commit 02303f73373aa1da19dbec510ec5a4e2576f9610
Author: Dan Williams <dcbw@redhat.com>
Date:   Fri Nov 19 16:04:00 2010 -0600

    usb-wwan: implement TIOCGSERIAL and TIOCSSERIAL to avoid blocking close(2)
    
    Some devices (ex ZTE 2726) simply don't respond at all when data is sent
    to some of their USB interfaces.  The data gets stuck in the TTYs queue
    and sits there until close(2), which them blocks because closing_wait
    defaults to 30 seconds (even though the fd is O_NONBLOCK).  This is
    rarely desired.  Implement the standard mechanism to adjust closing_wait
    and let applications handle it how they want to.
    
    Signed-off-by: Dan Williams <dcbw@redhat.com>

diff --git a/drivers/usb/serial/option.c b/drivers/usb/serial/option.c
index 2297fb1..2a56cc3 100644
--- a/drivers/usb/serial/option.c
+++ b/drivers/usb/serial/option.c
@@ -989,6 +989,7 @@ static struct usb_serial_driver option_1port_device = {
 	.set_termios       = usb_wwan_set_termios,
 	.tiocmget          = usb_wwan_tiocmget,
 	.tiocmset          = usb_wwan_tiocmset,
+	.ioctl             = usb_wwan_ioctl,
 	.attach            = usb_wwan_startup,
 	.disconnect        = usb_wwan_disconnect,
 	.release           = usb_wwan_release,
diff --git a/drivers/usb/serial/usb-wwan.h b/drivers/usb/serial/usb-wwan.h
index 2be298a..3ab77c5 100644
--- a/drivers/usb/serial/usb-wwan.h
+++ b/drivers/usb/serial/usb-wwan.h
@@ -18,6 +18,8 @@ extern void usb_wwan_set_termios(struct tty_struct *tty,
 extern int usb_wwan_tiocmget(struct tty_struct *tty, struct file *file);
 extern int usb_wwan_tiocmset(struct tty_struct *tty, struct file *file,
 			     unsigned int set, unsigned int clear);
+extern int usb_wwan_ioctl(struct tty_struct *tty, struct file *file,
+			  unsigned int cmd, unsigned long arg);
 extern int usb_wwan_send_setup(struct usb_serial_port *port);
 extern int usb_wwan_write(struct tty_struct *tty, struct usb_serial_port *port,
 			  const unsigned char *buf, int count);
diff --git a/drivers/usb/serial/usb_wwan.c b/drivers/usb/serial/usb_wwan.c
index fbc9467..660b7ca 100644
--- a/drivers/usb/serial/usb_wwan.c
+++ b/drivers/usb/serial/usb_wwan.c
@@ -33,6 +33,7 @@
 #include <linux/bitops.h>
 #include <linux/usb.h>
 #include <linux/usb/serial.h>
+#include <linux/serial.h>
 #include "usb-wwan.h"
 
 static int debug;
@@ -123,6 +124,83 @@ int usb_wwan_tiocmset(struct tty_struct *tty, struct file *file,
 }
 EXPORT_SYMBOL(usb_wwan_tiocmset);
 
+static int get_serial_info(struct usb_serial_port *port,
+			   struct serial_struct __user *retinfo)
+{
+	struct serial_struct tmp;
+
+	if (!retinfo)
+		return -EFAULT;
+
+	memset(&tmp, 0, sizeof(tmp));
+	tmp.line            = port->serial->minor;
+	tmp.port            = port->number;
+	tmp.baud_base       = tty_get_baud_rate(port->port.tty);
+	tmp.close_delay	    = port->port.close_delay / 10;
+	tmp.closing_wait    = port->port.closing_wait == ASYNC_CLOSING_WAIT_NONE ?
+				 ASYNC_CLOSING_WAIT_NONE :
+				 port->port.closing_wait / 10;
+
+	if (copy_to_user(retinfo, &tmp, sizeof(*retinfo)))
+		return -EFAULT;
+	return 0;
+}
+
+static int set_serial_info(struct usb_serial_port *port,
+			   struct serial_struct __user *newinfo)
+{
+	struct serial_struct new_serial;
+	unsigned int closing_wait, close_delay;
+	int retval = 0;
+
+	if (copy_from_user(&new_serial, newinfo, sizeof(new_serial)))
+		return -EFAULT;
+
+	close_delay = new_serial.close_delay * 10;
+	closing_wait = new_serial.closing_wait == ASYNC_CLOSING_WAIT_NONE ?
+			ASYNC_CLOSING_WAIT_NONE : new_serial.closing_wait * 10;
+
+	mutex_lock(&port->port.mutex);
+
+	if (!capable(CAP_SYS_ADMIN)) {
+		if ((close_delay != port->port.close_delay) ||
+		    (closing_wait != port->port.closing_wait))
+			retval = -EPERM;
+		else
+			retval = -EOPNOTSUPP;
+	} else {
+		port->port.close_delay  = close_delay;
+		port->port.closing_wait = closing_wait;
+	}
+
+	mutex_unlock(&port->port.mutex);
+	return retval;
+}
+
+int usb_wwan_ioctl(struct tty_struct *tty, struct file *file,
+		   unsigned int cmd, unsigned long arg)
+{
+	struct usb_serial_port *port = tty->driver_data;
+
+	dbg("%s cmd 0x%04x", __func__, cmd);
+
+	switch (cmd) {
+	case TIOCGSERIAL:
+		return get_serial_info(port,
+				       (struct serial_struct __user *) arg);
+	case TIOCSSERIAL:
+		return set_serial_info(port,
+				       (struct serial_struct __user *) arg);
+	default:
+		break;
+	}
+
+	dbg("%s arg not supported", __func__);
+
+	return -ENOIOCTLCMD;
+}
+EXPORT_SYMBOL(usb_wwan_ioctl);
+
 /* Write */
 int usb_wwan_write(struct tty_struct *tty, struct usb_serial_port *port,
 		   const unsigned char *buf, int count)