From 37f81fa1f63ad38e16125526bb2769ae0ea8d332 Mon Sep 17 00:00:00 2001
From: Linus Torvalds <torvalds@linux-foundation.org>
Date: Sat, 5 Sep 2009 12:46:07 -0700
Subject: [PATCH] n_tty: do O_ONLCR translation as a single write

When translating CR to CRNL in the n_tty line discipline, we did it as
two tty_put_char() calls.  Which works, but is stupid, and has caused
problems before too with bad interactions with the write_room() logic.
The generic USB serial driver had that problem, for example.

Now the pty layer had similar issues after being moved to the generic
tty buffering code (in commit d945cb9cce20ac7143c2de8d88b187f62db99bdc:
"pty: Rework the pty layer to use the normal buffering logic").

So stop doing the silly separate two writes, and do it as a single write
instead.  That's what the n_tty layer already does for the space
expansion of tabs (XTABS), and it means that we'll now always have just
a single write for the CRNL to match the single 'tty_write_room()' test,
which hopefully means that the next time somebody screws up buffering,
it won't cause weeks of debugging.

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---
 drivers/char/n_tty.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/drivers/char/n_tty.c b/drivers/char/n_tty.c
index 973be2f44195..4e28b35024ec 100644
--- a/drivers/char/n_tty.c
+++ b/drivers/char/n_tty.c
@@ -300,8 +300,7 @@ static int do_output_char(unsigned char c, struct tty_struct *tty, int space)
 			if (space < 2)
 				return -1;
 			tty->canon_column = tty->column = 0;
-			tty_put_char(tty, '\r');
-			tty_put_char(tty, c);
+			tty->ops->write(tty, "\r\n", 2);
 			return 2;
 		}
 		tty->canon_column = tty->column;
-- 
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