Merge branch 'work.misc' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs

[karo-tx-linux.git] / drivers / tty / tty_ldisc.c

diff --git a/drivers/tty/tty_ldisc.c b/drivers/tty/tty_ldisc.c
index e4603b09863a8fa5ffd4467e81a463538f0533bb..2fe216b276e29ee54d6dd804555f27668407875a 100644 (file)
--- a/drivers/tty/tty_ldisc.c
+++ b/drivers/tty/tty_ldisc.c
@@ -491,6 +491,29 @@ static void tty_ldisc_close(struct tty_struct *tty, struct tty_ldisc *ld)
        tty_ldisc_debug(tty, "%p: closed\n", ld);
 }
 
+/**
+ *     tty_ldisc_failto        -       helper for ldisc failback
+ *     @tty: tty to open the ldisc on
+ *     @ld: ldisc we are trying to fail back to
+ *
+ *     Helper to try and recover a tty when switching back to the old
+ *     ldisc fails and we need something attached.
+ */
+
+static int tty_ldisc_failto(struct tty_struct *tty, int ld)
+{
+       struct tty_ldisc *disc = tty_ldisc_get(tty, ld);
+       int r;
+
+       if (IS_ERR(disc))
+               return PTR_ERR(disc);
+       tty->ldisc = disc;
+       tty_set_termios_ldisc(tty, ld);
+       if ((r = tty_ldisc_open(tty, disc)) < 0)
+               tty_ldisc_put(disc);
+       return r;
+}
+
 /**
  *     tty_ldisc_restore       -       helper for tty ldisc change
  *     @tty: tty to recover
@@ -502,9 +525,6 @@ static void tty_ldisc_close(struct tty_struct *tty, struct tty_ldisc *ld)
 
 static void tty_ldisc_restore(struct tty_struct *tty, struct tty_ldisc *old)
 {
-       struct tty_ldisc *new_ldisc;
-       int r;
-
        /* There is an outstanding reference here so this is safe */
        old = tty_ldisc_get(tty, old->ops->num);
        WARN_ON(IS_ERR(old));
@@ -512,17 +532,13 @@ static void tty_ldisc_restore(struct tty_struct *tty, struct tty_ldisc *old)
        tty_set_termios_ldisc(tty, old->ops->num);
        if (tty_ldisc_open(tty, old) < 0) {
                tty_ldisc_put(old);
-               /* This driver is always present */
-               new_ldisc = tty_ldisc_get(tty, N_TTY);
-               if (IS_ERR(new_ldisc))
-                       panic("n_tty: get");
-               tty->ldisc = new_ldisc;
-               tty_set_termios_ldisc(tty, N_TTY);
-               r = tty_ldisc_open(tty, new_ldisc);
-               if (r < 0)
-                       panic("Couldn't open N_TTY ldisc for "
-                             "%s --- error %d.",
-                             tty_name(tty), r);
+               /* The traditional behaviour is to fall back to N_TTY, we
+                  want to avoid falling back to N_NULL unless we have no
+                  choice to avoid the risk of breaking anything */
+               if (tty_ldisc_failto(tty, N_TTY) < 0 &&
+                   tty_ldisc_failto(tty, N_NULL) < 0)
+                       panic("Couldn't open N_NULL ldisc for %s.",
+                             tty_name(tty));
        }
 }
 
@@ -605,6 +621,7 @@ err:
        tty_unlock(tty);
        return retval;
 }
+EXPORT_SYMBOL_GPL(tty_set_ldisc);
 
 /**
  *     tty_ldisc_kill  -       teardown ldisc
@@ -797,6 +814,7 @@ void tty_ldisc_release(struct tty_struct *tty)
 
        tty_ldisc_debug(tty, "released\n");
 }
+EXPORT_SYMBOL_GPL(tty_ldisc_release);
 
 /**
  *     tty_ldisc_init          -       ldisc setup for new tty