qapi-schema: Collect migration stuff in qapi/migration.json

Cc: Juan Quintela <quintela@redhat.com>
Cc: Dr. David Alan Gilbert <dgilbert@redhat.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Message-Id: <1503602048-12268-10-git-send-email-armbru@redhat.com>
Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>

1 files changed, 16 insertions, 0 deletions

diff --git a/qapi/common.json b/qapi/common.json
index 862e73f982..e2c58564d8 100644
--- a/qapi/common.json
+++ b/qapi/common.json
@@ -173,3 +173,19 @@
 { 'struct': 'String',
   'data': {
     'str': 'str' } }
+
+##
+# @StrOrNull:
+#
+# This is a string value or the explicit lack of a string (null
+# pointer in C).  Intended for cases when 'optional absent' already
+# has a different meaning.
+#
+# @s: the string value
+# @n: no string value
+#
+# Since: 2.10
+##
+{ 'alternate': 'StrOrNull',
+  'data': { 's': 'str',
+            'n': 'null' } }