tty: Remove chars_in_buffer() line discipline method

The chars_in_buffer() line discipline method serves no functional
purpose, other than as a (dubious) debugging aid for mostly bit-rotting
drivers. Despite being documented as an optional method, every caller
is unconditionally executed (although conditionally compiled).
Furthermore, direct tty->ldisc access without an ldisc ref is unsafe.
Lastly, N_TTY's chars_in_buffer() has warned of removal since 3.12.

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 0 insertions, 3 deletions

diff --git a/Documentation/serial/tty.txt b/Documentation/serial/tty.txt
index bc3842dc323a..798cba82c762 100644
--- a/Documentation/serial/tty.txt
+++ b/Documentation/serial/tty.txt
@@ -72,9 +72,6 @@ flush_buffer()	-	(optional) May be called at any point between
                         open and close, and instructs the line discipline
                         to empty its input buffer.
 
-chars_in_buffer() -     (optional) Report the number of bytes in the input
-                        buffer.
-
 set_termios()   -       (optional) Called on termios structure changes.
                         The caller passes the old termios data and the
                         current data is in the tty. Called under the