[libcamera-devel] [RFC 08/12] libcamera: buffer: Add a buffer allocator

[Niklas Söderlund]

>From an applications point of view buffers shall not be allocated
directly by a camera or stream. Instead they shall be allocated
externally and used by a camera.

To model this behavior add a buffer allocator that is exposed to
applications. How the allocator creates buffers is pipeline specific and
handled by sub-classing the stream class.

Signed-off-by: Niklas Söderlund <niklas.soderlund at ragnatech.se>
---
 include/libcamera/buffer.h | 17 ++++++++++++++
 include/libcamera/stream.h |  1 +
 src/libcamera/buffer.cpp   | 48 ++++++++++++++++++++++++++++++++++++++
 3 files changed, 66 insertions(+)

diff --git a/include/libcamera/buffer.h b/include/libcamera/buffer.h
index c626f669040b3c04..adb642ad5da072d2 100644
--- a/include/libcamera/buffer.h
+++ b/include/libcamera/buffer.h
@@ -8,11 +8,14 @@
 #define __LIBCAMERA_BUFFER_H__
 
 #include <array>
+#include <map>
+#include <memory>
 #include <stdint.h>
 #include <vector>
 
 namespace libcamera {
 
+class Camera;
 class Request;
 class Stream;
 
@@ -139,6 +142,20 @@ private:
 	std::vector<PlaneInfo> planes_;
 };
 
+class BufferAllocator
+{
+public:
+	BufferAllocator(std::shared_ptr<Camera> camera);
+	~BufferAllocator();
+
+	int allocate(Stream *stream);
+	std::vector<Buffer *> get(Stream *stream);
+
+private:
+	std::shared_ptr<Camera> camera_;
+	std::map<Stream *, std::vector<Buffer *>> allocated_;
+};
+
 } /* namespace libcamera */
 
 #endif /* __LIBCAMERA_BUFFER_H__ */
diff --git a/include/libcamera/stream.h b/include/libcamera/stream.h
index dac4831cfa1a9b1d..b051341511a7ab7c 100644
--- a/include/libcamera/stream.h
+++ b/include/libcamera/stream.h
@@ -84,6 +84,7 @@ public:
 	MemoryType memoryType() const { return memoryType_; }
 
 protected:
+	friend class BufferAllocator;
 	friend class Camera;
 
 	virtual int allocateBuffers(std::vector<Buffer *> *buffers) { return -EINVAL; }
diff --git a/src/libcamera/buffer.cpp b/src/libcamera/buffer.cpp
index 10b16a862393b536..fce1ce5e49cbbf42 100644
--- a/src/libcamera/buffer.cpp
+++ b/src/libcamera/buffer.cpp
@@ -12,6 +12,9 @@
 #include <sys/mman.h>
 #include <unistd.h>
 
+#include <libcamera/camera.h>
+#include <libcamera/stream.h>
+
 #include "log.h"
 
 /**
@@ -393,4 +396,49 @@ void Buffer::cancel()
  * The intended callers are Request::prepare() and Request::completeBuffer().
  */
 
+BufferAllocator::BufferAllocator(std::shared_ptr<Camera> camera)
+	: camera_(camera)
+{
+}
+
+BufferAllocator::~BufferAllocator()
+{
+	for (auto &it : allocated_) {
+		Stream *stream = it.first;
+		std::vector<Buffer *> &buffers = it.second;
+
+		for (Buffer *buffer : buffers)
+			delete buffer;
+
+		buffers.clear();
+
+		stream->allocateBuffers(nullptr);
+	}
+}
+
+int BufferAllocator::allocate(Stream *stream)
+{
+	bool found = false;
+
+	for (const Stream *s : camera_->streams()) {
+		if (stream == s) {
+			found = true;
+			break;
+		}
+	}
+
+	if (!found)
+		return -EINVAL;
+
+	return stream->allocateBuffers(&allocated_[stream]);
+}
+
+std::vector<Buffer *> BufferAllocator::get(Stream *stream)
+{
+	if (allocated_.find(stream) == allocated_.end())
+		return {};
+
+	return allocated_[stream];
+}
+
 } /* namespace libcamera */
-- 
2.23.0