[PATCH 01/14] qom/object: add is_available callback to TypeInfo

[Pierrick Bouvier <pierrick.bouvier@oss.qualcomm.com>]

When removing target specific sections (#ifdef TARGET_X), we started
exposing types for different targets in the same file.

Previously, we implemented a filter based on interfaces, but it
proved to be too cumbersome, requiring duplication across architectures.
To simplify it, we add a new callback, is_available, to TypeInfo, that
will replace the existing filtering mechanism.

Signed-off-by: Pierrick Bouvier <pierrick.bouvier@oss.qualcomm.com>
---
 include/qom/object.h | 3 +++
 qom/object.c         | 4 ++++
 rust/qom/src/qom.rs  | 1 +
 3 files changed, 8 insertions(+)

diff --git a/include/qom/object.h b/include/qom/object.h
index e24f0a2b2d0..7ecd0f210fb 100644
--- a/include/qom/object.h
+++ b/include/qom/object.h
@@ -469,6 +469,8 @@ struct Object
  * @class_data: Data to pass to the @class_init,
  *   @class_base_init. This can be useful when building dynamic
  *   classes.
+ * @is_available: callback invoked at registration time, to dynamically check if
+ *   this type should be available or not.
  * @interfaces: The list of interfaces associated with this type.  This
  *   should point to a static array that's terminated with a zero filled
  *   element.
@@ -491,6 +493,7 @@ struct TypeInfo
     void (*class_base_init)(ObjectClass *klass, const void *data);
     const void *class_data;
 
+    bool (*is_available)(void);
     const InterfaceInfo *interfaces;
 };
 
diff --git a/qom/object.c b/qom/object.c
index 85bbd7f9fe1..b1834a57cc9 100644
--- a/qom/object.c
+++ b/qom/object.c
@@ -163,6 +163,10 @@ static TypeImpl *type_register_internal(const TypeInfo *info)
         abort();
     }
 
+    if (info->is_available && !info->is_available()) {
+        return NULL;
+    }
+
     ti = type_new(info);
 
     type_table_add(ti);
diff --git a/rust/qom/src/qom.rs b/rust/qom/src/qom.rs
index cc00ddcfc98..bbb485e2cfd 100644
--- a/rust/qom/src/qom.rs
+++ b/rust/qom/src/qom.rs
@@ -691,6 +691,7 @@ pub trait ObjectImpl: ObjectType + IsA<Object> {
         class_init: Some(rust_class_init::<Self>),
         class_base_init: Self::CLASS_BASE_INIT,
         class_data: core::ptr::null(),
+        is_available: None,
         interfaces: core::ptr::null(),
     };
 
-- 
2.43.0