n_tty: do O_ONLCR translation as a single write

torvalds · torvalds · commit 37f81fa1f63a · 2009-09-05T12:46:07.000-07:00
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 d945cb9: "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>
diff --git 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;
