37 files changed, 313 insertions, 208 deletions

diff --git a/drivers/char/tty_port.c b/drivers/char/tty_port.c
index 6fadb19d630b..553b0e9d8d17 100644
--- a/drivers/char/tty_port.c
+++ b/drivers/char/tty_port.c
@@ -23,6 +23,7 @@ void tty_port_init(struct tty_port *port)
         init_waitqueue_head(&port->open_wait);
         init_waitqueue_head(&port->close_wait);
         mutex_init(&port->mutex);
+        spin_lock_init(&port->lock);
         port->close_delay = (50 * HZ) / 100;
         port->closing_wait = (3000 * HZ) / 100;
 }
@@ -53,3 +54,43 @@ void tty_port_free_xmit_buf(struct tty_port *port)
 EXPORT_SYMBOL(tty_port_free_xmit_buf);
 
 
+/**
+ *      tty_port_tty_get        -       get a tty reference
+ *      @port: tty port
+ *
+ *      Return a refcount protected tty instance or NULL if the port is not
+ *      associated with a tty (eg due to close or hangup)
+ */
+
+struct tty_struct *tty_port_tty_get(struct tty_port *port)
+{
+        unsigned long flags;
+        struct tty_struct *tty;
+
+        spin_lock_irqsave(&port->lock, flags);
+        tty = tty_kref_get(port->tty);
+        spin_unlock_irqrestore(&port->lock, flags);
+        return tty;
+}
+EXPORT_SYMBOL(tty_port_tty_get);
+
+/**
+ *      tty_port_tty_set        -       set the tty of a port
+ *      @port: tty port
+ *      @tty: the tty
+ *
+ *      Associate the port and tty pair. Manages any internal refcounts.
+ *      Pass NULL to deassociate a port
+ */
+
+void tty_port_tty_set(struct tty_port *port, struct tty_struct *tty)
+{
+        unsigned long flags;
+
+        spin_lock_irqsave(&port->lock, flags);
+        if (port->tty)
+                tty_kref_put(port->tty);
+        port->tty = tty;
+        spin_unlock_irqrestore(&port->lock, flags);
+}
+EXPORT_SYMBOL(tty_port_tty_set);
diff --git a/drivers/usb/serial/aircable.c b/drivers/usb/serial/aircable.c
index 79ea98c66fa8..99fb7dc59c45 100644
--- a/drivers/usb/serial/aircable.c
+++ b/drivers/usb/serial/aircable.c
@@ -272,7 +272,7 @@ static void aircable_read(struct work_struct *work)
          * 64 bytes, to ensure I do not get throttled.
          * Ask USB mailing list for better aproach.
          */
-        tty = port->port.tty;
+        tty = tty_port_tty_get(&port->port);
 
         if (!tty) {
                 schedule_work(&priv->rx_work);
@@ -283,12 +283,13 @@ static void aircable_read(struct work_struct *work)
         count = min(64, serial_buf_data_avail(priv->rx_buf));
 
         if (count <= 0)
-                return; /* We have finished sending everything. */
+                goto out; /* We have finished sending everything. */
 
         tty_prepare_flip_string(tty, &data, count);
         if (!data) {
-                err("%s- kzalloc(%d) failed.", __func__, count);
-                return;
+                dev_err(&port->dev, "%s- kzalloc(%d) failed.",
+                                                        __func__, count);
+                goto out;
         }
 
         serial_buf_get(priv->rx_buf, data, count);
@@ -297,7 +298,8 @@ static void aircable_read(struct work_struct *work)
 
         if (serial_buf_data_avail(priv->rx_buf))
                 schedule_work(&priv->rx_work);
-
+out:            
+        tty_kref_put(tty);
         return;
 }
 /* End of private methods */
@@ -495,7 +497,7 @@ static void aircable_read_bulk_callback(struct urb *urb)
         usb_serial_debug_data(debug, &port->dev, __func__,
                                 urb->actual_length, urb->transfer_buffer);
 
-        tty = port->port.tty;
+        tty = tty_port_tty_get(&port->port);
         if (tty && urb->actual_length) {
                 if (urb->actual_length <= 2) {
                         /* This is an incomplete package */
@@ -527,6 +529,7 @@ static void aircable_read_bulk_callback(struct urb *urb)
                 }
                 aircable_read(&priv->rx_work);
         }
+        tty_kref_put(tty);
 
