[PATCH RFC v7 7/8] admin: document that structures can be shorter or longer

["Michael S. Tsirkin" <mst@redhat.com>]

ensures forward and backward compatibility as long as
we tuck new structures at the end.

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
---
 admin.tex | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/admin.tex b/admin.tex
index a0008c7..99b6c2a 100644
--- a/admin.tex
+++ b/admin.tex
@@ -136,6 +136,12 @@ \subsection{Group administration commands}\label{sec:Basic Facilities of a Virti
 holds the command specific error. If \field{status} is not set to VIRTIO_ADMIN_STATUS_CS_ERR, the
 \field{command_specific_error} value is undefined and should be ignored by the driver.
 
+It is legal for the driver to submit commands with device-writeable and
+device-readable structures both shorter and longer than what
+is described in this specification. Device silently truncates the
+structures to the shorter of the two (submitted by driver and
+described in this specification).
+
 \section{Administration Virtqueue}\label{sec:Basic Facilities of a Virtio Device / Group Administration Virtqueues}
 
 An administration virtqueue of a parent device is used to submit
-- 
MST