Make drive unit attribute optional in the XML schema

The "unit" attribute of a drive address is optional in the code, so should
also be in the XML schema.

Signed-off-by: Michael Ellerman <michael@ellerman.id.au>

diff --git a/docs/schemas/domaincommon.rng b/docs/schemas/domaincommon.rng
index db02603cd267a8b378d6609bf11b91904fc58ad7..6d265f3c2c71b06799fe78eaabec52b05fbf19d6 100644 (file)
--- a/docs/schemas/domaincommon.rng
+++ b/docs/schemas/domaincommon.rng
@@ -2320,9 +2320,11 @@
         <ref name="driveBus"/>
       </attribute>
     </optional>
-    <attribute name="unit">
-      <ref name="driveUnit"/>
-    </attribute>
+    <optional>
+      <attribute name="unit">
+        <ref name="driveUnit"/>
+      </attribute>
+    </optional>
   </define>
   <define name="virtioserialaddress">
     <attribute name="controller">