         /* Schedule the next read _if_ we are still open */
         if (port->port.count) {
diff --git a/drivers/usb/serial/belkin_sa.c b/drivers/usb/serial/belkin_sa.c
index 2ebe06c3405a..1913bc7c5f0b 100644
--- a/drivers/usb/serial/belkin_sa.c
+++ b/drivers/usb/serial/belkin_sa.c
@@ -322,7 +322,7 @@ static void belkin_sa_read_int_callback(struct urb *urb)
          * to look in to this before committing any code.
          */
         if (priv->last_lsr & BELKIN_SA_LSR_ERR) {
-                tty = port->port.tty;
+                tty = tty_port_tty_get(&port->port);
                 /* Overrun Error */
                 if (priv->last_lsr & BELKIN_SA_LSR_OE) {
                 }
@@ -335,6 +335,7 @@ static void belkin_sa_read_int_callback(struct urb *urb)
                 /* Break Indicator */
                 if (priv->last_lsr & BELKIN_SA_LSR_BI) {
                 }
+                tty_kref_put(tty);
         }
 #endif
         spin_unlock_irqrestore(&priv->lock, flags);
diff --git a/drivers/usb/serial/console.c b/drivers/usb/serial/console.c
index e980766bb84b..5b20de130e08 100644
--- a/drivers/usb/serial/console.c
+++ b/drivers/usb/serial/console.c
@@ -117,7 +117,7 @@ static int usb_console_setup(struct console *co, char *options)
         }
 
         port = serial->port[0];
-        port->port.tty = NULL;
+        tty_port_tty_set(&port->port, NULL);
 
         info->port = port;
 
@@ -143,7 +143,7 @@ static int usb_console_setup(struct console *co, char *options)
                         }
                         memset(&dummy, 0, sizeof(struct ktermios));
                         tty->termios = termios;
-                        port->port.tty = tty;
+                        tty_port_tty_set(&port->port, tty);
                 }
 
                 /* only call the device specific open if this
@@ -163,7 +163,7 @@ static int usb_console_setup(struct console *co, char *options)
                         tty_termios_encode_baud_rate(termios, baud, baud);
                         serial->type->set_termios(tty, port, &dummy);
 
-                        port->port.tty = NULL;
+                        tty_port_tty_set(&port->port, NULL);
                         kfree(termios);
                         kfree(tty);
                 }
@@ -176,7 +176,7 @@ out:
         return retval;
 free_termios:
         kfree(termios);
-        port->port.tty = NULL;
+        tty_port_tty_set(&port->port, NULL);
 free_tty:
         kfree(tty);
 reset_open_count:
diff --git a/drivers/usb/serial/cyberjack.c b/drivers/usb/serial/cyberjack.c
index b4d72351cb96..94ef36c4764b 100644
--- a/drivers/usb/serial/cyberjack.c
+++ b/drivers/usb/serial/cyberjack.c
@@ -384,7 +384,7 @@ static void cyberjack_read_bulk_callback(struct urb *urb)
                 return;
         }
 
-        tty = port->port.tty;
+        tty = tty_port_tty_get(&port->port);
         if (!tty) {
                 dbg("%s - ignoring since device not open\n", __func__);
                 return;
@@ -394,6 +394,7 @@ static void cyberjack_read_bulk_callback(struct urb *urb)
                 tty_insert_flip_string(tty, data, urb->actual_length);
                 tty_flip_buffer_push(tty);
         }
+        tty_kref_put(tty);
 
         spin_lock(&priv->lock);
 
diff --git a/drivers/usb/serial/cypress_m8.c b/drivers/usb/serial/cypress_m8.c
index 22837a3f2f89..f3514a91f915 100644
--- a/drivers/usb/serial/cypress_m8.c
+++ b/drivers/usb/serial/cypress_m8.c
@@ -1286,7 +1286,7 @@ static void cypress_read_int_callback(struct urb *urb)
         }
         spin_unlock_irqrestore(&priv->lock, flags);
 
