drm_hwcomposer: Add hwc3 frontend stub

Adds a stub implementation of the HWC3 interface and service.
This is a barebones implementation of HWC3 interface that should contain
all the necessary code to build a HWC3 module but provides no
functionality.

The project [1] was used as a reference.
[1]: https://android.googlesource.com/platform/hardware/google/graphics/common/+/refs/tags/android-13.0.0_r18/hwc3/

Change-Id: I99754bb72f12183a94b24b7182cb7857173b31d2
Co-authored-by: Roman Stratiienko <r.stratiienko@gmail.com>
Signed-off-by: Dennis Tsiang <dennis.tsiang@arm.com>
Signed-off-by: Roman Stratiienko <r.stratiienko@gmail.com>
Signed-off-by: Normunds Rieksts <normunds.rieksts@arm.com>
Signed-off-by: Drew Davenport <ddavenport@google.com>
diff --git a/hwc3/Composer.h b/hwc3/Composer.h
new file mode 100644
index 0000000..b29d0cf
--- /dev/null
+++ b/hwc3/Composer.h
@@ -0,0 +1,41 @@
+/*
+ * Copyright (C) 2021 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 <aidl/android/hardware/graphics/composer3/BnComposer.h>
+#include <utils/Mutex.h>
+
+#include "ComposerClient.h"
+
+namespace aidl::android::hardware::graphics::composer3::impl {
+
+class Composer : public BnComposer {
+ public:
+  Composer() = default;
+
+  binder_status_t dump(int fd, const char** args, uint32_t num_args) override;
+
+  // compser3 api
+  ndk::ScopedAStatus createClient(
+      std::shared_ptr<IComposerClient>* client) override;
+  ndk::ScopedAStatus getCapabilities(std::vector<Capability>* caps) override;
+
+ protected:
+  ::ndk::SpAIBinder createBinder() override;
+};
+
+}  // namespace aidl::android::hardware::graphics::composer3::impl