tests: Introduce hotplug hot-unplug unit test

This test checks the code-paths for camera's hotplugged and
unplugged support. It is based on bind/unbind of a UVC device
from sysfs. Hence, this test requires root permissions to run
and should have at least one already bound UVC device present
in the system.

Signed-off-by: Umang Jain <email@uajain.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

test/hotplug-cameras.cpp

@@ -0,0 +1,128 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/*
+ * Copyright (C) 2020, Umang Jain <email@uajain.com>
+ *
+ * hotplug-cameras.cpp - Test cameraAdded/cameraRemoved signals in CameraManager
+ */
+
+#include <dirent.h>
+#include <fstream>
+#include <iostream>
+#include <string.h>
+#include <unistd.h>
+
+#include <libcamera/camera.h>
+#include <libcamera/camera_manager.h>
+#include <libcamera/event_dispatcher.h>
+#include <libcamera/timer.h>
+
+#include "libcamera/internal/file.h"
+#include "libcamera/internal/thread.h"
+
+#include "test.h"
+
+using namespace libcamera;
+
+class HotplugTest : public Test
+{
+protected:
+	void cameraAddedHandler(std::shared_ptr<Camera> cam)
+	{
+		cameraAdded_ = true;
+	}
+
+	void cameraRemovedHandler(std::shared_ptr<Camera> cam)
+	{
+		cameraRemoved_ = true;
+	}
+
+	int init()
+	{
+		if (!File::exists("/sys/module/uvcvideo")) {
+			std::cout << "uvcvideo driver is not loaded, skipping" << std::endl;
+			return TestSkip;
+		}
+
+		if (geteuid() != 0) {
+			std::cout << "This test requires root permissions, skipping" << std::endl;
+			return TestSkip;
+		}
+
+		cm_ = new CameraManager();
+		if (cm_->start()) {
+			std::cout << "Failed to start camera manager" << std::endl;
+			return TestFail;
+		}
+
+		cameraAdded_ = false;
+		cameraRemoved_ = false;
+
+		cm_->cameraAdded.connect(this, &HotplugTest::cameraAddedHandler);
+		cm_->cameraRemoved.connect(this, &HotplugTest::cameraRemovedHandler);
+
+		return 0;
+	}
+
+	int run()
+	{
+		DIR *dir;
+		struct dirent *dirent;
+		std::string uvcDeviceDir;
+
+		dir = opendir(uvcDriverDir_.c_str());
+		/* Find a UVC device directory, which we can bind/unbind. */
+		while ((dirent = readdir(dir)) != nullptr) {
+			if (!File::exists(uvcDriverDir_ + dirent->d_name + "/video4linux"))
+				continue;
+
+			uvcDeviceDir = dirent->d_name;
+			break;
+		}
+		closedir(dir);
+
+		/* If no UVC device found, skip the test. */
+		if (uvcDeviceDir.empty())
+			return TestSkip;
+
+		/* Unbind a camera and process events. */
+		std::ofstream(uvcDriverDir_ + "unbind", std::ios::binary)
+			<< uvcDeviceDir;
+		Timer timer;
+		timer.start(1000);
+		while (timer.isRunning() && !cameraRemoved_)
+			Thread::current()->eventDispatcher()->processEvents();
+		if (!cameraRemoved_) {
+			std::cout << "Camera unplug not detected" << std::endl;
+			return TestFail;
+		}
+
+		/* Bind the camera again and process events. */
+		std::ofstream(uvcDriverDir_ + "bind", std::ios::binary)
+			<< uvcDeviceDir;
+		timer.start(1000);
+		while (timer.isRunning() && !cameraAdded_)
+			Thread::current()->eventDispatcher()->processEvents();
+		if (!cameraAdded_) {
+			std::cout << "Camera plug not detected" << std::endl;
+			return TestFail;
+		}
+
+		return TestPass;
+	}
+
+	void cleanup()
+	{
+		cm_->stop();
+		delete cm_;
+	}
+
+private:
+	CameraManager *cm_;
+	static const std::string uvcDriverDir_;
+	bool cameraRemoved_;
+	bool cameraAdded_;
+};
+
+const std::string HotplugTest::uvcDriverDir_ = "/sys/bus/usb/drivers/uvcvideo/";
+
+TEST_REGISTER(HotplugTest)