[libcamera-devel] [PATCH 3/9] libcamera: pipeline: Support external buffers

[Jacopo Mondi]

Add support for use external buffers to libcamera pipeline handlers.

Use the memory type flag in pipeline handlers (todo: change all pipeline
handlers) during buffer setup operations, to decide if the Stream's
internal memory has to be exported to applications, or the Stream
should prepare to use buffers whose memory is allocated elsewhere.

To support the last use case, a translation mechanism between the external
buffers provided by applications and internal ones used by pipeline
handlers to feed the video device will be implemented on top of this
change.

Signed-off-by: Jacopo Mondi <jacopo at jmondi.org>
---
 src/libcamera/pipeline/ipu3/ipu3.cpp     | 31 +++++++++++++++++++++++-
 src/libcamera/pipeline/rkisp1/rkisp1.cpp |  9 ++++++-
 src/libcamera/pipeline/uvcvideo.cpp      |  8 +++++-
 src/libcamera/pipeline/vimc.cpp          |  8 +++++-
 4 files changed, 52 insertions(+), 4 deletions(-)

diff --git a/src/libcamera/pipeline/ipu3/ipu3.cpp b/src/libcamera/pipeline/ipu3/ipu3.cpp
index 2de0892138a8..6f14da1f8c70 100644
--- a/src/libcamera/pipeline/ipu3/ipu3.cpp
+++ b/src/libcamera/pipeline/ipu3/ipu3.cpp
@@ -71,6 +71,7 @@ public:
 
 	int importBuffers(BufferPool *pool);
 	int exportBuffers(ImgUOutput *output, BufferPool *pool);
+	int reserveDmabufBuffers(ImgUOutput *output, BufferPool *pool);
 	void freeBuffers();
 
 	int start();
@@ -624,7 +625,11 @@ int PipelineHandlerIPU3::allocateBuffers(Camera *camera,
 		IPU3Stream *stream = static_cast<IPU3Stream *>(s);
 		ImgUDevice::ImgUOutput *dev = stream->device_;
 
-		ret = imgu->exportBuffers(dev, &stream->bufferPool());
+		if (stream->memoryType() == ExternalMemory)
+			ret = imgu->reserveDmabufBuffers(dev,
+							 &stream->bufferPool());
+		else
+			ret = imgu->exportBuffers(dev, &stream->bufferPool());
 		if (ret)
 			goto error;
 	}
@@ -1153,6 +1158,30 @@ int ImgUDevice::exportBuffers(ImgUOutput *output, BufferPool *pool)
 	return 0;
 }
 
+/**
+ * \brief Reserve buffers in \a output from the provided \a pool
+ * \param[in] output The ImgU output device
+ * \param[in] pool The buffer pool used to reserve buffers in \a output
+ *
+ * Reserve a number of buffers equal to the number of buffers in \a pool
+ * in the \a output device to prepare for streaming operations using buffers
+ * whose memory has been reserved elsewhere identified with DMABUF file
+ * descriptors.
+ *
+ * \return 0 on success or a negative error code otherwise
+ */
+int ImgUDevice::reserveDmabufBuffers(ImgUOutput *output, BufferPool *pool)
+{
+	int ret = output->dev->importBuffers(pool);
+	if (ret) {
+		LOG(IPU3, Error) << "Failed to import buffer in "
+				 << output->name << " ImgU device";
+		return ret;
+	}
+
+	return 0;
+}
+
 /**
  * \brief Release buffers for all the ImgU video devices
  */
diff --git a/src/libcamera/pipeline/rkisp1/rkisp1.cpp b/src/libcamera/pipeline/rkisp1/rkisp1.cpp
index 4a5898d25f91..dbb61a21354d 100644
--- a/src/libcamera/pipeline/rkisp1/rkisp1.cpp
+++ b/src/libcamera/pipeline/rkisp1/rkisp1.cpp
@@ -319,7 +319,14 @@ int PipelineHandlerRkISP1::allocateBuffers(Camera *camera,
 					   const std::set<Stream *> &streams)
 {
 	Stream *stream = *streams.begin();
-	return video_->exportBuffers(&stream->bufferPool());
+	int ret;
+
+	if (stream->memoryType() == InternalMemory)
+		ret = video_->exportBuffers(&stream->bufferPool());
+	else
+		ret = video_->importBuffers(&stream->bufferPool());
+
+	return ret;
 }
 
 int PipelineHandlerRkISP1::freeBuffers(Camera *camera,
diff --git a/src/libcamera/pipeline/uvcvideo.cpp b/src/libcamera/pipeline/uvcvideo.cpp
index 72313cfd246f..5b3c79dda6dd 100644
--- a/src/libcamera/pipeline/uvcvideo.cpp
+++ b/src/libcamera/pipeline/uvcvideo.cpp
@@ -197,10 +197,16 @@ int PipelineHandlerUVC::allocateBuffers(Camera *camera,
 	UVCCameraData *data = cameraData(camera);
 	Stream *stream = *streams.begin();
 	const StreamConfiguration &cfg = stream->configuration();
+	int ret;
 
 	LOG(UVC, Debug) << "Requesting " << cfg.bufferCount << " buffers";
 
-	return data->video_->exportBuffers(&stream->bufferPool());
+	if (stream->memoryType() == InternalMemory)
+		ret = data->video_->exportBuffers(&stream->bufferPool());
+	else
+		ret = data->video_->importBuffers(&stream->bufferPool());
+
+	return ret;
 }
 
 int PipelineHandlerUVC::freeBuffers(Camera *camera,
diff --git a/src/libcamera/pipeline/vimc.cpp b/src/libcamera/pipeline/vimc.cpp
index f8a58be060bb..c67bdb0ecbff 100644
--- a/src/libcamera/pipeline/vimc.cpp
+++ b/src/libcamera/pipeline/vimc.cpp
@@ -199,10 +199,16 @@ int PipelineHandlerVimc::allocateBuffers(Camera *camera,
 	VimcCameraData *data = cameraData(camera);
 	Stream *stream = *streams.begin();
 	const StreamConfiguration &cfg = stream->configuration();
+	int ret;
 
 	LOG(VIMC, Debug) << "Requesting " << cfg.bufferCount << " buffers";
 
-	return data->video_->exportBuffers(&stream->bufferPool());
+	if (stream->memoryType() == InternalMemory)
+		ret = data->video_->exportBuffers(&stream->bufferPool());
+	else
+		ret = data->video_->importBuffers(&stream->bufferPool());
+
+	return ret;
 }
 
 int PipelineHandlerVimc::freeBuffers(Camera *camera,
-- 
2.21.0