From f9a61f7dcbe1114b6a7d8d041c37c2ea56657571 Mon Sep 17 00:00:00 2001
From: Poul-Henning Kamp <phk@FreeBSD.org>
Date: Sun, 26 Feb 2012 20:56:49 +0000
Subject: [PATCH] Also call the low-level driver if ->c_iflag &
 (IXON|IXOFF|IXANY) changes.

Uftdi(4) examines (c_iflag & (IXON|IXOFF)) to control hw XON-XOFF support.
This is obviously no good, if changes to those bits are not communicated
down the stack.
---
 sys/kern/tty.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/sys/kern/tty.c b/sys/kern/tty.c
index 9a701d7ba2e8..8ca6bdf6a7c2 100644
--- a/sys/kern/tty.c
+++ b/sys/kern/tty.c
@@ -1481,6 +1481,8 @@ tty_generic_ioctl(struct tty *tp, u_long cmd, void *data, int fflag,
 		 */
 		if ((t->c_cflag & CIGNORE) == 0 &&
 		    (tp->t_termios.c_cflag != t->c_cflag ||
+		    ((tp->t_termios.c_iflag ^ t->c_iflag) &
+		    (IXON|IXOFF|IXANY)) ||
 		    tp->t_termios.c_ispeed != t->c_ispeed ||
 		    tp->t_termios.c_ospeed != t->c_ospeed)) {
 			error = ttydevsw_param(tp, t);