandlerBase::mapBuffers(Camera *camera, const BufferMap &buffers, u
 	 */
 	for (auto const &it : buffers) {
 		bufferIds.push_back(IPABuffer(mask | it.first,
-					      it.second->planes()));
+					      it.second.buffer->planes()));
 		data->bufferIds_.insert(mask | it.first);
 	}
 

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

@@ -6,6 +6,10 @@
  */
 #include "rpi_stream.h"
 
+#include <algorithm>
+#include <tuple>
+#include <utility>
+
 #include <libcamera/base/log.h>
 
 /* Maximum number of buffer slots to allocate in the V4L2 device driver. */
@@ -17,8 +21,13 @@ LOG_DEFINE_CATEGORY(RPISTREAM)
 
 namespace RPi {
 
+const BufferObject Stream::errorBufferObject{ nullptr, false };
+
 void Stream::setFlags(StreamFlags flags)
 {
+	/* We don't want dynamic mmapping. */
+	ASSERT(!(flags & StreamFlag::RequiresMmap));
+
 	flags_ |= flags;
 
 	/* Import streams cannot be external. */
@@ -27,6 +36,9 @@ void Stream::setFlags(StreamFlags flags)
 
 void Stream::clearFlags(StreamFlags flags)
 {
+	/* We don't want dynamic mmapping. */
+	ASSERT(!(flags & StreamFlag::RequiresMmap));
+
 	flags_ &= ~flags;
 }
 
@@ -56,7 +68,7 @@ void Stream::resetBuffers()
 void Stream::setExportedBuffers(std::vector<std::unique_ptr<FrameBuffer>> *buffers)
 {
 	for (auto const &buffer : *buffers)
-		bufferMap_.emplace(++id_, buffer.get());
+		bufferEmplace(++id_, buffer.get());
 }
 
 const BufferMap &Stream::getBuffers() const
@@ -71,7 +83,7 @@ unsigned int Stream::getBufferId(FrameBuffer *buffer) const
 
 	/* Find the buffer in the map, and return the buffer id. */
 	auto it = std::find_if(bufferMap_.begin(), bufferMap_.end(),
-			       [&buffer](auto const &p) { return p.second == buffer; });
+			       [&buffer](auto const &p) { return p.second.buffer == buffer; });
 
 	if (it == bufferMap_.end())
 		return 0;
@@ -81,7 +93,7 @@ unsigned int Stream::getBufferId(FrameBuffer *buffer) const
 
 void Stream::setExportedBuffer(FrameBuffer *buffer)
 {
-	bufferMap_.emplace(++id_, buffer);
+	bufferEmplace(++id_, buffer);
 }
 
 int Stream::prepareBuffers(unsigned int count)
@@ -180,6 +192,27 @@ void Stream::returnBuffer(FrameBuffer *buffer)
 	}
 }
 
+const BufferObject &Stream::getBuffer(unsigned int id)
+{
+	auto const &it = bufferMap_.find(id);
+	if (it == bufferMap_.end())
+		return errorBufferObject;
+
+	return it->second;
+}
+
+const BufferObject &Stream::acquireBuffer()
+{
+	/* No id provided, so pick up the next available buffer if possible. */
+	if (availableBuffers_.empty())
+		return errorBufferObject;
+
+	unsigned int id = getBufferId(availableBuffers_.front());
+	availableBuffers_.pop();
+
+	return getBuffer(id);
+}
+
 int Stream::queueAllBuffers()
 {
 	int ret;
@@ -204,6 +237,16 @@ void Stream::releaseBuffers()
 	clearBuffers();
 }
 
+void Stream::bufferEmplace(unsigned int id, FrameBuffer *buffer)
+{
+	if (flags_ & StreamFlag::RequiresMmap)
+		bufferMap_.emplace(std::piecewise_construct, std::forward_as_tuple(id),
+				   std::forward_as_tuple(buffer, true));
+	else
+		bufferMap_.emplace(std::piecewise_construct, std::forward_as_tuple(id),
+				   std::forward_as_tuple(buffer, false));
+}
+
 void Stream::clearBuffers()
 {
 	availableBuffers_ = std::queue<FrameBuffer *>{};

