[PATCH v2 4/4] qapi: expose all schema features to code

["Daniel P. Berrangé" <berrange@redhat.com>]

This replaces use of the constants from the QapiSpecialFeatures
enum, with constants from the auto-generate QapiFeatures enum
in qapi-features.h

The 'deprecated' and 'unstable' features still have a little bit of
special handling, being force defined to be the 1st + 2nd features
in the enum, regardless of whether they're used in the schema. This
retains compatibility with common code that references the features
via the QapiSpecialFeatures constants.

Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
---
 meson.build              |  1 +
 scripts/qapi/commands.py |  1 +
 scripts/qapi/features.py | 62 ++++++++++++++++++++++++++++++++++++++++
 scripts/qapi/gen.py      |  4 +--
 scripts/qapi/main.py     |  2 ++
 scripts/qapi/schema.py   | 19 +++++++++++-
 scripts/qapi/types.py    |  6 ++--
 scripts/qapi/visit.py    |  3 +-
 8 files changed, 92 insertions(+), 6 deletions(-)
 create mode 100644 scripts/qapi/features.py

diff --git a/meson.build b/meson.build
index d26690ce20..b9d58be66f 100644
--- a/meson.build
+++ b/meson.build
@@ -3332,6 +3332,7 @@ qapi_gen_depends = [ meson.current_source_dir() / 'scripts/qapi/__init__.py',
                      meson.current_source_dir() / 'scripts/qapi/schema.py',
                      meson.current_source_dir() / 'scripts/qapi/source.py',
                      meson.current_source_dir() / 'scripts/qapi/types.py',
+                     meson.current_source_dir() / 'scripts/qapi/features.py',
                      meson.current_source_dir() / 'scripts/qapi/visit.py',
                      meson.current_source_dir() / 'scripts/qapi-gen.py'
 ]
diff --git a/scripts/qapi/commands.py b/scripts/qapi/commands.py
index d629d2d97e..bf88bfc442 100644
--- a/scripts/qapi/commands.py
+++ b/scripts/qapi/commands.py
@@ -355,6 +355,7 @@ def visit_begin(self, schema: QAPISchema) -> None:
 #include "qemu/osdep.h"
 #include "%(prefix)sqapi-commands.h"
 #include "%(prefix)sqapi-init-commands.h"
+#include "%(prefix)sqapi-features.h"
 
 void %(c_prefix)sqmp_init_marshal(QmpCommandList *cmds)
 {
diff --git a/scripts/qapi/features.py b/scripts/qapi/features.py
new file mode 100644
index 0000000000..dc10c7cea0
--- /dev/null
+++ b/scripts/qapi/features.py
@@ -0,0 +1,62 @@
+"""
+QAPI types generator
+
+Copyright 2024 Red Hat
+
+This work is licensed under the terms of the GNU GPL, version 2.
+# See the COPYING file in the top-level directory.
+"""
+
+from typing import List, Optional
+
+from .common import c_enum_const, mcgen, c_name
+from .gen import QAPISchemaMonolithicCVisitor
+from .schema import (
+    QAPISchema,
+    QAPISchemaFeature,
+)
+from .source import QAPISourceInfo
+
+
+class QAPISchemaGenFeatureVisitor(QAPISchemaMonolithicCVisitor):
+
+    def __init__(self, prefix: str):
+        super().__init__(
+            prefix, 'qapi-features',
+            ' * Schema-defined QAPI features',
+            __doc__)
+
+        self.features = {}
+
+    def visit_begin(self, schema: QAPISchema):
+        self.features = schema._feature_dict
+
+    def visit_end(self) -> None:
+        features = [
+            self.features[f]
+            for f in QAPISchemaFeature.SPECIAL_NAMES
+        ]
+
+        features.extend(
+            sorted(
+                filter(lambda f: not f.is_special(),
+                       self.features.values()),
+                key=lambda f: f.name)
+        )
+
+        self._genh.add("typedef enum {\n")
+        for f in features:
+            self._genh.add(f"    {c_enum_const('qapi_feature', f.name)}")
+            if f.name in QAPISchemaFeature.SPECIAL_NAMES:
+                self._genh.add(f" = {c_enum_const('qapi', f.name)},\n" )
+            else:
+                self._genh.add(",\n")
+
+        self._genh.add("} " + c_name('QapiFeature') + ";\n")
+
+def gen_features(schema: QAPISchema,
+                 output_dir: str,
+                 prefix: str) -> None:
+    vis = QAPISchemaGenFeatureVisitor(prefix)
+    schema.visit(vis)
+    vis.write(output_dir)
diff --git a/scripts/qapi/gen.py b/scripts/qapi/gen.py
index aba1a982f6..6ef603941c 100644
--- a/scripts/qapi/gen.py
+++ b/scripts/qapi/gen.py
@@ -42,8 +42,8 @@
 
