Add a way to unregister AttributeAccessInterface instances. (#28075)

Fixes #28072
project-chip · Nov 7, 2023 · 1156840 · 1156840
1 parent dae7c4b
commit 1156840
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Showing 2 changed files with 55 additions and 33 deletions.
diff --git a/src/app/util/attribute-storage.cpp b/src/app/util/attribute-storage.cpp
@@ -118,7 +118,42 @@ DataVersion fixedEndpointDataVersions[ZAP_FIXED_ENDPOINT_DATA_VERSION_COUNT];
 #define endpointTypeMacro(x) (&(generatedEmberAfEndpointTypes[fixedEmberAfEndpointTypes[x]]))
 #endif
 
-app::AttributeAccessInterface * gAttributeAccessOverrides = nullptr;
+AttributeAccessInterface * gAttributeAccessOverrides = nullptr;
+
+// shouldUnregister returns true if the given AttributeAccessInterface should be
+// unregistered.
+template <typename F>
+void UnregisterMatchingAttributeAccessInterfaces(F shouldUnregister)
+{
+    AttributeAccessInterface * prev = nullptr;
+    AttributeAccessInterface * cur  = gAttributeAccessOverrides;
+    while (cur)
+    {
+        AttributeAccessInterface * next = cur->GetNext();
+        if (shouldUnregister(cur))
+        {
+            // Remove it from the list
+            if (prev)
+            {
+                prev->SetNext(next);
+            }
+            else
+            {
+                gAttributeAccessOverrides = next;
+            }
+
+            cur->SetNext(nullptr);
+
+            // Do not change prev in this case.
+        }
+        else
+        {
+            prev = cur;
+        }
+        cur = next;
+    }
+}
+
 } // anonymous namespace
 
 // Initial configuration
@@ -383,33 +418,8 @@ static void shutdownEndpoint(EmberAfDefinedEndpoint * definedEndpoint)
 
     // Clear out any attribute access overrides registered for this
     // endpoint.
-    app::AttributeAccessInterface * prev = nullptr;
-    app::AttributeAccessInterface * cur  = gAttributeAccessOverrides;
-    while (cur)
-    {
-        app::AttributeAccessInterface * next = cur->GetNext();
-        if (cur->MatchesEndpoint(definedEndpoint->endpoint))
-        {
-            // Remove it from the list
-            if (prev)
-            {
-                prev->SetNext(next);
-            }
-            else
-            {
-                gAttributeAccessOverrides = next;
-            }
-
-            cur->SetNext(nullptr);
-
-            // Do not change prev in this case.
-        }
-        else
-        {
-            prev = cur;
-        }
-        cur = next;
-    }
+    UnregisterMatchingAttributeAccessInterfaces(
+        [endpoint = definedEndpoint->endpoint](AttributeAccessInterface * entry) { return entry->MatchesEndpoint(endpoint); });
 }
 
 // Calls the init functions.
@@ -1378,7 +1388,7 @@ EmberAfGenericClusterFunction emberAfFindClusterFunction(const EmberAfCluster *
     return cluster->functions[functionIndex];
 }
 
-bool registerAttributeAccessOverride(app::AttributeAccessInterface * attrOverride)
+bool registerAttributeAccessOverride(AttributeAccessInterface * attrOverride)
 {
     for (auto * cur = gAttributeAccessOverrides; cur; cur = cur->GetNext())
     {
@@ -1393,6 +1403,11 @@ bool registerAttributeAccessOverride(app::AttributeAccessInterface * attrOverrid
     return true;
 }
 
+void unregisterAttributeAccessOverride(AttributeAccessInterface * attrOverride)
+{
+    UnregisterMatchingAttributeAccessInterfaces([attrOverride](AttributeAccessInterface * entry) { return entry == attrOverride; });
+}
+
 namespace chip {
 namespace app {
 app::AttributeAccessInterface * GetAttributeAccessOverride(EndpointId endpointId, ClusterId clusterId)

diff --git a/src/app/util/attribute-storage.h b/src/app/util/attribute-storage.h
@@ -248,13 +248,20 @@ chip::Optional<chip::AttributeId> emberAfGetServerAttributeIdByIndex(chip::Endpo
                                                                      uint16_t attributeIndex);
 
 /**
- * Register an attribute access override.  It will remain registered until
- * the endpoint it's registered for is disabled (or until shutdown if it's
- * registered for all endpoints).  Registration will fail if there is an
- * already-registered override for the same set of attributes.
+ * Register an attribute access override.  It will remain registered until the
+ * endpoint it's registered for is disabled (or until shutdown if it's
+ * registered for all endpoints) or until it is explicitly unregistered.
+ * Registration will fail if there is an already-registered override for the
+ * same set of attributes.
  *
  * @return false if there is an existing override that the new one would
  *               conflict with.  In this case the override is not registered.
  * @return true if registration was successful.
  */
 bool registerAttributeAccessOverride(chip::app::AttributeAccessInterface * attrOverride);
+
+/**
+ * Unregister an attribute access override (for example if the object
+ * implementing AttributeAccessInterface is being destroyed).
+ */
+void unregisterAttributeAccessOverride(chip::app::AttributeAccessInterface * attrOverride);