-        tty = port->port.tty;
+        tty = tty_port_tty_get(&port->port);
         if (!tty) {
                 dbg("%s - bad tty pointer - exiting", __func__);
                 return;
@@ -1362,7 +1362,7 @@ static void cypress_read_int_callback(struct urb *urb)
                                         data[i]);
                         tty_insert_flip_char(tty, data[i], tty_flag);
                 }
-                tty_flip_buffer_push(port->port.tty);
+                tty_flip_buffer_push(tty);
         }
 
         spin_lock_irqsave(&priv->lock, flags);
@@ -1371,6 +1371,7 @@ static void cypress_read_int_callback(struct urb *urb)
         spin_unlock_irqrestore(&priv->lock, flags);
 
 continue_read:
+        tty_kref_put(tty);
 
         /* Continue trying to always read... unless the port has closed. */
 
diff --git a/drivers/usb/serial/digi_acceleport.c b/drivers/usb/serial/digi_acceleport.c
index 240aad1acaab..5756ac6d6c92 100644
--- a/drivers/usb/serial/digi_acceleport.c
+++ b/drivers/usb/serial/digi_acceleport.c
@@ -604,7 +604,9 @@ static void digi_wakeup_write_lock(struct work_struct *work)
 
 static void digi_wakeup_write(struct usb_serial_port *port)
 {
-        tty_wakeup(port->port.tty);
+        struct tty_struct *tty = tty_port_tty_get(&port->port);
+        tty_wakeup(tty);
+        tty_kref_put(tty);
 }
 
 
@@ -1668,7 +1670,7 @@ static int digi_read_inb_callback(struct urb *urb)
 {
 
         struct usb_serial_port *port = urb->context;
-        struct tty_struct *tty = port->port.tty;
+        struct tty_struct *tty;
         struct digi_port *priv = usb_get_serial_port_data(port);
         int opcode = ((unsigned char *)urb->transfer_buffer)[0];
         int len = ((unsigned char *)urb->transfer_buffer)[1];
@@ -1692,6 +1694,7 @@ static int digi_read_inb_callback(struct urb *urb)
                 return -1;
         }
 
+        tty = tty_port_tty_get(&port->port);
         spin_lock(&priv->dp_port_lock);
 
         /* check for throttle; if set, do not resubmit read urb */
@@ -1735,6 +1738,7 @@ static int digi_read_inb_callback(struct urb *urb)
                 }
         }
         spin_unlock(&priv->dp_port_lock);
+        tty_kref_put(tty);
 
         if (opcode == DIGI_CMD_RECEIVE_DISABLE)
                 dbg("%s: got RECEIVE_DISABLE", __func__);
@@ -1760,6 +1764,7 @@ static int digi_read_oob_callback(struct urb *urb)
 
         struct usb_serial_port *port = urb->context;
         struct usb_serial *serial = port->serial;
+        struct tty_struct *tty;
         struct digi_port *priv = usb_get_serial_port_data(port);
         int opcode, line, status, val;
         int i;
@@ -1787,10 +1792,11 @@ static int digi_read_oob_callback(struct urb *urb)
                 if (priv == NULL)
                         return -1;
 
+                tty = tty_port_tty_get(&port->port);
                 rts = 0;
                 if (port->port.count)
-                        rts = port->port.tty->termios->c_cflag & CRTSCTS;
-
+                        rts = tty->termios->c_cflag & CRTSCTS;
+                
                 if (opcode == DIGI_CMD_READ_INPUT_SIGNALS) {
                         spin_lock(&priv->dp_port_lock);
                         /* convert from digi flags to termiox flags */
@@ -1798,14 +1804,14 @@ static int digi_read_oob_callback(struct urb *urb)
                                 priv->dp_modem_signals |= TIOCM_CTS;
                                 /* port must be open to use tty struct */
                                 if (rts) {
-                                        port->port.tty->hw_stopped = 0;
+                                        tty->hw_stopped = 0;
                                         digi_wakeup_write(port);
                                 }
                         } else {
                                 priv->dp_modem_signals &= ~TIOCM_CTS;
                                 /* port must be open to use tty struct */
                                 if (rts)
-                                        port->port.tty->hw_stopped = 1;
+                                        tty->hw_stopped = 1;
                         }
                         if (val & DIGI_READ_INPUT_SIGNALS_DSR)
                                 priv->dp_modem_signals |= TIOCM_DSR;
@@ -1830,6 +1836,7 @@ static int digi_read_oob_callback(struct urb *urb)
                 } else if (opcode == DIGI_CMD_IFLUSH_FIFO) {
                         wake_up_interruptible(&priv->dp_flush_wait);
                 }
+                tty_kref_put(tty);
         }
         return 0;
 