 
 def gen_features(features: Sequence[QAPISchemaFeature]) -> str:
-    features = [f"1u << {c_enum_const('qapi', feat.name)}"
-                        for feat in features if feat.is_special()]
+    features = [f"1u << {c_enum_const('qapi_feature', feat.name)}"
+                        for feat in features]
     return ' | '.join(features) or '0'
 
 
diff --git a/scripts/qapi/main.py b/scripts/qapi/main.py
index 316736b6a2..2b9a2c0c02 100644
--- a/scripts/qapi/main.py
+++ b/scripts/qapi/main.py
@@ -18,6 +18,7 @@
 from .introspect import gen_introspect
 from .schema import QAPISchema
 from .types import gen_types
+from .features import gen_features
 from .visit import gen_visit
 
 
@@ -49,6 +50,7 @@ def generate(schema_file: str,
 
     schema = QAPISchema(schema_file)
     gen_types(schema, output_dir, prefix, builtins)
+    gen_features(schema, output_dir, prefix)
     gen_visit(schema, output_dir, prefix, builtins)
     gen_commands(schema, output_dir, prefix, gen_tracing)
     gen_events(schema, output_dir, prefix)
diff --git a/scripts/qapi/schema.py b/scripts/qapi/schema.py
index e97c978d38..5e14b1829b 100644
--- a/scripts/qapi/schema.py
+++ b/scripts/qapi/schema.py
@@ -933,8 +933,11 @@ def connect_doc(self, doc: Optional[QAPIDoc]) -> None:
 class QAPISchemaFeature(QAPISchemaMember):
     role = 'feature'
 
+    # Features which are standardized across all schemas
+    SPECIAL_NAMES = ['deprecated', 'unstable']
+
     def is_special(self) -> bool:
-        return self.name in ('deprecated', 'unstable')
+        return self.name in QAPISchemaFeature.SPECIAL_NAMES
 
 
 class QAPISchemaObjectTypeMember(QAPISchemaMember):
@@ -1138,6 +1141,11 @@ def __init__(self, fname: str):
         self._entity_list: List[QAPISchemaEntity] = []
         self._entity_dict: Dict[str, QAPISchemaDefinition] = {}
         self._module_dict: Dict[str, QAPISchemaModule] = OrderedDict()
+        self._feature_dict: Dict[str, QAPISchemaFeature] = {}
+
+        for f in QAPISchemaFeature.SPECIAL_NAMES:
+            self._feature_dict[f] = QAPISchemaFeature(f, "special feature")
+
         self._schema_dir = os.path.dirname(fname)
         self._make_module(QAPISchemaModule.BUILTIN_MODULE_NAME)
         self._make_module(fname)
@@ -1258,6 +1266,15 @@ def _make_features(
     ) -> List[QAPISchemaFeature]:
         if features is None:
             return []
+
+        for f in features:
+            feat = QAPISchemaFeature(f['name'], info)
+            if feat.name not in self._feature_dict:
+                if len(self._feature_dict) == 64:
+                    raise Exception("Maximum of 64 schema features is permitted")
+
+                self._feature_dict[feat.name] = feat
+
         return [QAPISchemaFeature(f['name'], info,
                                   QAPISchemaIfCond(f.get('if')))
                 for f in features]
diff --git a/scripts/qapi/types.py b/scripts/qapi/types.py
index ade6b7a3d7..7618d3eb6f 100644
--- a/scripts/qapi/types.py
+++ b/scripts/qapi/types.py
@@ -308,11 +308,13 @@ def _begin_user_module(self, name: str) -> None:
 #include "qapi/dealloc-visitor.h"
 #include "%(types)s.h"
 #include "%(visit)s.h"
+#include "%(prefix)sqapi-features.h"
 ''',
-                                      types=types, visit=visit))
+                                      types=types, visit=visit, prefix=self._prefix))
         self._genh.preamble_add(mcgen('''
 #include "qapi/qapi-builtin-types.h"
-'''))
+''',
+                                      prefix=self._prefix))
 
     def visit_begin(self, schema: QAPISchema) -> None:
         # gen_object() is recursive, ensure it doesn't visit the empty type
diff --git a/scripts/qapi/visit.py b/scripts/qapi/visit.py
index 8dbf4ef1c3..2d678c281d 100644
--- a/scripts/qapi/visit.py
+++ b/scripts/qapi/visit.py
@@ -360,8 +360,9 @@ def _begin_user_module(self, name: str) -> None:
 #include "qemu/osdep.h"
 #include "qapi/error.h"
 #include "%(visit)s.h"
+#include "%(prefix)sqapi-features.h"
 ''',
-                                      visit=visit))
+                                      visit=visit, prefix=self._prefix))
         self._genh.preamble_add(mcgen('''
 #include "qapi/qapi-builtin-visit.h"
 #include "%(types)s.h"
-- 
2.46.0