libcamera: v4l2_device: Update dequeued buffer information

Copy the information from the struct v4l2_buffer when dequeueing the
buffer as applications need this information to make sense of the
captured data.

Signed-off-by: Niklas Söderlund <niklas.soderlund@ragnatech.se>
Signed-off-by: Jacopo Mondi <jacopo@jmondi.org>
Signed-off-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

src/libcamera/buffer.cpp

@@ -203,6 +203,32 @@ Buffer::Buffer()
  * \brief A Signal to provide notifications that the specific Buffer is ready
  */
 
+/**
+ * \fn Buffer::bytesused()
+ * \brief Retrieve the number of bytes occupied by the data in the buffer
+ * \return Number of bytes occupied in the buffer
+ */
+
+/**
+ * \fn Buffer::timestamp()
+ * \brief Retrieve the time when the buffer was processed
+ *
+ * The timestamp is expressed as a number number of nanoseconds since the epoch.
+ *
+ * \return Timestamp when the buffer was processed
+ */
+
+/**
+ * \fn Buffer::sequence()
+ * \brief Retrieve the buffer sequence number
+ *
+ * The sequence number is a monotonically increasing number assigned to the
+ * buffer processed by the stream. Gaps in the sequence numbers indicate
+ * dropped frames.
+ *
+ * \return Sequence number of the buffer
+ */
+
 /**
  * \class BufferPool
  * \brief A pool of buffers