diff --git a/ccid/ccid_device.c b/ccid/ccid_device.c
index ffcbacc..f91abb8 100644
--- a/ccid/ccid_device.c
+++ b/ccid/ccid_device.c
@@ -617,7 +617,9 @@
 
 /*! Handle data arriving from the host on the OUT endpoint.
  *  \param[in] cs CCID Instance on which to operate
- *  \param[in] msgb received message buffer containing one CCID OUT EP message from the host
+ *  \param[in] msgb received message buffer containing one CCID OUT EP message from the host.
+ *  		    Ownership of message buffer is transferred, i.e. it's our job to msgb_free()
+ *  		    it eventually, after we're done with it (could be asynchronously).
  *  \returns 0 on success; negative on error */
 int ccid_handle_out(struct ccid_instance *ci, struct msgb *msg)
 {
diff --git a/ccid/ccid_device.h b/ccid/ccid_device.h
index bc69523..d0fcdc0 100644
--- a/ccid/ccid_device.h
+++ b/ccid/ccid_device.h
@@ -59,6 +59,9 @@
 
 /* CCID operations */
 struct ccid_ops {
+	/* msgb ownership in below functions is transferred, i.e. whoever
+	 * provides the callback function must make sure to msgb_free() them
+	 * once transmission on IN or INT EP has completed. */
 	int (*send_in)(struct ccid_instance *ci, struct msgb *msg);
 	int (*send_int)(struct ccid_instance *ci, struct msgb *msg);
 };