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

@@ -7,22 +7,23 @@
 
 #pragma once
 
+#include <optional>
 #include <queue>
 #include <string>
 #include <unordered_map>
 #include <vector>
 
 #include <libcamera/base/flags.h>
+
 #include <libcamera/stream.h>
 
+#include "libcamera/internal/mapped_framebuffer.h"
 #include "libcamera/internal/v4l2_videodevice.h"
 
 namespace libcamera {
 
 namespace RPi {
 
-using BufferMap = std::unordered_map<unsigned int, FrameBuffer *>;
-
 enum BufferMask {
 	MaskID			= 0x00ffff,
 	MaskStats		= 0x010000,
@@ -30,6 +31,21 @@ enum BufferMask {
 	MaskBayerData		= 0x040000,
 };
 
+struct BufferObject {
+	BufferObject(FrameBuffer *b, bool requiresMmap)
+		: buffer(b), mapped(std::nullopt)
+	{
+		if (requiresMmap)
+			mapped = std::make_optional<MappedFrameBuffer>
+					(b, MappedFrameBuffer::MapFlag::ReadWrite);
+	}
+
+	FrameBuffer *buffer;
+	std::optional<MappedFrameBuffer> mapped;
+};
+
+using BufferMap = std::unordered_map<unsigned int, BufferObject>;
+
 /*
  * Device stream abstraction for either an internal or external stream.
  * Used for both Unicam and the ISP.
@@ -49,6 +65,11 @@ public:
 		 * buffers might be provided by (and returned to) the application.
 		 */
 		External	= (1 << 1),
+		/*
+		 * Indicates that the stream buffers need to be mmaped and returned
+		 * to the pipeline handler when requested.
+		 */
+		RequiresMmap	= (1 << 2),
 	};
 
 	using StreamFlags = Flags<StreamFlag>;
@@ -82,10 +103,17 @@ public:
 	int queueBuffer(FrameBuffer *buffer);
 	void returnBuffer(FrameBuffer *buffer);
 
+	const BufferObject &getBuffer(unsigned int id);
+	const BufferObject &acquireBuffer();
+
 	int queueAllBuffers();
 	void releaseBuffers();
 
+	/* For error handling. */
+	static const BufferObject errorBufferObject;
+
 private:
+	void bufferEmplace(unsigned int id, FrameBuffer *buffer);
 	void clearBuffers();
 	int queueToDevice(FrameBuffer *buffer);
 

src/libcamera/pipeline/rpi/vc4/vc4.cpp

@@ -825,7 +825,7 @@ void Vc4CameraData::processStatsComplete(const ipa::RPi::BufferIds &buffers)
 	if (!isRunning())
 		return;
 
-	FrameBuffer *buffer = isp_[Isp::Stats].getBuffers().at(buffers.stats & RPi::MaskID);
+	FrameBuffer *buffer = isp_[Isp::Stats].getBuffers().at(buffers.stats & RPi::MaskID).buffer;
 
 	handleStreamBuffer(buffer, &isp_[Isp::Stats]);
 
@@ -842,7 +842,7 @@ void Vc4CameraData::prepareIspComplete(const ipa::RPi::BufferIds &buffers)
 	if (!isRunning())
 		return;
 
-	buffer = unicam_[Unicam::Image].getBuffers().at(bayer & RPi::MaskID);
+	buffer = unicam_[Unicam::Image].getBuffers().at(bayer & RPi::MaskID).buffer;
 	LOG(RPI, Debug) << "Input re-queue to ISP, buffer id " << (bayer & RPi::MaskID)
 			<< ", timestamp: " << buffer->metadata().timestamp;
 
@@ -850,7 +850,7 @@ void Vc4CameraData::prepareIspComplete(const ipa::RPi::BufferIds &buffers)
 	ispOutputCount_ = 0;
 
 	if (sensorMetadata_ && embeddedId) {
-		buffer = unicam_[Unicam::Embedded].getBuffers().at(embeddedId & RPi::MaskID);
+		buffer = unicam_[Unicam::Embedded].getBuffers().at(embeddedId & RPi::MaskID).buffer;
 		handleStreamBuffer(buffer, &unicam_[Unicam::Embedded]);
 	}