3 files changed, 33 insertions, 1 deletions

diff --git a/include/libcamera/buffer.h b/include/libcamera/buffer.h
index 0c844d12..8f9b42e3 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 e2d1cf04..21abdcce 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)
 {
 }
 
@@ -249,6 +249,22 @@ Buffer::Buffer()
  */
 
 /**
+ * \fn Buffer::request()
+ * \brief Retrieve the request this buffer belongs to
+ *
+ * The intended callers of this method are buffer completion handlers that
+ * need 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
  */
 void Buffer::cancel()
@@ -260,6 +276,13 @@ void Buffer::cancel()
 }
 
 /**
+ * \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 7088a479..433c6f83 100644
--- a/src/libcamera/request.cpp
+++ b/src/libcamera/request.cpp
@@ -141,6 +141,7 @@ 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();
 }