[core] Remove indirection from ControllerRegistry dispatch (#15173)

esphome/core/controller_registry.cpp

@@ -10,24 +10,24 @@ StaticVector<Controller *, CONTROLLER_REGISTRY_MAX> ControllerRegistry::controll
 
 void ControllerRegistry::register_controller(Controller *controller) { controllers.push_back(controller); }
 
-void ControllerRegistry::notify(void *obj, DispatchFunc dispatch) {
-  for (auto *controller : controllers) {
-    dispatch(controller, obj);
-  }
-}
-
-// Macro for standard registry notification dispatch - calls on_<entity_name>_update()
-// Each wrapper passes a small trampoline lambda that calls the correct virtual method.
+// Each notify method directly iterates controllers and calls the virtual method.
+// This avoids the overhead of a shared noinline dispatch loop with function pointer
+// indirection. The loop is tiny (~20 bytes per entity type) so the flash cost of
+// duplicating it is negligible compared to eliminating two levels of indirection
+// (noinline call + function pointer) from every state publish.
 // NOLINTBEGIN(bugprone-macro-parentheses)
 #define CONTROLLER_REGISTRY_NOTIFY(entity_type, entity_name) \
   void ControllerRegistry::notify_##entity_name##_update(entity_type *obj) { \
-    notify(obj, [](Controller *c, void *o) { c->on_##entity_name##_update(static_cast<entity_type *>(o)); }); \
+    for (auto *controller : controllers) { \
+      controller->on_##entity_name##_update(obj); \
+    } \
   }
 
-// Macro for entities where controller method has no "_update" suffix (Event, Update)
 #define CONTROLLER_REGISTRY_NOTIFY_NO_UPDATE_SUFFIX(entity_type, entity_name) \
   void ControllerRegistry::notify_##entity_name(entity_type *obj) { \
-    notify(obj, [](Controller *c, void *o) { c->on_##entity_name(static_cast<entity_type *>(o)); }); \
+    for (auto *controller : controllers) { \
+      controller->on_##entity_name(obj); \
+    } \
   }
 // NOLINTEND(bugprone-macro-parentheses)
 

esphome/core/controller_registry.h

@@ -146,8 +146,8 @@ class UpdateEntity;
  * entities call ControllerRegistry::notify_*_update() which iterates the small list
  * of registered controllers (typically 2: API and WebServer).
  *
- * Controllers read state directly from entities using existing accessors (obj->state, etc.)
- * rather than receiving it as callback parameters that were being ignored anyway.
+ * Each notify method directly iterates controllers and calls the virtual method,
+ * avoiding function pointer indirection for minimal dispatch overhead.
  *
  * Memory savings: 32 bytes per entity (2 controllers × 16 bytes std::function overhead)
  * Typical config (25 entities): ~780 bytes saved
@@ -247,21 +247,6 @@ class ControllerRegistry {
 #endif
 
  protected:
-  /** Type-erased dispatch function pointer.
-   *
-   * Each notify method passes a small trampoline that calls the
-   * correct virtual method on Controller. The shared notify() loop
-   * iterates controllers once, calling the trampoline for each.
-   */
-  using DispatchFunc = void (*)(Controller *, void *);
-
-  /** Shared dispatch loop - iterates controllers and calls dispatch for each.
-   *
-   * Marked noinline to ensure only one copy of the loop exists in flash,
-   * rather than being duplicated into each notify_*_update wrapper.
-   */
-  static void __attribute__((noinline)) notify(void *obj, DispatchFunc dispatch);
-
   static StaticVector<Controller *, CONTROLLER_REGISTRY_MAX> controllers;
 };