diff --git a/drivers/usb/serial/empeg.c b/drivers/usb/serial/empeg.c
index a6ab5b58d9ca..1072e847280f 100644
--- a/drivers/usb/serial/empeg.c
+++ b/drivers/usb/serial/empeg.c
@@ -33,9 +33,8 @@
  *      Moved MOD_DEC_USE_COUNT to end of empeg_close().
  *
  * (12/03/2000) gb
- *      Added port->port.tty->ldisc.set_termios(port->port.tty, NULL) to
- *      empeg_open(). This notifies the tty driver that the termios have
- *      changed.
+ *      Added tty->ldisc.set_termios(port, tty, NULL) to empeg_open().
+ *      This notifies the tty driver that the termios have changed.
  *
  * (11/13/2000) gb
  *      Moved tty->low_latency = 1 from empeg_read_bulk_callback() to
@@ -354,7 +353,7 @@ static void empeg_read_bulk_callback(struct urb *urb)
 
         usb_serial_debug_data(debug, &port->dev, __func__,
                                                 urb->actual_length, data);
-        tty = port->port.tty;
+        tty = tty_port_tty_get(&port->port);
 
         if (urb->actual_length) {
                 tty_buffer_request_room(tty, urb->actual_length);
@@ -362,6 +361,7 @@ static void empeg_read_bulk_callback(struct urb *urb)
                 tty_flip_buffer_push(tty);
                 bytes_in += urb->actual_length;
         }
+        tty_kref_put(tty);
 
         /* Continue trying to always read  */
         usb_fill_bulk_urb(
diff --git a/drivers/usb/serial/ftdi_sio.c b/drivers/usb/serial/ftdi_sio.c
index 1ac7e802b4b6..c2ac129557aa 100644
--- a/drivers/usb/serial/ftdi_sio.c
+++ b/drivers/usb/serial/ftdi_sio.c
@@ -1808,7 +1808,7 @@ static void ftdi_read_bulk_callback(struct urb *urb)
         if (port->port.count <= 0)
                 return;
 
-        tty = port->port.tty;
+        tty = tty_port_tty_get(&port->port);
         if (!tty) {
                 dbg("%s - bad tty pointer - exiting", __func__);
                 return;
@@ -1817,7 +1817,7 @@ static void ftdi_read_bulk_callback(struct urb *urb)
         priv = usb_get_serial_port_data(port);
         if (!priv) {
                 dbg("%s - bad port private data pointer - exiting", __func__);
-                return;
+                goto out;
         }
 
         if (urb != port->read_urb)
@@ -1827,7 +1827,7 @@ static void ftdi_read_bulk_callback(struct urb *urb)
                 /* This will happen at close every time so it is a dbg not an
                    err */
                 dbg("(this is ok on close) nonzero read bulk status received: %d", status);
-                return;
+                goto out;
         }
 
         /* count data bytes, but not status bytes */
@@ -1838,7 +1838,8 @@ static void ftdi_read_bulk_callback(struct urb *urb)
         spin_unlock_irqrestore(&priv->rx_lock, flags);
 
         ftdi_process_read(&priv->rx_work.work);
-
+out:
+        tty_kref_put(tty);
 } /* ftdi_read_bulk_callback */
 
 
@@ -1863,7 +1864,7 @@ static void ftdi_process_read(struct work_struct *work)
         if (port->port.count <= 0)
                 return;
 
