[PATCH 07/22] qapi: Convert simple union ChardevBackend 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 ChardevBackend 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: "Marc-André Lureau" <marcandre.lureau@redhat.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>
---
 qapi/char.json | 169 +++++++++++++++++++++++++++++++++++++++++++------
 1 file changed, 148 insertions(+), 21 deletions(-)

diff --git a/qapi/char.json b/qapi/char.json
index 9b18ee3305..69c136c138 100644
--- a/qapi/char.json
+++ b/qapi/char.json
@@ -407,6 +407,131 @@
   'base': 'ChardevCommon',
   'if': 'CONFIG_SPICE_PROTOCOL' }
 
+##
+# @ChardevBackendKind:
+#
+# Since: 6.1
+##
+{ 'enum': 'ChardevBackendKind',
+  'data': [ 'file',
+            'serial',
+            'parallel',
+            'pipe',
+            'socket',
+            'udp',
+            'pty',
+            'null',
+            'mux',
+            'msmouse',
+            'wctablet',
+            'braille',
+            'testdev',
+            'stdio',
+            'console',
+            { 'name': 'spicevmc', 'if': 'CONFIG_SPICE' },
+            { 'name': 'spiceport', 'if': 'CONFIG_SPICE' },
+            { 'name': 'qemu-vdagent', 'if': 'CONFIG_SPICE_PROTOCOL' },
+            'vc',
+            'ringbuf',
+            # next one is just for compatibility
+            'memory' ] }
+
+##
+# @ChardevFileWrapper:
+#
+# Since: 6.1
+##
+{ 'struct': 'ChardevFileWrapper',
+  'data': { 'data': 'ChardevFile' } }
+
+##
+# @ChardevHostdevWrapper:
+#
+# Since: 6.1
+##
+{ 'struct': 'ChardevHostdevWrapper',
+  'data': { 'data': 'ChardevHostdev' } }
+
+##
+# @ChardevSocketWrapper:
+#
+# Since: 6.1
+##
+{ 'struct': 'ChardevSocketWrapper',
+  'data': { 'data': 'ChardevSocket' } }
+
+##
+# @ChardevUdpWrapper:
+#
+# Since: 6.1
+##
+{ 'struct': 'ChardevUdpWrapper',
+  'data': { 'data': 'ChardevUdp' } }
+
+##
+# @ChardevCommonWrapper:
+#
+# Since: 6.1
+##
+{ 'struct': 'ChardevCommonWrapper',
+  'data': { 'data': 'ChardevCommon' } }
+
+##
+# @ChardevMuxWrapper:
+#
+# Since: 6.1
+##
+{ 'struct': 'ChardevMuxWrapper',
+  'data': { 'data': 'ChardevMux' } }
+
+##
+# @ChardevStdioWrapper:
+#
+# Since: 6.1
+##
+{ 'struct': 'ChardevStdioWrapper',
+  'data': { 'data': 'ChardevStdio' } }
+
+##
+# @ChardevSpiceChannelWrapper:
+#
+# Since: 6.1
+##
+{ 'struct': 'ChardevSpiceChannelWrapper',
+  'data': { 'data': 'ChardevSpiceChannel' } }
+
+##
+# @ChardevSpicePortWrapper:
+#
+# Since: 6.1
+##
+{ 'struct': 'ChardevSpicePortWrapper',
+  'data': { 'data': 'ChardevSpicePort' } }
+
+##
+# @ChardevQemuVDAgentWrapper:
+#
+# Since: 6.1
+##
+{ 'struct': 'ChardevQemuVDAgentWrapper',
+  'data': { 'data': 'ChardevQemuVDAgent' } }
+
+##
+# @ChardevVCWrapper:
+#
+# Since: 6.1
+##
+{ 'struct': 'ChardevVCWrapper',
+  'data': { 'data': 'ChardevVC' } }
+
+##
+# @ChardevRingbufWrapper:
+#
+# Since: 6.1
+##
+{ 'struct': 'ChardevRingbufWrapper',
+  'data': { 'data': 'ChardevRingbuf' } }
+
 ##
 # @ChardevBackend:
 #
@@ -415,31 +540,33 @@
 # Since: 1.4 (testdev since 2.2, wctablet since 2.9, vdagent since 6.1)
 ##
 { 'union': 'ChardevBackend',
-  'data': { 'file': 'ChardevFile',
-            'serial': 'ChardevHostdev',
-            'parallel': 'ChardevHostdev',
-            'pipe': 'ChardevHostdev',
-            'socket': 'ChardevSocket',
-            'udp': 'ChardevUdp',
-            'pty': 'ChardevCommon',
-            'null': 'ChardevCommon',
-            'mux': 'ChardevMux',
-            'msmouse': 'ChardevCommon',
-            'wctablet': 'ChardevCommon',
-            'braille': 'ChardevCommon',
-            'testdev': 'ChardevCommon',
-            'stdio': 'ChardevStdio',
-            'console': 'ChardevCommon',
-            'spicevmc': { 'type': 'ChardevSpiceChannel',
+  'base': { 'type': 'ChardevBackendKind' },
+  'discriminator': 'type',
+  'data': { 'file': 'ChardevFileWrapper',
+            'serial': 'ChardevHostdevWrapper',
+            'parallel': 'ChardevHostdevWrapper',
+            'pipe': 'ChardevHostdevWrapper',
+            'socket': 'ChardevSocketWrapper',
+            'udp': 'ChardevUdpWrapper',
+            'pty': 'ChardevCommonWrapper',
+            'null': 'ChardevCommonWrapper',
+            'mux': 'ChardevMuxWrapper',
+            'msmouse': 'ChardevCommonWrapper',
+            'wctablet': 'ChardevCommonWrapper',
+            'braille': 'ChardevCommonWrapper',
+            'testdev': 'ChardevCommonWrapper',
+            'stdio': 'ChardevStdioWrapper',
+            'console': 'ChardevCommonWrapper',
+            'spicevmc': { 'type': 'ChardevSpiceChannelWrapper',
                           'if': 'CONFIG_SPICE' },
-            'spiceport': { 'type': 'ChardevSpicePort',
+            'spiceport': { 'type': 'ChardevSpicePortWrapper',
                            'if': 'CONFIG_SPICE' },
-            'qemu-vdagent': { 'type': 'ChardevQemuVDAgent',
+            'qemu-vdagent': { 'type': 'ChardevQemuVDAgentWrapper',
                               'if': 'CONFIG_SPICE_PROTOCOL' },
-            'vc': 'ChardevVC',
-            'ringbuf': 'ChardevRingbuf',
+            'vc': 'ChardevVCWrapper',
+            'ringbuf': 'ChardevRingbufWrapper',
             # next one is just for compatibility
-            'memory': 'ChardevRingbuf' } }
+            'memory': 'ChardevRingbufWrapper' } }
 
 ##
 # @ChardevReturn:
-- 
2.31.1