spapr_drc: Expose 'null' in qom-get when there is no fdt

Now that the QMP output visitor supports an explicit null
output, we should utilize it to make it easier to diagnose
the difference between a missing fdt ('null') vs. a
present-but-empty one ('{}').

(Note that this reverts the behavior of commit ab8bf1d, taking
us back to the behavior of commit 6c2f9a1 [which in turn
stemmed from a crash fix in 1d10b44]; but that this time,
the change is intentional and not an accidental side-effect.)

Signed-off-by: Eric Blake <eblake@redhat.com>
Acked-by: David Gibson <david@gibson.dropbear.id.au>
Message-Id: <1461879932-9020-17-git-send-email-eblake@redhat.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>

diff --git a/hw/ppc/spapr_drc.c b/hw/ppc/spapr_drc.c
index 1f5f1d790ac84b8fad9da36fb3fd94c953fc3566..480a8c607c3e5433e5892accdb0a20b1ccfda335 100644 (file)
--- a/hw/ppc/spapr_drc.c
+++ b/hw/ppc/spapr_drc.c
@@ -269,11 +269,7 @@ static void prop_get_fdt(Object *obj, Visitor *v, const char *name,
     void *fdt;
 
     if (!drc->fdt) {
-        visit_start_struct(v, name, NULL, 0, &err);
-        if (!err) {
-            visit_end_struct(v, &err);
-        }
-        error_propagate(errp, err);
+        visit_type_null(v, NULL, errp);
         return;
     }