[RFC PATCH-for-9.0 01/11] qom: Introduce the TypeInfo::can_register() handler

["Philippe Mathieu-Daudé" <philmd@linaro.org>]

Add a helper to decide at runtime whether a type can
be registered to the QOM framework or not.

Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
---
 include/qom/object.h | 4 ++++
 qom/object.c         | 3 +++
 2 files changed, 7 insertions(+)

diff --git a/include/qom/object.h b/include/qom/object.h
index afccd24ca7..0d42fe17de 100644
--- a/include/qom/object.h
+++ b/include/qom/object.h
@@ -372,6 +372,8 @@ struct Object
  * struct TypeInfo:
  * @name: The name of the type.
  * @parent: The name of the parent type.
+ * @can_register: This optional function is called before a type is registered.
+ *   If it exists and returns false, the type is not registered.
  * @instance_size: The size of the object (derivative of #Object).  If
  *   @instance_size is 0, then the size of the object will be the size of the
  *   parent object.
@@ -414,6 +416,8 @@ struct TypeInfo
     const char *name;
     const char *parent;
 
+    bool (*can_register)(void);
+
     size_t instance_size;
     size_t instance_align;
     void (*instance_init)(Object *obj);
diff --git a/qom/object.c b/qom/object.c
index 95c0dc8285..f09b6b5a92 100644
--- a/qom/object.c
+++ b/qom/object.c
@@ -150,6 +150,9 @@ static TypeImpl *type_register_internal(const TypeInfo *info)
 TypeImpl *type_register(const TypeInfo *info)
 {
     assert(info->parent);
+    if (info->can_register && !info->can_register()) {
+        return NULL;
+    }
     return type_register_internal(info);
 }
 
-- 
2.41.0