Commit 37f81fa1 authored Sep 05, 2009 by Linus Torvalds

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 d945cb9c:
"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>

parent a2a8474c

drivers/char/n_tty.c

+1 −2

Original line number	Original line	Diff line number	Diff line
	@@ -300,8 +300,7 @@ static int do_output_char(unsigned char c, struct tty_struct *tty, int space)
	if (space < 2)		if (space < 2)
	return -1;		return -1;
	tty->canon_column = tty->column = 0;		tty->canon_column = tty->column = 0;
	tty_put_char(tty, '\r');		tty->ops->write(tty, "\r\n", 2);
	tty_put_char(tty, c);
	return 2;		return 2;
	}		}
	tty->canon_column = tty->column;		tty->canon_column = tty->column;