linux-kernel - [PATCH 3.16 196/370] USB: ch341: set tty baud speed according to tty struct

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Date:   Fri, 10 Mar 2017 11:46:23 +0000
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org,
        "Nicolas PLANEL" <nicolas.planel@...vance.com>,
        "Johan Hovold" <johan@...nel.org>
Subject: [PATCH 3.16 196/370] USB: ch341: set tty baud speed according to
 tty struct

3.16.42-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Nicolas PLANEL <nicolas.planel@...vance.com>

commit aa91def41a7bb1fd65492934ce6bea19202b6080 upstream.

The ch341_set_baudrate() function initialize the device baud speed
according to the value on priv->baud_rate. By default the ch341_open() set
it to a hardcoded value (DEFAULT_BAUD_RATE 9600). Unfortunately, the
tty_struct is not initialized with the same default value. (usually 56700)

This means that the tty_struct and the device baud rate generator are not
synchronized after opening the port.

Fixup is done by calling ch341_set_termios() if tty exist.
Remove unnecessary variable priv->baud_rate setup as it's already done by
ch341_port_probe().
Remove unnecessary call to ch341_set_{handshake,baudrate}() in
ch341_open() as there already called in ch341_configure() and
ch341_set_termios()

Signed-off-by: Nicolas PLANEL <nicolas.planel@...vance.com>
Signed-off-by: Johan Hovold <johan@...nel.org>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 drivers/usb/serial/ch341.c | 15 ++++++---------
 1 file changed, 6 insertions(+), 9 deletions(-)

diff --git a/drivers/usb/serial/ch341.c b/drivers/usb/serial/ch341.c
index 2d72aa3564a3..ede4f5fcfadd 100644
--- a/drivers/usb/serial/ch341.c
+++ b/drivers/usb/serial/ch341.c
@@ -84,6 +84,10 @@ struct ch341_private {
 	u8 line_status; /* active status of modem control inputs */
 };
 
+static void ch341_set_termios(struct tty_struct *tty,
+			      struct usb_serial_port *port,
+			      struct ktermios *old_termios);
+
 static int ch341_control_out(struct usb_device *dev, u8 request,
 			     u16 value, u16 index)
 {
@@ -309,19 +313,12 @@ static int ch341_open(struct tty_struct *tty, struct usb_serial_port *port)
 	struct ch341_private *priv = usb_get_serial_port_data(port);
 	int r;
 
-	priv->baud_rate = DEFAULT_BAUD_RATE;
-
 	r = ch341_configure(serial->dev, priv);
 	if (r)
 		goto out;
 
-	r = ch341_set_handshake(serial->dev, priv->line_control);
-	if (r)
-		goto out;
-
-	r = ch341_set_baudrate(serial->dev, priv);
-	if (r)
-		goto out;
+	if (tty)
+		ch341_set_termios(tty, port, NULL);
 
 	dev_dbg(&port->dev, "%s - submitting interrupt urb\n", __func__);
 	r = usb_submit_urb(port->interrupt_in_urb, GFP_KERNEL);