ueventd: require opt-in for modalias handling

Some devices have modules.alias and modules.dep for modprobe and other
purposes but do not want to opt into ueventd auto loading their
modules.  Therefore we add a flag that can be added to ueventd
configuration files to opt into this behavior.

Bug: 111916071
Bug: 112048758
Test: check that modules are loaded with this opt-in
Test: check that modules are not loaded without this opt-in
Change-Id: Ifb281b273059b4671eea1ca5bc726c9e79f3adfb
diff --git a/init/uevent_handler.h b/init/uevent_handler.h
new file mode 100644
index 0000000..75d1990
--- /dev/null
+++ b/init/uevent_handler.h
@@ -0,0 +1,34 @@
+/*
+ * Copyright (C) 2018 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#pragma once
+
+#include "uevent.h"
+
+namespace android {
+namespace init {
+
+class UeventHandler {
+  public:
+    virtual ~UeventHandler() = default;
+
+    virtual void HandleUevent(const Uevent& uevent) = 0;
+
+    virtual void ColdbootDone() {}
+};
+
+}  // namespace init
+}  // namespace android