-        tty = port->port.tty;
+        tty = tty_port_tty_get(&port->port);
         if (!tty) {
                 dbg("%s - bad tty pointer - exiting", __func__);
                 return;
@@ -1872,13 +1873,13 @@ static void ftdi_process_read(struct work_struct *work)
         priv = usb_get_serial_port_data(port);
         if (!priv) {
                 dbg("%s - bad port private data pointer - exiting", __func__);
-                return;
+                goto out;
         }
 
         urb = port->read_urb;
         if (!urb) {
                 dbg("%s - bad read_urb pointer - exiting", __func__);
-                return;
+                goto out;
         }
 
         data = urb->transfer_buffer;
@@ -2020,7 +2021,7 @@ static void ftdi_process_read(struct work_struct *work)
                         schedule_delayed_work(&priv->rx_work, 1);
                 else
                         dbg("%s - port is closed", __func__);
-                return;
+                goto out;
         }
 
         /* urb is completely processed */
@@ -2041,6 +2042,8 @@ static void ftdi_process_read(struct work_struct *work)
                         err("%s - failed resubmitting read urb, error %d",
                                                         __func__, result);
         }
+out:
+        tty_kref_put(tty);
 } /* ftdi_process_read */
 
 
diff --git a/drivers/usb/serial/garmin_gps.c b/drivers/usb/serial/garmin_gps.c
index d95382088075..2ad0569bcf19 100644
--- a/drivers/usb/serial/garmin_gps.c
+++ b/drivers/usb/serial/garmin_gps.c
@@ -276,7 +276,7 @@ static inline int isAbortTrfCmnd(const unsigned char *buf)
 static void send_to_tty(struct usb_serial_port *port,
                         char *data, unsigned int actual_length)
 {
-        struct tty_struct *tty = port->port.tty;
+        struct tty_struct *tty = tty_port_tty_get(&port->port);
 
         if (tty && actual_length) {
 
@@ -287,6 +287,7 @@ static void send_to_tty(struct usb_serial_port *port,
                 tty_insert_flip_string(tty, data, actual_length);
                 tty_flip_buffer_push(tty);
         }
+        tty_kref_put(tty);
 }
 
 
diff --git a/drivers/usb/serial/generic.c b/drivers/usb/serial/generic.c
index fe84c88ec20c..814909f1ee63 100644
--- a/drivers/usb/serial/generic.c
+++ b/drivers/usb/serial/generic.c
@@ -330,7 +330,7 @@ static void resubmit_read_urb(struct usb_serial_port *port, gfp_t mem_flags)
 static void flush_and_resubmit_read_urb(struct usb_serial_port *port)
 {
         struct urb *urb = port->read_urb;
-        struct tty_struct *tty = port->port.tty;
+        struct tty_struct *tty = tty_port_tty_get(&port->port);
         int room;
 
         /* Push data to tty */
@@ -341,6 +341,7 @@ static void flush_and_resubmit_read_urb(struct usb_serial_port *port)
                         tty_flip_buffer_push(tty);
                 }
         }
+        tty_kref_put(tty);
 
         resubmit_read_urb(port, GFP_ATOMIC);
 }
diff --git a/drivers/usb/serial/io_edgeport.c b/drivers/usb/serial/io_edgeport.c
index bfa508ddb0fe..611f97fd62f1 100644
--- a/drivers/usb/serial/io_edgeport.c
+++ b/drivers/usb/serial/io_edgeport.c
@@ -600,6 +600,7 @@ static void edge_interrupt_callback(struct urb *urb)
         struct edgeport_serial  *edge_serial = urb->context;
         struct edgeport_port *edge_port;
         struct usb_serial_port *port;
+        struct tty_struct *tty;
         unsigned char *data = urb->transfer_buffer;
         int length = urb->actual_length;
         int bytes_avail;
@@ -675,9 +676,12 @@ static void edge_interrupt_callback(struct urb *urb)
 
                                         /* tell the tty driver that something
                                            has changed */
-                                        if (edge_port->port->port.tty)
-                                                tty_wakeup(edge_port->port->port.tty);
-
+                                        tty = tty_port_tty_get(
+                                                &edge_port->port->port);
+                                        if (tty) {
+                                                tty_wakeup(tty);
+                                                tty_kref_put(tty);
+                                        }
                                         /* Since we have more credit, check
                                            if more data can be sent */
                                         send_more_port_data(edge_serial,
@@ -778,13 +782,14 @@ static void edge_bulk_out_data_callback(struct urb *urb)
                     __func__, status);
         }
 
