libaudiohal: Implement simple HIDL client

This client requires both HIDL client and server to be of the same
ABI version (e.g. 32-bit).

EffectHalHidl::process and EffectHalHidl::processReverse are stubs.

Some extra warnings are logged due to unimplemented functions
in the legacy HAL.

Bug: 30222631
Change-Id: Id074131dec6d6c4f1031695abcf3ea066e92a5af
Test: Play Music (play / EQ), YouTube, Loopback RTLT, Ok Google on N5X
diff --git a/media/libaudiohal/DevicesFactoryHalHidl.h b/media/libaudiohal/DevicesFactoryHalHidl.h
new file mode 100644
index 0000000..a26dec1
--- /dev/null
+++ b/media/libaudiohal/DevicesFactoryHalHidl.h
@@ -0,0 +1,53 @@
+/*
+ * Copyright (C) 2016 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.
+ */
+
+#ifndef ANDROID_HARDWARE_DEVICES_FACTORY_HAL_HIDL_H
+#define ANDROID_HARDWARE_DEVICES_FACTORY_HAL_HIDL_H
+
+#include <android/hardware/audio/2.0/IDevicesFactory.h>
+#include <media/audiohal/DevicesFactoryHalInterface.h>
+#include <utils/Errors.h>
+#include <utils/RefBase.h>
+
+#include "DeviceHalHidl.h"
+
+using ::android::hardware::audio::V2_0::IDevicesFactory;
+
+namespace android {
+
+class DevicesFactoryHalHidl : public DevicesFactoryHalInterface
+{
+  public:
+    // Opens a device with the specified name. To close the device, it is
+    // necessary to release references to the returned object.
+    virtual status_t openDevice(const char *name, sp<DeviceHalInterface> *device);
+
+  private:
+    friend class DevicesFactoryHalInterface;
+
+    sp<IDevicesFactory> mDevicesFactory;
+
+    static status_t nameFromHal(const char *name, IDevicesFactory::Device *device);
+
+    // Can not be constructed directly by clients.
+    DevicesFactoryHalHidl();
+
+    virtual ~DevicesFactoryHalHidl();
+};
+
+} // namespace android
+
+#endif // ANDROID_HARDWARE_DEVICES_FACTORY_HAL_HIDL_H