[Qemu-devel] [PATCH 1/2] qapi: Add feature flags to commands in qapi introspection

[Peter Krempa]

Similarly to features for struct types introduce the feature flags also
for commands. This will allow notifying management layers of fixes and
compatible changes in the behaviour of an command which may not be
detectable any other way.

The changes were heavily inspired by commit 6a8c0b51025.

Signed-off-by: Peter Krempa <address@hidden>
---
 docs/devel/qapi-code-gen.txt   |  4 ++--
 qapi/introspect.json           |  6 ++++-
 scripts/qapi/commands.py       |  3 ++-
 scripts/qapi/common.py         | 40 +++++++++++++++++++++++++++++-----
 scripts/qapi/doc.py            |  3 ++-
 scripts/qapi/introspect.py     |  7 +++++-
 tests/qapi-schema/test-qapi.py |  7 +++++-
 7 files changed, 58 insertions(+), 12 deletions(-)

diff --git a/docs/devel/qapi-code-gen.txt b/docs/devel/qapi-code-gen.txt
index e8ec8ac1de..38682daace 100644
--- a/docs/devel/qapi-code-gen.txt
+++ b/docs/devel/qapi-code-gen.txt
@@ -726,8 +726,8 @@ change in the QMP syntax (usually by allowing values or 
operations that
 previously resulted in an error). QMP clients may still need to know
 whether the extension is available.

-For this purpose, a list of features can be specified for a struct type.
-This is exposed to the client as a list of string, where each string
+For this purpose, a list of features can be specified for a command or struct
+type. This is exposed to the client as a list of string, where each string
 signals that this build of QEMU shows a certain behaviour.

 In the schema, features can be specified as simple strings, for example:
diff --git a/qapi/introspect.json b/qapi/introspect.json
index 1843c1cb17..031a954fa9 100644
--- a/qapi/introspect.json
+++ b/qapi/introspect.json
@@ -266,13 +266,17 @@
 # @allow-oob: whether the command allows out-of-band execution,
 #             defaults to false (Since: 2.12)
 #
+# @features: names of features associated with the command, in no particular
+#            order. (since 4.2)
+#
 # TODO: @success-response (currently irrelevant, because it's QGA, not QMP)
 #
 # Since: 2.5
 ##
 { 'struct': 'SchemaInfoCommand',
   'data': { 'arg-type': 'str', 'ret-type': 'str',
-            '*allow-oob': 'bool' } }
+            '*allow-oob': 'bool',
+            '*features': [ 'str' ] } }

 ##
 # @SchemaInfoEvent:
diff --git a/scripts/qapi/commands.py b/scripts/qapi/commands.py
index b929e07be4..6cfe6cdd9e 100644
--- a/scripts/qapi/commands.py
+++ b/scripts/qapi/commands.py
@@ -276,7 +276,8 @@ void %(c_prefix)sqmp_init_marshal(QmpCommandList *cmds);
         genc.add(gen_registry(self._regy.get_content(), self._prefix))

     def visit_command(self, name, info, ifcond, arg_type, ret_type, gen,
-                      success_response, boxed, allow_oob, allow_preconfig):
+                      success_response, boxed, allow_oob, allow_preconfig,
+                      features):
         if not gen:
             return
         # FIXME: If T is a user-defined type, the user is responsible
diff --git a/scripts/qapi/common.py b/scripts/qapi/common.py
index d61bfdc526..1502820f46 100644
--- a/scripts/qapi/common.py
+++ b/scripts/qapi/common.py
@@ -838,6 +838,7 @@ def check_type(info, source, value, allow_array=False,
 def check_command(expr, info):
     name = expr['command']
     boxed = expr.get('boxed', False)
+    features = expr.get('features')

     args_meta = ['struct']
     if boxed:
@@ -852,6 +853,19 @@ def check_command(expr, info):
                expr.get('returns'), allow_array=True,
                allow_optional=True, allow_metas=returns_meta)

+    if features:
+        if not isinstance(features, list):
+            raise QAPISemError(info,
+                               "Command '%s' requires an array for 'features'" 
%
+                               name)
+        for f in features:
+            assert isinstance(f, dict)
+            check_known_keys(info, "feature of command %s" % name, f,
+                             ['name'], ['if'])
+
+            check_if(f, info)
+            check_name(info, "Feature of command %s" % name, f['name'])
+

 def check_event(expr, info):
     name = expr['event']
@@ -1138,8 +1152,10 @@ def check_exprs(exprs):
             meta = 'command'
             check_keys(expr_elem, 'command', [],
                        ['data', 'returns', 'gen', 'success-response',
-                        'boxed', 'allow-oob', 'allow-preconfig', 'if'])
+                        'boxed', 'allow-oob', 'allow-preconfig', 'if',
+                        'features'])
             normalize_members(expr.get('data'))
+            normalize_features(expr.get('features'))
         elif 'event' in expr:
             meta = 'event'
             check_keys(expr_elem, 'event', [], ['data', 'boxed', 'if'])
@@ -1283,7 +1299,8 @@ class QAPISchemaVisitor(object):
         pass

     def visit_command(self, name, info, ifcond, arg_type, ret_type, gen,
-                      success_response, boxed, allow_oob, allow_preconfig):
+                      success_response, boxed, allow_oob, allow_preconfig,
+                      features):
         pass

     def visit_event(self, name, info, ifcond, arg_type, boxed):
@@ -1697,10 +1714,14 @@ class QAPISchemaAlternateType(QAPISchemaType):

