int tty_set_ldisc(struct tty_struct *tty, int ldisc)
{
int retval;
struct tty_ldisc *old_ldisc, *new_ldisc;
struct tty_struct *o_tty = tty->link;
new_ldisc = tty_ldisc_get(tty, ldisc);
if (IS_ERR(new_ldisc))
return PTR_ERR(new_ldisc);
retval = tty_ldisc_lock_pair_timeout(tty, o_tty, 5 * HZ);
if (retval) {
tty_ldisc_put(new_ldisc);
return retval;
}
/*
* Check the no-op case
*/
if (tty->ldisc->ops->num == ldisc) {
tty_ldisc_enable_pair(tty, o_tty);
tty_ldisc_put(new_ldisc);
return 0;
}
old_ldisc = tty->ldisc;
tty_lock(tty);
if (test_bit(TTY_HUPPING, &tty->flags) ||
test_bit(TTY_HUPPED, &tty->flags)) {
/* We were raced by the hangup method. It will have stomped
the ldisc data and closed the ldisc down */
tty_ldisc_enable_pair(tty, o_tty);
tty_ldisc_put(new_ldisc);
tty_unlock(tty);
return -EIO;
}
/* Shutdown the old discipline. */
tty_ldisc_close(tty, old_ldisc);
/* Now set up the new line discipline. */
tty->ldisc = new_ldisc;
tty_set_termios_ldisc(tty, ldisc);
retval = tty_ldisc_open(tty, new_ldisc);
if (retval < 0) {
/* Back to the old one or N_TTY if we can't */
tty_ldisc_put(new_ldisc);
tty_ldisc_restore(tty, old_ldisc);
}
if (tty->ldisc->ops->num != old_ldisc->ops->num && tty->ops->set_ldisc)
tty->ops->set_ldisc(tty);
/* At this point we hold a reference to the new ldisc and a
reference to the old ldisc, or we hold two references to
the old ldisc (if it was restored as part of error cleanup
above). In either case, releasing a single reference from
the old ldisc is correct. */
tty_ldisc_put(old_ldisc);
/*
* Allow ldisc referencing to occur again
*/
tty_ldisc_enable_pair(tty, o_tty);
/* Restart the work queue in case no characters kick it off. Safe if
already running */
schedule_work(&tty->port->buf.work);
if (o_tty)
schedule_work(&o_tty->port->buf.work);
tty_unlock(tty);
return retval;
}
void tty_ldisc_hangup(struct tty_struct *tty)
{
struct tty_ldisc *ld;
int reset = tty->driver->flags & TTY_DRIVER_RESET_TERMIOS;
int err = 0;
tty_ldisc_debug(tty, "closing ldisc: %p\n", tty->ldisc);
ld = tty_ldisc_ref(tty);
if (ld != NULL) {
if (ld->ops->flush_buffer)
ld->ops->flush_buffer(tty);
tty_driver_flush_buffer(tty);
if ((test_bit(TTY_DO_WRITE_WAKEUP, &tty->flags)) &&
ld->ops->write_wakeup)
ld->ops->write_wakeup(tty);
if (ld->ops->hangup)
ld->ops->hangup(tty);
tty_ldisc_deref(ld);
}
wake_up_interruptible_poll(&tty->write_wait, POLLOUT);
wake_up_interruptible_poll(&tty->read_wait, POLLIN);
tty_unlock(tty);
/*
* Shutdown the current line discipline, and reset it to
* N_TTY if need be.
*
* Avoid racing set_ldisc or tty_ldisc_release
*/
tty_ldisc_lock_pair(tty, tty->link);
tty_lock(tty);
if (tty->ldisc) {
/* At this point we have a halted ldisc; we want to close it and
reopen a new ldisc. We could defer the reopen to the next
open but it means auditing a lot of other paths so this is
a FIXME */
if (reset == 0) {
if (!tty_ldisc_reinit(tty, tty->termios.c_line))
err = tty_ldisc_open(tty, tty->ldisc);
else
err = 1;
}
/* If the re-open fails or we reset then go to N_TTY. The
N_TTY open cannot fail */
if (reset || err) {
BUG_ON(tty_ldisc_reinit(tty, N_TTY));
WARN_ON(tty_ldisc_open(tty, tty->ldisc));
}
}
tty_ldisc_enable_pair(tty, tty->link);
if (reset)
tty_reset_termios(tty);
tty_ldisc_debug(tty, "re-opened ldisc: %p\n", tty->ldisc);
}
int tty_set_ldisc(struct tty_struct *tty, int ldisc)
{
int retval;
struct tty_ldisc *o_ldisc, *new_ldisc;
struct tty_struct *o_tty = tty->link;
new_ldisc = tty_ldisc_get(tty, ldisc);
if (IS_ERR(new_ldisc))
return PTR_ERR(new_ldisc);
retval = tty_ldisc_lock_pair_timeout(tty, o_tty, 5 * HZ);
if (retval) {
tty_ldisc_put(new_ldisc);
return retval;
}
/*
* Check the no-op case
*/
if (tty->ldisc->ops->num == ldisc) {
tty_ldisc_enable_pair(tty, o_tty);
tty_ldisc_put(new_ldisc);
return 0;
}
/* FIXME: why 'shutoff' input if the ldisc is locked? */
tty->receive_room = 0;
o_ldisc = tty->ldisc;
tty_lock(tty);
/* FIXME: for testing only */
WARN_ON(test_bit(TTY_HUPPED, &tty->flags));
if (test_bit(TTY_HUPPING, &tty->flags)) {
/* We were raced by the hangup method. It will have stomped
the ldisc data and closed the ldisc down */
tty_ldisc_enable_pair(tty, o_tty);
tty_ldisc_put(new_ldisc);
tty_unlock(tty);
return -EIO;
}
/* Shutdown the current discipline. */
tty_ldisc_close(tty, o_ldisc);
/* Now set up the new line discipline. */
tty->ldisc = new_ldisc;
tty_set_termios_ldisc(tty, ldisc);
retval = tty_ldisc_open(tty, new_ldisc);
if (retval < 0) {
/* Back to the old one or N_TTY if we can't */
tty_ldisc_put(new_ldisc);
tty_ldisc_restore(tty, o_ldisc);
}
/* At this point we hold a reference to the new ldisc and a
a reference to the old ldisc. If we ended up flipping back
to the existing ldisc we have two references to it */
if (tty->ldisc->ops->num != o_ldisc->ops->num && tty->ops->set_ldisc)
tty->ops->set_ldisc(tty);
tty_ldisc_put(o_ldisc);
/*
* Allow ldisc referencing to occur again
*/
tty_ldisc_enable_pair(tty, o_tty);
/* Restart the work queue in case no characters kick it off. Safe if
already running */
schedule_work(&tty->port->buf.work);
if (o_tty)
schedule_work(&o_tty->port->buf.work);
tty_unlock(tty);
return retval;
}
