usb : serial : ch341 : set tty baud speed according to tty struct

[Nicolas PLANEL <nicolas.planel@xxxxxxxxxxxx>]

    Hi,


According to git log your are currently the two maintainer of the ch341 
usb serial driver.

Thanks to pyserial, that did not initialize the serial port speed like 
minicom.
Basically pyserial only set the port speed (calling TIOCSSERIAL ioctl) 
if the user request a different value different currently used. 
(TIOCGSERIAL)

A long sentence in short code :

if ser.baudrate != user_requested_baudrate:
   ser.baudrate = user_requested_baudrate

In short, if the python code open a serial port at a speed of 57600 
baud, the hw speed line will be in reality at 9600 baud. (driver default 
speed)


Regards,

Nicolas PLANEL

===
From 16df0d507a653c48f757635f717f2ba886f8c5ff Mon Sep 17 00:00:00 2001
From: Nicolas PLANEL <nicolas.planel@xxxxxxxxxxxx>
Date: Tue, 17 Feb 2015 00:59:14 -0500
Subject: [PATCH] USB: ch341: set tty baud speed according to tty struct

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 elementary simple by calling tty_get_baud_rate() and
tty_encode_baud_rate() helper to sync up the baud rate during the
ch341_open() call.
---
 drivers/usb/serial/ch341.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/drivers/usb/serial/ch341.c b/drivers/usb/serial/ch341.c
index 2d72aa3..2dbbbf6 100644
--- a/drivers/usb/serial/ch341.c
+++ b/drivers/usb/serial/ch341.c
@@ -307,9 +307,13 @@ static int ch341_open(struct tty_struct *tty, 
struct usb_serial_port *port)
 {
     struct usb_serial *serial = port->serial;
     struct ch341_private *priv = usb_get_serial_port_data(port);
+    unsigned baud;
     int r;

     priv->baud_rate = DEFAULT_BAUD_RATE;
+    baud = tty_get_baud_rate(tty);
+    if (baud)
+        priv->baud_rate = baud;

     r = ch341_configure(serial->dev, priv);
     if (r)
@@ -323,6 +327,9 @@ static int ch341_open(struct tty_struct *tty, struct 
usb_serial_port *port)
     if (r)
         goto out;

+    baud = priv->baud_rate;
+    tty_encode_baud_rate(tty, baud, baud);
+
     dev_dbg(&port->dev, "%s - submitting interrupt urb\n", __func__);
     r = usb_submit_urb(port->interrupt_in_urb, GFP_KERNEL);
     if (r) {
--
1.9.1




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