-        tty = edge_port->port->port.tty;
+        tty = tty_port_tty_get(&edge_port->port->port);
 
         if (tty && edge_port->open) {
                 /* let the tty driver wakeup if it has a special
                    write_wakeup function */
                 tty_wakeup(tty);
         }
+        tty_kref_put(tty);
 
         /* Release the Write URB */
         edge_port->write_in_progress = false;
@@ -826,11 +831,12 @@ static void edge_bulk_out_cmd_callback(struct urb *urb)
         }
 
         /* Get pointer to tty */
-        tty = edge_port->port->port.tty;
+        tty = tty_port_tty_get(&edge_port->port->port);
 
         /* tell the tty driver that something has changed */
         if (tty && edge_port->open)
                 tty_wakeup(tty);
+        tty_kref_put(tty);
 
         /* we have completed the command */
         edge_port->commandPending = false;
@@ -1932,11 +1938,13 @@ static void process_rcvd_data(struct edgeport_serial *edge_serial,
                                                         edge_serial->rxPort];
                                 edge_port = usb_get_serial_port_data(port);
                                 if (edge_port->open) {
-                                        tty = edge_port->port->port.tty;
+                                        tty = tty_port_tty_get(
+                                                &edge_port->port->port);
                                         if (tty) {
                                                 dbg("%s - Sending %d bytes to TTY for port %d",
                                                         __func__, rxLen, edge_serial->rxPort);
                                                 edge_tty_recv(&edge_serial->serial->dev->dev, tty, buffer, rxLen);
+                                                tty_kref_put(tty);
                                         }
                                         edge_port->icount.rx += rxLen;
                                 }
@@ -1971,6 +1979,7 @@ static void process_rcvd_status(struct edgeport_serial *edge_serial,
 {
         struct usb_serial_port *port;
         struct edgeport_port *edge_port;
+        struct tty_struct *tty;
         __u8 code = edge_serial->rxStatusCode;
 
         /* switch the port pointer to the one being currently talked about */
@@ -2020,10 +2029,12 @@ static void process_rcvd_status(struct edgeport_serial *edge_serial,
 
                 /* send the current line settings to the port so we are
                    in sync with any further termios calls */
-                /* FIXME: locking on tty */
-                if (edge_port->port->port.tty)
-                        change_port_settings(edge_port->port->port.tty,
-                                edge_port, edge_port->port->port.tty->termios);
+                tty = tty_port_tty_get(&edge_port->port->port);
+                if (tty) {
+                        change_port_settings(tty,
+                                edge_port, tty->termios);
+                        tty_kref_put(tty);
+                }
 
                 /* we have completed the open */
                 edge_port->openPending = false;
@@ -2163,10 +2174,14 @@ static void handle_new_lsr(struct edgeport_port *edge_port, __u8 lsrData,
         }
 
         /* Place LSR data byte into Rx buffer */
-        if (lsrData && edge_port->port->port.tty)
-                edge_tty_recv(&edge_port->port->dev,
-                                        edge_port->port->port.tty, &data, 1);
-
+        if (lsrData) {
+                struct tty_struct *tty =
+                                tty_port_tty_get(&edge_port->port->port);
+                if (tty) {
+                        edge_tty_recv(&edge_port->port->dev, tty, &data, 1);
+                        tty_kref_put(tty);
+                }
+        }
         /* update input line counters */
         icount = &edge_port->icount;
         if (newLsr & LSR_BREAK)
diff --git a/drivers/usb/serial/io_ti.c b/drivers/usb/serial/io_ti.c
index cb4c54316cf5..541dd8e6e7a2 100644
--- a/drivers/usb/serial/io_ti.c
+++ b/drivers/usb/serial/io_ti.c
@@ -572,7 +572,7 @@ static void chase_port(struct edgeport_port *port, unsigned long timeout,
                                                                 int flush)
 {
         int baud_rate;
-        struct tty_struct *tty = port->port->port.tty;
+        struct tty_struct *tty = tty_port_tty_get(&port->port->port);
         wait_queue_t wait;
         unsigned long flags;
 
