/***
  This file is part of systemd.

  Copyright 2010 Lennart Poettering

  systemd is free software; you can redistribute it and/or modify it
  under the terms of the GNU Lesser General Public License as published by
  the Free Software Foundation; either version 2.1 of the License, or
  (at your option) any later version.

  systemd is distributed in the hope that it will be useful, but
  WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  Lesser General Public License for more details.

  You should have received a copy of the GNU Lesser General Public License
  along with systemd; If not, see <http://www.gnu.org/licenses/>.
***/

#include <sys/ioctl.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <termios.h>
#include <unistd.h>
#include <fcntl.h>
#include <signal.h>
#include <time.h>
#include <assert.h>
#include <poll.h>
#include <linux/vt.h>
#include <linux/tiocl.h>
#include <linux/kd.h>

#include "terminal-util.h"
#include "time-util.h"
#include "process-util.h"
#include "util.h"
#include "fileio.h"
#include "path-util.h"

static volatile unsigned cached_columns = 0;
static volatile unsigned cached_lines = 0;

int open_terminal(const char *name, int mode) {
        int fd, r;
        unsigned c = 0;

        /*
         * If a TTY is in the process of being closed opening it might
         * cause EIO. This is horribly awful, but unlikely to be
         * changed in the kernel. Hence we work around this problem by
         * retrying a couple of times.
         *
         * https://bugs.launchpad.net/ubuntu/+source/linux/+bug/554172/comments/245
         */

        assert(!(mode & O_CREAT));

        for (;;) {
                fd = open(name, mode, 0);
                if (fd >= 0)
                        break;

                if (errno != EIO)
                        return -errno;

                /* Max 1s in total */
                if (c >= 20)
                        return -errno;

                usleep(50 * USEC_PER_MSEC);
                c++;
        }

        r = isatty(fd);
        if (r < 0) {
                safe_close(fd);
                return -errno;
        }

        if (!r) {
                safe_close(fd);
                return -ENOTTY;
        }

        return fd;
}