libcamera: Add Process and ProcessManager classes

Add a Process class to abstract a process, and a ProcessManager singleton
to monitor and manage the processes.

Signed-off-by: Paul Elder <paul.elder@ideasonboard.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

test/process/process_test.cpp

@@ -0,0 +1,100 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/*
+ * Copyright (C) 2019, Google Inc.
+ *
+ * process_test.cpp - Process test
+ */
+
+#include <iostream>
+#include <unistd.h>
+#include <vector>
+
+#include <libcamera/camera_manager.h>
+#include <libcamera/event_dispatcher.h>
+#include <libcamera/timer.h>
+
+#include "process.h"
+#include "test.h"
+#include "utils.h"
+
+using namespace std;
+using namespace libcamera;
+
+class ProcessTestChild
+{
+public:
+	int run(int status)
+	{
+		usleep(50000);
+
+		return status;
+	}
+};
+
+class ProcessTest : public Test
+{
+public:
+	ProcessTest()
+	{
+	}
+
+protected:
+	int run()
+	{
+		EventDispatcher *dispatcher = CameraManager::instance()->eventDispatcher();
+		Timer timeout;
+
+		int exitCode = 42;
+		vector<std::string> args;
+		args.push_back(to_string(exitCode));
+		int ret = proc_.start("/proc/self/exe", args);
+		if (ret) {
+			cerr << "failed to start process" << endl;
+			return TestFail;
+		}
+		proc_.finished.connect(this, &ProcessTest::procFinished);
+
+		timeout.start(100);
+		while (timeout.isRunning())
+			dispatcher->processEvents();
+
+		if (exitStatus_ != Process::NormalExit) {
+			cerr << "process did not exit normally" << endl;
+			return TestFail;
+		}
+
+		if (exitCode != exitCode_) {
+			cerr << "exit code should be " << exitCode
+			     << ", actual is " << exitCode_ << endl;
+			return TestFail;
+		}
+
+		return TestPass;
+	}
+
+private:
+	void procFinished(Process *proc, enum Process::ExitStatus exitStatus, int exitCode)
+	{
+		exitStatus_ = exitStatus;
+		exitCode_ = exitCode;
+	}
+
+	Process proc_;
+	enum Process::ExitStatus exitStatus_;
+	int exitCode_;
+};
+
+/*
+ * Can't use TEST_REGISTER() as single binary needs to act as both
+ * parent and child processes.
+ */
+int main(int argc, char **argv)
+{
+	if (argc == 2) {
+		int status = std::stoi(argv[1]);
+		ProcessTestChild child;
+		return child.run(status);
+	}
+
+	return ProcessTest().execute();
+}