diff --git a/include/uapi/linux/nbd.h b/include/uapi/linux/nbd.h
index 20d6cc91435df..8797387caaf73 100644
--- a/include/uapi/linux/nbd.h
+++ b/include/uapi/linux/nbd.h
@@ -11,6 +11,8 @@
  *            Cleanup PARANOIA usage & code.
  * 2004/02/19 Paul Clements
  *            Removed PARANOIA, plus various cleanup and comments
+ * 2023 Copyright Red Hat
+ *            Link to userspace extensions.
  */
 
 #ifndef _UAPILINUX_NBD_H
@@ -30,12 +32,18 @@
 #define NBD_SET_TIMEOUT _IO( 0xab, 9 )
 #define NBD_SET_FLAGS   _IO( 0xab, 10)
 
+/*
+ * See also https://github.com/NetworkBlockDevice/nbd/blob/master/doc/proto.md
+ * for additional userspace extensions not yet utilized in the kernel module.
+ */
+
 enum {
 	NBD_CMD_READ = 0,
 	NBD_CMD_WRITE = 1,
 	NBD_CMD_DISC = 2,
 	NBD_CMD_FLUSH = 3,
 	NBD_CMD_TRIM = 4
+	/* userspace defines additional extension commands */
 };
 
 /* values for flags field, these are server interaction specific. */
@@ -64,14 +72,15 @@ enum {
 #define NBD_REQUEST_MAGIC 0x25609513
 #define NBD_REPLY_MAGIC 0x67446698
 /* Do *not* use magics: 0x12560953 0x96744668. */
+/* magic 0x668e33ef for structured reply not supported by kernel yet */
 
 /*
  * This is the packet used for communication between client and
  * server. All data are in network byte order.
  */
 struct nbd_request {
-	__be32 magic;
-	__be32 type;	/* == READ || == WRITE 	*/
+	__be32 magic;	/* NBD_REQUEST_MAGIC	*/
+	__be32 type;	/* See NBD_CMD_*	*/
 	char handle[8];
 	__be64 from;
 	__be32 len;
@@ -82,7 +91,7 @@ struct nbd_request {
  * it has completed an I/O request (or an error occurs).
  */
 struct nbd_reply {
-	__be32 magic;
+	__be32 magic;		/* NBD_REPLY_MAGIC	*/
 	__be32 error;		/* 0 = ok, else error	*/
 	char handle[8];		/* handle you got from request	*/
 };