linux-kernel - [PATCH v3 2/5] tty: Simplify receive flow control char logic

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Message-Id: <20220411094859.10894-3-ilpo.jarvinen@linux.intel.com>
Date:   Mon, 11 Apr 2022 12:48:56 +0300
From:   Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
To:     linux-serial@...r.kernel.org, Greg KH <gregkh@...uxfoundation.org>,
        Jiri Slaby <jirislaby@...nel.org>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc:     linux-kernel@...r.kernel.org,
        Gilles Buloz <gilles.buloz@...tron.com>,
        Johan Hovold <johan@...nel.org>,
        Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
Subject: [PATCH v3 2/5] tty: Simplify receive flow control char logic

Add a helper to check if the character is a flow control one.
Reorder return places, add else for the case where START_CHAR
and STOP_CHAR are the same, w/o else both would match.

This seems cleanest approach once skipping due to lookahead
is added by the next patch. Its downside is the duplicated
START_CHAR and STOP_CHAR checks.

Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
---
 drivers/tty/n_tty.c | 15 ++++++++++-----
 1 file changed, 10 insertions(+), 5 deletions(-)

diff --git a/drivers/tty/n_tty.c b/drivers/tty/n_tty.c
index c7edfc001fd0..90b3e06cbeb1 100644
--- a/drivers/tty/n_tty.c
+++ b/drivers/tty/n_tty.c
@@ -1220,20 +1220,25 @@ n_tty_receive_signal_char(struct tty_struct *tty, int signal, unsigned char c)
 		process_echoes(tty);
 }
 
+static bool n_tty_is_char_flow_ctrl(struct tty_struct *tty, unsigned char c)
+{
+	return c == START_CHAR(tty) || c == STOP_CHAR(tty);
+}
+
 /* Returns true if c is consumed as flow-control character */
 static bool n_tty_receive_char_flow_ctrl(struct tty_struct *tty, unsigned char c)
 {
+	if (!n_tty_is_char_flow_ctrl(tty, c))
+		return false;
+
 	if (c == START_CHAR(tty)) {
 		start_tty(tty);
 		process_echoes(tty);
-		return true;
-	}
-	if (c == STOP_CHAR(tty)) {
+	} else if (c == STOP_CHAR(tty)) {
 		stop_tty(tty);
-		return true;
 	}
 
-	return false;
+	return true;
 }
 
 static void n_tty_receive_char_special(struct tty_struct *tty, unsigned char c)
-- 
2.30.2