qapi/qom: Add ObjectOptions for iothread

Add an ObjectOptions union that will eventually describe the options of
all user creatable object types. As unions can't exist without any
branches, also add the first object type.

This adds a QAPI schema for the properties of the iothread object.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Acked-by: Paolo Bonzini <pbonzini@redhat.com>
Acked-by: Peter Krempa <pkrempa@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>

qapi/qom.json

@@ -202,6 +202,59 @@
   'returns': [ 'ObjectPropertyInfo' ],
   'allow-preconfig': true }
 
+##
+# @IothreadProperties:
+#
+# Properties for iothread objects.
+#
+# @poll-max-ns: the maximum number of nanoseconds to busy wait for events.
+#               0 means polling is disabled (default: 32768 on POSIX hosts,
+#               0 otherwise)
+#
+# @poll-grow: the multiplier used to increase the polling time when the
+#             algorithm detects it is missing events due to not polling long
+#             enough. 0 selects a default behaviour (default: 0)
+#
+# @poll-shrink: the divisor used to decrease the polling time when the
+#               algorithm detects it is spending too long polling without
+#               encountering events. 0 selects a default behaviour (default: 0)
+#
+# Since: 2.0
+##
+{ 'struct': 'IothreadProperties',
+  'data': { '*poll-max-ns': 'int',
+            '*poll-grow': 'int',
+            '*poll-shrink': 'int' } }
+
+##
+# @ObjectType:
+#
+# Since: 6.0
+##
+{ 'enum': 'ObjectType',
+  'data': [
+    'iothread'
+  ] }
+
+##
+# @ObjectOptions:
+#
+# Describes the options of a user creatable QOM object.
+#
+# @qom-type: the class name for the object to be created
+#
+# @id: the name of the new object
+#
+# Since: 6.0
+##
+{ 'union': 'ObjectOptions',
+  'base': { 'qom-type': 'ObjectType',
+            'id': 'str' },
+  'discriminator': 'qom-type',
+  'data': {
+      'iothread':                   'IothreadProperties'
+  } }
+
 ##
 # @object-add:
 #