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Commit a0467a96 authored by Johan Hovold's avatar Johan Hovold
Browse files

USB: serial: ch341: fix modem-status handling 



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: 664d5df9 ("USB: usb-serial ch341: support for DTR/RTS/CTS")
Signed-off-by: default avatarJohan Hovold <johan@kernel.org>
parent 56e6d907

drivers/usb/serial/ch341.c

+12 −15
Original line number Diff line number Diff line
@@ -248,21 +248,11 @@ static int ch341_configure(struct usb_device *dev, struct ch341_private *priv) 
	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, priv->lcr);

	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;
@@ -334,14 +324,9 @@ static void ch341_close(struct usb_serial_port *port) 
/* 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);
@@ -353,6 +338,12 @@ static int ch341_open(struct tty_struct *tty, struct usb_serial_port *port) 
		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;
@@ -619,6 +610,12 @@ static int ch341_reset_resume(struct usb_serial *serial) 
				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);