 class QAPISchemaCommand(QAPISchemaEntity):
     def __init__(self, name, info, doc, ifcond, arg_type, ret_type,
-                 gen, success_response, boxed, allow_oob, allow_preconfig):
+                 gen, success_response, boxed, allow_oob, allow_preconfig,
+                 features):
         QAPISchemaEntity.__init__(self, name, info, doc, ifcond)
         assert not arg_type or isinstance(arg_type, str)
         assert not ret_type or isinstance(ret_type, str)
+        for f in features:
+            assert isinstance(f, QAPISchemaFeature)
+            f.set_owner(name)
         self._arg_type_name = arg_type
         self.arg_type = None
         self._ret_type_name = ret_type
@@ -1710,6 +1731,7 @@ class QAPISchemaCommand(QAPISchemaEntity):
         self.boxed = boxed
         self.allow_oob = allow_oob
         self.allow_preconfig = allow_preconfig
+        self.features = features

     def check(self, schema):
         QAPISchemaEntity.check(self, schema)
@@ -1731,12 +1753,18 @@ class QAPISchemaCommand(QAPISchemaEntity):
             self.ret_type = schema.lookup_type(self._ret_type_name)
             assert isinstance(self.ret_type, QAPISchemaType)

+        # Features are in a name space separate from members
+        seen = {}
+        for f in self.features:
+            f.check_clash(self.info, seen)
+
     def visit(self, visitor):
         visitor.visit_command(self.name, self.info, self.ifcond,
                               self.arg_type, self.ret_type,
                               self.gen, self.success_response,
                               self.boxed, self.allow_oob,
-                              self.allow_preconfig)
+                              self.allow_preconfig,
+                              self.features)


 class QAPISchemaEvent(QAPISchemaEntity):
@@ -1989,6 +2017,7 @@ class QAPISchema(object):
         allow_oob = expr.get('allow-oob', False)
         allow_preconfig = expr.get('allow-preconfig', False)
         ifcond = expr.get('if')
+        features = expr.get('features', [])
         if isinstance(data, OrderedDict):
             data = self._make_implicit_object_type(
                 name, info, doc, ifcond, 'arg', self._make_members(data, info))
@@ -1997,7 +2026,8 @@ class QAPISchema(object):
             rets = self._make_array_type(rets[0], info)
         self._def_entity(QAPISchemaCommand(name, info, doc, ifcond, data, rets,
                                            gen, success_response,
-                                           boxed, allow_oob, allow_preconfig))
+                                           boxed, allow_oob, allow_preconfig,
+                                           self._make_features(features)))

     def _def_event(self, expr, info, doc):
         name = expr['event']
diff --git a/scripts/qapi/doc.py b/scripts/qapi/doc.py
index 5fc0fc7e06..aa4c557244 100755
--- a/scripts/qapi/doc.py
+++ b/scripts/qapi/doc.py
@@ -249,7 +249,8 @@ class 
QAPISchemaGenDocVisitor(qapi.common.QAPISchemaVisitor):
                                body=texi_entity(doc, 'Members', ifcond)))

     def visit_command(self, name, info, ifcond, arg_type, ret_type, gen,
-                      success_response, boxed, allow_oob, allow_preconfig):
+                      success_response, boxed, allow_oob, allow_preconfig,
+                      features):
         doc = self.cur_doc
         if boxed:
             body = texi_body(doc)
diff --git a/scripts/qapi/introspect.py b/scripts/qapi/introspect.py
index f62cf0a2e1..36a5b195e5 100644
--- a/scripts/qapi/introspect.py
+++ b/scripts/qapi/introspect.py
@@ -206,13 +206,18 @@ const QLitObject %(c_name)s = %(c_string)s;
                            for m in variants.variants]}, ifcond)

     def visit_command(self, name, info, ifcond, arg_type, ret_type, gen,
-                      success_response, boxed, allow_oob, allow_preconfig):
+                      success_response, boxed, allow_oob, allow_preconfig,
+                      features):
         arg_type = arg_type or self._schema.the_empty_object_type
         ret_type = ret_type or self._schema.the_empty_object_type
         obj = {'arg-type': self._use_type(arg_type),
                'ret-type': self._use_type(ret_type)}
         if allow_oob:
             obj['allow-oob'] = allow_oob
+
+        if features:
+            obj['features'] = [(f.name, {'if': f.ifcond}) for f in features]
+
         self._gen_qlit(name, 'command', obj, ifcond)

     def visit_event(self, name, info, ifcond, arg_type, boxed):
diff --git a/tests/qapi-schema/test-qapi.py b/tests/qapi-schema/test-qapi.py
index b0f770b9bd..def34aa489 100644
--- a/tests/qapi-schema/test-qapi.py
+++ b/tests/qapi-schema/test-qapi.py
@@ -60,13 +60,18 @@ class QAPISchemaTestVisitor(QAPISchemaVisitor):
         self._print_if(ifcond)

     def visit_command(self, name, info, ifcond, arg_type, ret_type, gen,
-                      success_response, boxed, allow_oob, allow_preconfig):
+                      success_response, boxed, allow_oob, allow_preconfig,
+                      features):
         print('command %s %s -> %s'
               % (name, arg_type and arg_type.name,
                  ret_type and ret_type.name))
         print('   gen=%s success_response=%s boxed=%s oob=%s preconfig=%s'
               % (gen, success_response, boxed, allow_oob, allow_preconfig))
         self._print_if(ifcond)
+        if features:
+            for f in features:
+                print('    feature %s' % f.name)
+                self._print_if(f.ifcond, 8)

     def visit_event(self, name, info, ifcond, arg_type, boxed):
         print('event %s %s' % (name, arg_type and arg_type.name))
-- 
2.21.0