libcamera: buffer: Add an accessor to the BufferMemory

Buffer instances reference memory, which is modelled internally by a
BufferMemory instance. Store a pointer to the BufferMemory in the Buffer
class, and populate it when the buffer is queued to the camera through a
request. This is useful for applications to access the buffer memory in
the buffer or request completion handler.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Niklas Söderlund <niklas.soderlund@ragnatech.se>

2 files changed, 15 insertions, 0 deletions

diff --git a/src/libcamera/buffer.cpp b/src/libcamera/buffer.cpp
index 99358633..fe29c2f6 100644
--- a/src/libcamera/buffer.cpp
+++ b/src/libcamera/buffer.cpp
@@ -301,6 +301,17 @@ Buffer::Buffer(unsigned int index, const Buffer *metadata)
  */
 
 /**
+ * \fn Buffer::mem()
+ * \brief Retrieve the BufferMemory this buffer is associated with
+ *
+ * The association between the buffer and a BufferMemory instance is valid from
+ * the time the request containing this buffer is queued to a camera to the end
+ * of that request's completion handler.
+ *
+ * \return The BufferMemory this buffer is associated with
+ */
+
+/**
  * \fn Buffer::bytesused()
  * \brief Retrieve the number of bytes occupied by the data in the buffer
  * \return Number of bytes occupied in the buffer
diff --git a/src/libcamera/camera.cpp b/src/libcamera/camera.cpp
index af69607b..db15fd46 100644
--- a/src/libcamera/camera.cpp
+++ b/src/libcamera/camera.cpp
@@ -811,10 +811,14 @@ int Camera::queueRequest(Request *request)
 
 	for (auto const &it : request->buffers()) {
 		Stream *stream = it.first;
+		Buffer *buffer = it.second;
+
 		if (activeStreams_.find(stream) == activeStreams_.end()) {
 			LOG(Camera, Error) << "Invalid request";
 			return -EINVAL;
 		}
+
+		buffer->mem_ = &stream->buffers()[buffer->index_];
 	}
 
 	int ret = request->prepare();