[libcamera-devel] [PATCH v5 08/14] libcamera: buffer: Store Request reference in Buffer

[Jacopo Mondi]

Add to the Buffer class methods to set and retrieve a reference to the
Request instance the buffer is part of.

As buffers might outlive the Request they are associated with, the
reference is only temporary valid during the buffer completion interval
(from when the buffer gets queued to Camera for processing, until it
gets marked as completed).

Signed-off-by: Jacopo Mondi <jacopo at jmondi.org>
---
 include/libcamera/buffer.h |  6 ++++++
 src/libcamera/buffer.cpp   | 25 ++++++++++++++++++++++++-
 src/libcamera/request.cpp  |  3 +++
 3 files changed, 33 insertions(+), 1 deletion(-)

diff --git a/include/libcamera/buffer.h b/include/libcamera/buffer.h
index 0c844d126a27..8f9b42e39339 100644
--- a/include/libcamera/buffer.h
+++ b/include/libcamera/buffer.h
@@ -13,6 +13,7 @@
 namespace libcamera {
 
 class BufferPool;
+class Request;
 
 class Plane final
 {
@@ -52,14 +53,18 @@ public:
 	unsigned int sequence() const { return sequence_; }
 	Status status() const { return status_; }
 	std::vector<Plane> &planes() { return planes_; }
+	Request *request() const { return request_; }
 
 private:
 	friend class BufferPool;
 	friend class PipelineHandler;
+	friend class Request;
 	friend class V4L2Device;
 
 	void cancel();
 
+	void setRequest(Request *request) { request_ = request; }
+
 	unsigned int index_;
 	unsigned int bytesused_;
 	uint64_t timestamp_;
@@ -67,6 +72,7 @@ private:
 	Status status_;
 
 	std::vector<Plane> planes_;
+	Request *request_;
 };
 
 class BufferPool final
diff --git a/src/libcamera/buffer.cpp b/src/libcamera/buffer.cpp
index e2d1cf04411e..8261ca41d62e 100644
--- a/src/libcamera/buffer.cpp
+++ b/src/libcamera/buffer.cpp
@@ -196,7 +196,7 @@ void *Plane::mem()
  */
 
 Buffer::Buffer()
-	: index_(-1)
+	: index_(-1), request_(nullptr)
 {
 }
 
@@ -248,6 +248,22 @@ Buffer::Buffer()
  * \return The buffer status
  */
 
+/**
+ * \fn Buffer::request()
+ * \brief Retrieve the request this buffer belongs to
+ *
+ * The intended callers of this method are buffer completion handlers that
+ * needs to associate a buffer to the request it belongs to.
+ *
+ * A Buffer is associated to a request by Request::prepare() and the
+ * association is valid until the buffer completes. The returned request
+ * pointer is valid only during that interval.
+ *
+ * \return The Request the Buffer belongs to, or nullptr if the buffer is
+ * either completed or not associated with a request
+ * \sa Buffer::setRequest()
+ */
+
 /**
  * \brief Mark a buffer as cancel by setting its status to BufferCancelled
  */
@@ -259,6 +275,13 @@ void Buffer::cancel()
 	status_ = BufferCancelled;
 }
 
+/**
+ * \fn Buffer::setRequest()
+ * \brief Set the request this buffer belongs to
+ *
+ * The intended callers are Request::prepare() and Request::completeBuffer().
+ */
+
 /**
  * \class BufferPool
  * \brief A pool of buffers
diff --git a/src/libcamera/request.cpp b/src/libcamera/request.cpp
index c429d1fb2f8a..855da7c245e9 100644
--- a/src/libcamera/request.cpp
+++ b/src/libcamera/request.cpp
@@ -136,6 +136,7 @@ int Request::prepare()
 {
 	for (auto const &pair : bufferMap_) {
 		Buffer *buffer = pair.second;
+		buffer->setRequest(this);
 		pending_.insert(buffer);
 	}
 
@@ -177,6 +178,8 @@ bool Request::completeBuffer(Buffer *buffer)
 	int ret = pending_.erase(buffer);
 	ASSERT(ret == 1);
 
+	buffer->setRequest(nullptr);
+
 	return !hasPendingBuffers();
 }
 
-- 
2.21.0