lshal: add wait command

Waits for an interface to start (e.g. for scripting certain tests).

Fixes: 135956088
Test: the following
$ adb shell lshal wait android.hardware.nfc@1.0::INfc/foo
Service not found (missing permissions or not in VINTF manifest?).
$ echo $?
128
$ adb shell lshal wait android.hardware.nfc@1.0::INfc/default
$ echo $?
0
Test: lshal_test

Change-Id: I355fc33f9e46bac573a38425205e8db81f19a36e
diff --git a/cmds/lshal/WaitCommand.cpp b/cmds/lshal/WaitCommand.cpp
new file mode 100644
index 0000000..65b41b9
--- /dev/null
+++ b/cmds/lshal/WaitCommand.cpp
@@ -0,0 +1,87 @@
+/*
+ * Copyright (C) 2019 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 "WaitCommand.h"
+
+#include "Lshal.h"
+
+#include <hidl/ServiceManagement.h>
+#include <hidl-util/FQName.h>
+
+namespace android {
+namespace lshal {
+
+std::string WaitCommand::getName() const {
+    return "wait";
+}
+
+std::string WaitCommand::getSimpleDescription() const {
+    return "Wait for HAL to start if it is not already started.";
+}
+
+Status WaitCommand::parseArgs(const Arg &arg) {
+    if (optind + 1 != arg.argc) {
+        return USAGE;
+    }
+
+    mInterfaceName = arg.argv[optind];
+    ++optind;
+    return OK;
+}
+
+Status WaitCommand::main(const Arg &arg) {
+    Status status = parseArgs(arg);
+    if (status != OK) {
+        return status;
+    }
+
+    auto [interface, instance] = splitFirst(mInterfaceName, '/');
+    instance = instance.empty() ? "default" : instance;
+
+    FQName fqName;
+    if (!FQName::parse(interface, &fqName) || fqName.isIdentifier() || !fqName.isFullyQualified()) {
+        mLshal.err() << "Invalid fully-qualified name '" << interface << "'\n\n";
+        return USAGE;
+    }
+
+    using android::hidl::manager::V1_0::IServiceManager;
+
+    using android::hardware::details::getRawServiceInternal;
+    auto service = getRawServiceInternal(interface, instance, true /*retry*/, false /*getStub*/);
+
+    if (service == nullptr) {
+        mLshal.err() << "Service not found (missing permissions or not in VINTF manifest?).\n";
+        return NO_INTERFACE;
+    }
+
+    return OK;
+}
+
+void WaitCommand::usage() const {
+    static const std::string debug =
+            "wait:\n"
+            "    lshal wait <interface/instance> \n"
+            "        For a HAL that is on the device, wait for the HAL to start.\n"
+            "        This will not start a HAL unless it is configured as a lazy HAL.\n"
+            "        <interface>: Format is `android.hardware.foo@1.0::IFoo/default`.\n"
+            "            If instance name is missing `default` is used.\n";
+
+    mLshal.err() << debug;
+}
+
+}  // namespace lshal
+}  // namespace android
+