0001-usb-serial-ch341-Add-parity-support.patch

From 826333457d90018641883265a672268e1b13ab93 Mon Sep 17 00:00:00 2001
From: Karl Palsson <karlp@tweak.net.au>
Date: Tue, 18 Mar 2014 23:33:27 +0000
Subject: [PATCH] usb/serial/ch341: Add parity support

Based on wireshark packet traces from a windows machine.

ch340 and ch341 both seem to support all parity modes, but only the ch341
appears to support variable data bits and variable stop bits, so those are left
unimplemented, as before.

Tested on a generic usb-rs485 dongle with the chip label scratched off, and
some Modbus/RTU devices that required various parity settings.

Signed-off-by: Karl Palsson <karlp@tweak.net.au>
---
 drivers/usb/serial/ch341.c | 27 ++++++++++++++++++++++++++-
 1 file changed, 26 insertions(+), 1 deletion(-)

diff --git a/drivers/usb/serial/ch341.c b/drivers/usb/serial/ch341.c
index 82371f6..afd2ec4 100644
--- a/drivers/usb/serial/ch341.c
+++ b/drivers/usb/serial/ch341.c
@@ -346,6 +346,7 @@ static void ch341_set_termios(struct tty_struct *tty,
 	struct ch341_private *priv = usb_get_serial_port_data(port);
 	unsigned baud_rate;
 	unsigned long flags;
+	unsigned int par_flags;
 
 	baud_rate = tty_get_baud_rate(tty);
 
@@ -366,9 +367,33 @@ static void ch341_set_termios(struct tty_struct *tty,
 
 	/* Unimplemented:
 	 * (cflag & CSIZE) : data bits [5, 8]
-	 * (cflag & PARENB) : parity {NONE, EVEN, ODD}
 	 * (cflag & CSTOPB) : stop bits [1, 2]
 	 */
+	/* CH340 doesn't appear to support variable stop bits or data bits */
+	if (C_PARENB(tty)) {
+		if (C_PARODD(tty)) {
+			if (tty->termios.c_cflag & CMSPAR) {
+				dev_dbg(&port->dev, "parity = mark\n");
+				par_flags = 0xeb;
+			} else {
+				dev_dbg(&port->dev, "parity = odd\n");
+				par_flags = 0xcb;
+			}
+		} else {
+			if (tty->termios.c_cflag & CMSPAR) {
+				dev_dbg(&port->dev, "parity = space\n");
+				par_flags = 0xfb;
+			} else {
+				dev_dbg(&port->dev, "parity = even\n");
+				par_flags = 0xdb;
+			}
+		}
+	} else {
+		dev_dbg(&port->dev, "parity = none\n");
+		par_flags = 0xc3;
+	}
+	ch341_control_out(port->serial->dev, 0x9a, 0x2518, par_flags);
+
 }
 
 static void ch341_break_ctl(struct tty_struct *tty, int break_state)
-- 
1.8.3.1