tty: Use flow-control char function on closing path

Use n_tty_receive_char_flow_ctrl also on the closing path. This makes
the code cleaner and consistent.

However, there a small change of regression!

The earlier closing path has a small difference compared with the
normal receive path. If START_CHAR and STOP_CHAR are equal, their
precedence is different depending on which path a character is
processed. I don't know whether this difference was intentional or
not, and if equal START_CHAR and STOP_CHAR is actually used anywhere.
But it feels not so useful corner case.

While this change would logically belong to those earlier changes,
having a separate patch for this is useful. If this regresses, bisect
can pinpoint this change rather than the large patch. Also, this
change is not necessary to minimal fix for the issue addressed in
the previous patch.

Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Link: https://lore.kernel.org/r/20220606153652.63554-3-ilpo.jarvinen@linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/tty/n_tty.c b/drivers/tty/n_tty.c
index 8d80384df87441b4c09fe4f8716c2bb7772f4344..3afdd9033a9c50b82b9f6e5c33471c7d908afed9 100644 (file)
--- a/drivers/tty/n_tty.c
+++ b/drivers/tty/n_tty.c
@@ -1434,15 +1434,10 @@ static void n_tty_receive_char_closing(struct tty_struct *tty, unsigned char c,
                c = tolower(c);
 
        if (I_IXON(tty)) {
-               if (c == STOP_CHAR(tty)) {
-                       if (!lookahead_done)
-                               stop_tty(tty);
-               } else if (c == START_CHAR(tty) && lookahead_done) {
-                       return;
-               } else if (c == START_CHAR(tty) ||
-                        (tty->flow.stopped && !tty->flow.tco_stopped && I_IXANY(tty) &&
-                         c != INTR_CHAR(tty) && c != QUIT_CHAR(tty) &&
-                         c != SUSP_CHAR(tty))) {
+               if (!n_tty_receive_char_flow_ctrl(tty, c, lookahead_done) &&
+                   tty->flow.stopped && !tty->flow.tco_stopped && I_IXANY(tty) &&
+                   c != INTR_CHAR(tty) && c != QUIT_CHAR(tty) &&
+                   c != SUSP_CHAR(tty)) {
                        start_tty(tty);
                        process_echoes(tty);
                }