Find core keybaord device id with XKB only

gistfile1.c

static int
get_core_kbd_device_id(struct app *app, uint8_t *out)
{
    xcb_xkb_get_device_info_cookie_t cookie;
    _cleanup_free_ xcb_xkb_get_device_info_reply_t *reply = NULL;

    cookie = xcb_xkb_get_device_info(app->conn,
                                     XCB_XKB_ID_USE_CORE_KBD,
                                     0, 0, 0, 0, 0, 0);

    reply = xcb_xkb_get_device_info_reply(app->conn, cookie, NULL);
    if (!reply) {
        warnx("couldn't get core keyboard xkb device info");
        return -EFAULT;
    }

    *out = reply->deviceID;
    return 0;
}