3.16.44-rc1 review patch. If anyone has any objections, please let me know.
------------------
From: Johan Hovold <johan@xxxxxxxxxx>
commit a0467a967f347842b30739aae636c44980265265 upstream.
The modem-status register was read as part of device configuration at
port_probe and then again at open (and reset-resume). During open (and
reset-resume) the MSR was read before submitting the interrupt URB,
something which could lead to an MSR-change going unnoticed when it
races with open (reset-resume).
Fix this by dropping the redundant reconfiguration of the port at every
open, and only read the MSR after the interrupt URB has been submitted.
Fixes: 664d5df92e88 ("USB: usb-serial ch341: support for DTR/RTS/CTS")
Signed-off-by: Johan Hovold <johan@xxxxxxxxxx>
[bwh: Backported to 3.16: adjust context]
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
drivers/usb/serial/ch341.c | 27 ++++++++++++---------------
1 file changed, 12 insertions(+), 15 deletions(-)
--- a/drivers/usb/serial/ch341.c
+++ b/drivers/usb/serial/ch341.c
@@ -246,21 +246,11 @@ static int ch341_configure(struct usb_de
if (r < 0)
goto out;
- /* expect 0xff 0xee */
- r = ch341_get_status(dev, priv);
- if (r < 0)
- goto out;
-
r = ch341_set_baudrate_lcr(dev, priv, 0);
if (r < 0)
goto out;
r = ch341_set_handshake(dev, priv->line_control);
- if (r < 0)
- goto out;
-
- /* expect 0x9f 0xee */
- r = ch341_get_status(dev, priv);
out: kfree(buffer);
return r;
@@ -332,14 +322,9 @@ static void ch341_close(struct usb_seria
/* open this device, set default parameters */
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);
int r;
- r = ch341_configure(serial->dev, priv);
- if (r)
- return r;
-
if (tty)
ch341_set_termios(tty, port, NULL);
@@ -351,6 +336,12 @@ static int ch341_open(struct tty_struct
return r;
}
+ r = ch341_get_status(port->serial->dev, priv);
+ if (r < 0) {
+ dev_err(&port->dev, "failed to read modem status: %d\n", r);
+ goto err_kill_interrupt_urb;
+ }
+
r = usb_serial_generic_open(tty, port);
if (r)
goto err_kill_interrupt_urb;
@@ -593,6 +584,12 @@ static int ch341_reset_resume(struct usb
ret);
return ret;
}
+
+ ret = ch341_get_status(port->serial->dev, priv);
+ if (ret < 0) {
+ dev_err(&port->dev, "failed to read modem status: %d\n",
+ ret);
+ }
}
return usb_serial_generic_resume(serial);