TakeControl.c

// SPDX-License-Identifier: GPL-2.0
// This is garbage code
#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/sysmacros.h>
#include <systemd/sd-bus.h>

static sd_bus * bus;

static int ConnectBus(void)
{
	int r;
	/* Connect to the system bus */
	r = sd_bus_open_system(&bus);
	if (r < 0) {
		fprintf(stderr, "Failed to connect to system bus: %s\n", strerror(-r));
		return 0;
	}
	return 1;
}

static void DisconnectBus(void)
{
	sd_bus_unref(bus);
}

static int TakeControl(void)
{
	sd_bus_error error = SD_BUS_ERROR_NULL;
	sd_bus_message *m = NULL;
	int r;


	/* Issue the method call and store the respons message in m */
	r = sd_bus_call_method(bus,
		"org.freedesktop.login1",                   /* service to contact */
		"/org/freedesktop/login1/session/auto",     /* object path */
		"org.freedesktop.login1.Session",           /* interface name */
		"TakeControl",                              /* method name */
		&error,                                     /* object to return error in */
		&m,                                         /* return message on success */
		"b",                                        /* input signature */
		0);                                         /* first argument */
	if (r < 0) {
		fprintf(stderr, "Failed to issue method call: %s\n", error.message);
		return 0;
	}
	sd_bus_error_free(&error);
	sd_bus_message_unref(m);
	return 1;
}

const int TakeDevice(int maj, int min)
{
	sd_bus_error error = SD_BUS_ERROR_NULL;
	sd_bus_message *m = NULL;
	const int fd;
	int r;

	/* Issue the method call and store the respons message in m */
	r = sd_bus_call_method(bus,
		"org.freedesktop.login1",                  /* service to contact */
		"/org/freedesktop/login1/session/auto",    /* object path */
		"org.freedesktop.login1.Session",          /* interface name */
		"TakeDevice",                              /* method name */
		&error,                                    /* object to return error in */
		&m,                                        /* return message on success */
		"uu",                                      /* input signature */
		maj,                                      /* first argument */
		min);                                      /* second argument */
	if (r < 0) {
		fprintf(stderr, "Failed to issue method call: %s\n", error.message);
		return 0;
	}

	/* Parse the response message */
	r = sd_bus_message_read(m, "h", &fd);
	if (r < 0) {
		fprintf(stderr, "Failed to parse response message: %s\n", strerror(-r));
		return 0;
	}
	sd_bus_error_free(&error);
	sd_bus_message_unref(m);
	return fd;
}

int main(void)
{
	struct stat s;
	stat("/dev/input/event2", &s);
	printf("maj = %x, min = %x\n", major(s.st_rdev), minor(s.st_rdev));

	if (ConnectBus()) {
		if (TakeControl())
			TakeDevice(major(s.st_rdev), minor(s.st_rdev));
		DisconnectBus();
	}
	return 0;
}