Added comment for behavior in case of changes in kMaxScenePerFabric a…

…nd kMaxClustersPerScene

src/app/clusters/scenes/ExtensionFieldSetsImpl.cpp

@@ -57,6 +57,10 @@ CHIP_ERROR ExtensionFieldSetsImpl::Deserialize(TLV::TLVReader & reader, TLV::Tag
     }
     mFieldSetsCount = i;
 
+    // In the event of an OTA where the maximum number of cluster per scene has been reduced, the extension field set will be
+    // considered "corrupted" if we don't manage to load it all (if err == CHIP_NO_ERROR after the loop). We therefore return an
+    // error and this scene will have to be deleted. This is done because truncating an EFS doesn't garrantee the order of the
+    // clusters loaded, which might allow to load clusters that are no longer supported and loosing supported ones.
     if (err != CHIP_END_OF_TLV)
     {
         if (err == CHIP_NO_ERROR)

src/app/clusters/scenes/SceneTableImpl.cpp

@@ -226,6 +226,9 @@ struct FabricSceneData : public PersistentData<kPersistentFabricBufferMax>
 
             i++;
         }
+        // In the event of an OTA, is kMaxScenesPerFabric was reduced, err will be equal to CHIP_NO_ERROR. We close the TLV with
+        // only the acceptable number of scenes and the next save will take care of reducing the memory usage of the map. This
+        // allows the user to preserve their scenes in between OTA updates.
         VerifyOrReturnError(err == CHIP_END_OF_TLV || err == CHIP_NO_ERROR, err);
 
         ReturnErrorOnFailure(reader.ExitContainer(sceneMapContainer));

src/app/tests/TestSceneTable.cpp

@@ -435,7 +435,6 @@ void TestHandlerRegistration(nlTestSuite * aSuite, void * aContext)
 void TestHandlerFunctions(nlTestSuite * aSuite, void * aContext)
 {
     SceneTable * sceneTable = &sSceneTable;
-    ClusterId tempCluster   = 0;
 
     app::Clusters::Scenes::Structs::ExtensionFieldSet::Type extensionFieldSetOut;
     app::Clusters::Scenes::Structs::ExtensionFieldSet::DecodableType extensionFieldSetIn;