audio: Add example HAL implementation

This is partial implementation of the example V7.0 audio HAL
which passes VTS tests. Note that the 'core' part
of the HAL (IDevice/IStream) isn't implemented yet.
It passes VTS because it doesn't provide any devices
(modules) and the audio HAL isn't the 'default' instance.

Bug: 142480271
Test: atest VtsHalAudioV7_0TargetTest
      atest VtsHalAudioEffectV7_0TargetTest
Change-Id: Ie3dd62c5db1cdb5534df4dd7f326c4c8776bf3c4
diff --git a/audio/common/7.0/example/DevicesFactory.h b/audio/common/7.0/example/DevicesFactory.h
new file mode 100644
index 0000000..00f665c
--- /dev/null
+++ b/audio/common/7.0/example/DevicesFactory.h
@@ -0,0 +1,33 @@
+/*
+ * Copyright (C) 2020 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 <android/hardware/audio/7.0/IDevicesFactory.h>
+
+namespace android::hardware::audio::V7_0::implementation {
+
+class DevicesFactory : public IDevicesFactory {
+  public:
+    DevicesFactory() = default;
+
+    ::android::hardware::Return<void> openDevice(const ::android::hardware::hidl_string& device,
+                                                 openDevice_cb _hidl_cb) override;
+
+    ::android::hardware::Return<void> openPrimaryDevice(openPrimaryDevice_cb _hidl_cb) override;
+};
+
+}  // namespace android::hardware::audio::V7_0::implementation