Add 'blank_screen' util.

This can be transitioned to by init to shutdown the
screen thereby preventing init from either depending
on binder or accessing halified sysnodes directly.

Bug: 70846424
Test: manual + init use
Change-Id: I86893ee5d7118547cd073297c0626e474f366b82

3 files changed, 87 insertions, 0 deletions

diff --git a/light/utils/Android.bp b/light/utils/Android.bp
new file mode 100644
index 000000000..ebcbfa27d
--- /dev/null
+++ b/light/utils/Android.bp
@@ -0,0 +1,30 @@
+//
+// Copyright (C) 2017 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.
+//
+
+// Turns off the screen.
+// Canonical usage is for init (which can't talk to hals directly).
+cc_binary {
+    name: "blank_screen",
+    init_rc: ["blank_screen.rc"],
+    srcs: ["main.cpp"],
+    shared_libs: [
+        "android.hardware.light@2.0",
+        "libbase",
+        "libhidlbase",
+        "libhidltransport",
+        "libutils",
+    ],
+}
diff --git a/light/utils/blank_screen.rc b/light/utils/blank_screen.rc
new file mode 100644
index 000000000..735551cc5
--- /dev/null
+++ b/light/utils/blank_screen.rc
@@ -0,0 +1,5 @@
+service blank_screen /system/bin/blank_screen
+    user system
+    oneshot
+    group system readproc
+    shutdown critical
diff --git a/light/utils/main.cpp b/light/utils/main.cpp
new file mode 100644
index 000000000..1f9cb9ce4
--- /dev/null
+++ b/light/utils/main.cpp
@@ -0,0 +1,52 @@
+/*
+ * Copyright (C) 2017 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.
+ */
+
+#include <iostream>
+#include <string>
+
+#include <android-base/logging.h>
+#include <android/hardware/light/2.0/ILight.h>
+
+void error(const std::string& msg) {
+    LOG(ERROR) << msg;
+    std::cerr << msg << std::endl;
+}
+
+int main() {
+    using ::android::hardware::light::V2_0::Brightness;
+    using ::android::hardware::light::V2_0::Flash;
+    using ::android::hardware::light::V2_0::ILight;
+    using ::android::hardware::light::V2_0::LightState;
+    using ::android::hardware::light::V2_0::Status;
+    using ::android::hardware::light::V2_0::Type;
+    using ::android::sp;
+
+    sp<ILight> service = ILight::getService();
+    if (service == nullptr) {
+        error("Could not retrieve light service.");
+        return -1;
+    }
+
+    const static LightState off = {
+        .color = 0u, .flashMode = Flash::NONE, .brightnessMode = Brightness::USER,
+    };
+
+    Status ret = service->setLight(Type::BACKLIGHT, off).withDefault(Status::UNKNOWN);
+    if (ret != Status::SUCCESS) {
+        error("Failed to shut off screen");
+    }
+    return 0;
+}