[PULL 06/25] qapi: Convert simple union MemoryDeviceInfo to flat one

[Markus Armbruster]

Simple unions predate flat unions.  Having both complicates the QAPI
schema language and the QAPI generator.  We haven't been using simple
unions in new code for a long time, because they are less flexible and
somewhat awkward on the wire.

To prepare for their removal, convert simple union MemoryDeviceInfo to
an equivalent flat one.  Adds some boilerplate to the schema, which is
a bit ugly, but a lot easier to maintain than the simple union
feature.

Cc: Eduardo Habkost <ehabkost@redhat.com>
Cc: Marcel Apfelbaum <marcel.apfelbaum@gmail.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-Id: <20210917143134.412106-7-armbru@redhat.com>
---
 qapi/machine.json | 42 ++++++++++++++++++++++++++++++++++++++----
 1 file changed, 38 insertions(+), 4 deletions(-)

diff --git a/qapi/machine.json b/qapi/machine.json
index 157712f006..32d47f4e35 100644
--- a/qapi/machine.json
+++ b/qapi/machine.json
@@ -1194,6 +1194,38 @@
           }
 }
 
+##
+# @MemoryDeviceInfoKind:
+#
+# Since: 2.1
+##
+{ 'enum': 'MemoryDeviceInfoKind',
+  'data': [ 'dimm', 'nvdimm', 'virtio-pmem', 'virtio-mem' ] }
+
+##
+# @PCDIMMDeviceInfoWrapper:
+#
+# Since: 2.1
+##
+{ 'struct': 'PCDIMMDeviceInfoWrapper',
+  'data': { 'data': 'PCDIMMDeviceInfo' } }
+
+##
+# @VirtioPMEMDeviceInfoWrapper:
+#
+# Since: 2.1
+##
+{ 'struct': 'VirtioPMEMDeviceInfoWrapper',
+  'data': { 'data': 'VirtioPMEMDeviceInfo' } }
+
+##
+# @VirtioMEMDeviceInfoWrapper:
+#
+# Since: 2.1
+##
+{ 'struct': 'VirtioMEMDeviceInfoWrapper',
+  'data': { 'data': 'VirtioMEMDeviceInfo' } }
+
 ##
 # @MemoryDeviceInfo:
 #
@@ -1205,10 +1237,12 @@
 # Since: 2.1
 ##
 { 'union': 'MemoryDeviceInfo',
-  'data': { 'dimm': 'PCDIMMDeviceInfo',
-            'nvdimm': 'PCDIMMDeviceInfo',
-            'virtio-pmem': 'VirtioPMEMDeviceInfo',
-            'virtio-mem': 'VirtioMEMDeviceInfo'
+  'base': { 'type': 'MemoryDeviceInfoKind' },
+  'discriminator': 'type',
+  'data': { 'dimm': 'PCDIMMDeviceInfoWrapper',
+            'nvdimm': 'PCDIMMDeviceInfoWrapper',
+            'virtio-pmem': 'VirtioPMEMDeviceInfoWrapper',
+            'virtio-mem': 'VirtioMEMDeviceInfoWrapper'
           }
 }
 
-- 
2.31.1