tty: gigaset: really fix chars_in_buffer

The tty_operation chars_in_buffer() is not allowed to return a negative
value to signal an error.  Corrects the problem flagged by commit
23198fda7182969b619613a555f8645fdc3dc334, "tty: fix chars_in_buffers".

Signed-off-by: Tilman Schmidt <tilman@imap.cc>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: stable <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 7 insertions, 12 deletions

diff --git a/drivers/isdn/gigaset/interface.c b/drivers/isdn/gigaset/interface.c
index 8ff7e35c7069..f33ac27de643 100644
--- a/drivers/isdn/gigaset/interface.c
+++ b/drivers/isdn/gigaset/interface.c
@@ -408,33 +408,28 @@ static int if_write_room(struct tty_struct *tty)
         return retval;
 }
 
-/* FIXME: This function does not have error returns */
-
 static int if_chars_in_buffer(struct tty_struct *tty)
 {
         struct cardstate *cs;
-        int retval = -ENODEV;
+        int retval = 0;
 
         cs = (struct cardstate *) tty->driver_data;
         if (!cs) {
                 pr_err("%s: no cardstate\n", __func__);
-                return -ENODEV;
+                return 0;
         }
 
         gig_dbg(DEBUG_IF, "%u: %s()", cs->minor_index, __func__);
 
-        if (mutex_lock_interruptible(&cs->mutex))
-                return -ERESTARTSYS; // FIXME -EINTR?
+        mutex_lock(&cs->mutex);
 
-        if (!cs->connected) {
+        if (!cs->connected)
                 gig_dbg(DEBUG_IF, "not connected");
-                retval = -ENODEV;
-        } else if (!cs->open_count)
+        else if (!cs->open_count)
                 dev_warn(cs->dev, "%s: device not opened\n", __func__);
-        else if (cs->mstate != MS_LOCKED) {
+        else if (cs->mstate != MS_LOCKED)
                 dev_warn(cs->dev, "can't write to unlocked device\n");
-                retval = -EBUSY;
-        } else
+        else
                 retval = cs->ops->chars_in_buffer(cs);
 
         mutex_unlock(&cs->mutex);