libcamera: add DmaBufAllocator::exportBuffers()

Add a helper function exportBuffers in DmaBufAllocator to make it easier
to use.

It'll be used in Virtual Pipeline Handler and SoftwareIsp.

Signed-off-by: Harvey Yang <chenghaoyang@chromium.org>
Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
Reviewed-by: Jacopo Mondi <jacopo.mondi@ideasonboard.com>
Signed-off-by: Kieran Bingham <kieran.bingham@ideasonboard.com>

include/libcamera/internal/dma_buf_allocator.h

@@ -7,11 +7,17 @@
 
 #pragma once
 
+#include <memory>
+#include <string>
+#include <vector>
+
 #include <libcamera/base/flags.h>
 #include <libcamera/base/unique_fd.h>
 
 namespace libcamera {
 
+class FrameBuffer;
+
 class DmaBufAllocator
 {
 public:
@@ -28,7 +34,14 @@ public:
 	bool isValid() const { return providerHandle_.isValid(); }
 	UniqueFD alloc(const char *name, std::size_t size);
 
+	int exportBuffers(unsigned int count,
+			  const std::vector<unsigned int> &planeSizes,
+			  std::vector<std::unique_ptr<FrameBuffer>> *buffers);
+
 private:
+	std::unique_ptr<FrameBuffer> createBuffer(
+		std::string name, const std::vector<unsigned int> &planeSizes);
+
 	UniqueFD allocFromHeap(const char *name, std::size_t size);
 	UniqueFD allocFromUDmaBuf(const char *name, std::size_t size);
 	UniqueFD providerHandle_;

src/libcamera/dma_buf_allocator.cpp

@@ -22,6 +22,9 @@
 
 #include <libcamera/base/log.h>
 #include <libcamera/base/memfd.h>
+#include <libcamera/base/shared_fd.h>
+
+#include <libcamera/framebuffer.h>
 
 /**
  * \file dma_buf_allocator.cpp
@@ -205,4 +208,58 @@ UniqueFD DmaBufAllocator::alloc(const char *name, std::size_t size)
 		return allocFromHeap(name, size);
 }
 
+/**
+ * \brief Allocate and export buffers from the DmaBufAllocator
+ * \param[in] count The number of requested FrameBuffers
+ * \param[in] planeSizes The sizes of planes in each FrameBuffer
+ * \param[out] buffers Array of buffers successfully allocated
+ *
+ * Planes in a FrameBuffer are allocated with a single dma buf.
+ * \todo Add the option to allocate each plane with a dma buf respectively.
+ *
+ * \return The number of allocated buffers on success or a negative error code
+ * otherwise
+ */
+int DmaBufAllocator::exportBuffers(unsigned int count,
+				   const std::vector<unsigned int> &planeSizes,
+				   std::vector<std::unique_ptr<FrameBuffer>> *buffers)
+{
+	for (unsigned int i = 0; i < count; ++i) {
+		std::unique_ptr<FrameBuffer> buffer =
+			createBuffer("frame-" + std::to_string(i), planeSizes);
+		if (!buffer) {
+			LOG(DmaBufAllocator, Error) << "Unable to create buffer";
+
+			buffers->clear();
+			return -EINVAL;
+		}
+
+		buffers->push_back(std::move(buffer));
+	}
+
+	return count;
+}
+
+std::unique_ptr<FrameBuffer>
+DmaBufAllocator::createBuffer(std::string name,
+			      const std::vector<unsigned int> &planeSizes)
+{
+	std::vector<FrameBuffer::Plane> planes;
+
+	unsigned int frameSize = 0, offset = 0;
+	for (auto planeSize : planeSizes)
+		frameSize += planeSize;
+
+	SharedFD fd(alloc(name.c_str(), frameSize));
+	if (!fd.isValid())
+		return nullptr;
+
+	for (auto planeSize : planeSizes) {
+		planes.emplace_back(FrameBuffer::Plane{ fd, offset, planeSize });
+		offset += planeSize;
+	}
+
+	return std::make_unique<FrameBuffer>(planes);
+}
+
 } /* namespace libcamera */