qapi: Convert simple union ImageInfoSpecific to flat one

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 ImageInfoSpecific
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.

Implicit enum ImageInfoSpecificKind becomes explicit.  It duplicates
part of enum BlockdevDriver.  We could reuse BlockdevDriver instead.

Cc: Kevin Wolf <kwolf@redhat.com>
Cc: Hanna Reitz <hreitz@redhat.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Acked-by: Hanna Reitz <hreitz@redhat.com>
Message-Id: <20210917143134.412106-10-armbru@redhat.com>

diff --git a/qapi/block-core.json b/qapi/block-core.json
index c8ce1d9d5d8992ec0b80ca08c884c869c992e12d..623a4f4a3f3ab5c5726328b1b8d5dea7da8e4b40 100644 (file)
--- a/qapi/block-core.json
+++ b/qapi/block-core.json
@@ -139,6 +139,52 @@
       '*encryption-format': 'RbdImageEncryptionFormat'
   } }
 
+##
+# @ImageInfoSpecificKind:
+#
+# @luks: Since 2.7
+# @rbd: Since 6.1
+#
+# Since: 1.7
+##
+{ 'enum': 'ImageInfoSpecificKind',
+  'data': [ 'qcow2', 'vmdk', 'luks', 'rbd' ] }
+
+##
+# @ImageInfoSpecificQCow2Wrapper:
+#
+# Since: 1.7
+##
+{ 'struct': 'ImageInfoSpecificQCow2Wrapper',
+  'data': { 'data': 'ImageInfoSpecificQCow2' } }
+
+##
+# @ImageInfoSpecificVmdkWrapper:
+#
+# Since: 6.1
+##
+{ 'struct': 'ImageInfoSpecificVmdkWrapper',
+  'data': { 'data': 'ImageInfoSpecificVmdk' } }
+
+##
+# @ImageInfoSpecificLUKSWrapper:
+#
+# Since: 2.7
+##
+{ 'struct': 'ImageInfoSpecificLUKSWrapper',
+  'data': { 'data': 'QCryptoBlockInfoLUKS' } }
+# If we need to add block driver specific parameters for
+# LUKS in future, then we'll subclass QCryptoBlockInfoLUKS
+# to define a ImageInfoSpecificLUKS
+
+##
+# @ImageInfoSpecificRbdWrapper:
+#
+# Since: 6.1
+##
+{ 'struct': 'ImageInfoSpecificRbdWrapper',
+  'data': { 'data': 'ImageInfoSpecificRbd' } }
+
 ##
 # @ImageInfoSpecific:
 #
@@ -147,14 +193,13 @@
 # Since: 1.7
 ##
 { 'union': 'ImageInfoSpecific',
+  'base': { 'type': 'ImageInfoSpecificKind' },
+  'discriminator': 'type',
   'data': {
-      'qcow2': 'ImageInfoSpecificQCow2',
-      'vmdk': 'ImageInfoSpecificVmdk',
-      # If we need to add block driver specific parameters for
-      # LUKS in future, then we'll subclass QCryptoBlockInfoLUKS
-      # to define a ImageInfoSpecificLUKS
-      'luks': 'QCryptoBlockInfoLUKS',
-      'rbd': 'ImageInfoSpecificRbd'
+      'qcow2': 'ImageInfoSpecificQCow2Wrapper',
+      'vmdk': 'ImageInfoSpecificVmdkWrapper',
+      'luks': 'ImageInfoSpecificLUKSWrapper',
+      'rbd': 'ImageInfoSpecificRbdWrapper'
   } }
 
 ##