@@ -599,6 +599,7 @@ static void chase_port(struct edgeport_port *port, unsigned long timeout,
         if (flush)
                 edge_buf_clear(port->ep_out_buf);
         spin_unlock_irqrestore(&port->ep_lock, flags);
+        tty_kref_put(tty);
 
         /* wait for data to drain from the device */
         timeout += jiffies;
@@ -1554,7 +1555,7 @@ static void handle_new_msr(struct edgeport_port *edge_port, __u8 msr)
         /* Save the new modem status */
         edge_port->shadow_msr = msr & 0xf0;
 
-        tty = edge_port->port->port.tty;
+        tty = tty_port_tty_get(&edge_port->port->port);
         /* handle CTS flow control */
         if (tty && C_CRTSCTS(tty)) {
                 if (msr & EDGEPORT_MSR_CTS) {
@@ -1564,6 +1565,7 @@ static void handle_new_msr(struct edgeport_port *edge_port, __u8 msr)
                         tty->hw_stopped = 1;
                 }
         }
+        tty_kref_put(tty);
 
         return;
 }
@@ -1574,6 +1576,7 @@ static void handle_new_lsr(struct edgeport_port *edge_port, int lsr_data,
         struct async_icount *icount;
         __u8 new_lsr = (__u8)(lsr & (__u8)(LSR_OVER_ERR | LSR_PAR_ERR |
                                                 LSR_FRM_ERR | LSR_BREAK));
+        struct tty_struct *tty;
 
         dbg("%s - %02x", __func__, new_lsr);
 
@@ -1587,8 +1590,13 @@ static void handle_new_lsr(struct edgeport_port *edge_port, int lsr_data,
                 new_lsr &= (__u8)(LSR_OVER_ERR | LSR_BREAK);
 
         /* Place LSR data byte into Rx buffer */
-        if (lsr_data && edge_port->port->port.tty)
-                edge_tty_recv(&edge_port->port->dev, edge_port->port->port.tty, &data, 1);
+        if (lsr_data) {
+                tty = tty_port_tty_get(&edge_port->port->port);
+                if (tty) {
+                        edge_tty_recv(&edge_port->port->dev, tty, &data, 1);
+                        tty_kref_put(tty);
+                }
+        }
 
         /* update input line counters */
         icount = &edge_port->icount;
@@ -1749,7 +1757,7 @@ static void edge_bulk_in_callback(struct urb *urb)
                 ++data;
         }
 
-        tty = edge_port->port->port.tty;
+        tty = tty_port_tty_get(&edge_port->port->port);
         if (tty && urb->actual_length) {
                 usb_serial_debug_data(debug, &edge_port->port->dev,
                                         __func__, urb->actual_length, data);
@@ -1761,6 +1769,7 @@ static void edge_bulk_in_callback(struct urb *urb)
                                                         urb->actual_length);
                 edge_port->icount.rx += urb->actual_length;
         }
+        tty_kref_put(tty);
 
 exit:
         /* continue read unless stopped */
@@ -1796,6 +1805,7 @@ static void edge_bulk_out_callback(struct urb *urb)
         struct usb_serial_port *port = urb->context;
         struct edgeport_port *edge_port = usb_get_serial_port_data(port);
         int status = urb->status;
+        struct tty_struct *tty;
 
         dbg("%s - port %d", __func__, port->number);
 
@@ -1818,7 +1828,9 @@ static void edge_bulk_out_callback(struct urb *urb)
         }
 
         /* send any buffered data */
-        edge_send(port->port.tty);
+        tty = tty_port_tty_get(&port->port);
+        edge_send(tty);
+        tty_kref_put(tty);
 }
 
 static int edge_open(struct tty_struct *tty,
@@ -1876,7 +1888,7 @@ static int edge_open(struct tty_struct *tty,
 
         /* set up the port settings */
         if (tty)
-                edge_set_termios(tty, port, port->port.tty->termios);
+                edge_set_termios(tty, port, tty->termios);
 
         /* open up the port */
 
diff --git a/drivers/usb/serial/ipaq.c b/drivers/usb/serial/ipaq.c
index cd9a2e138c8b..2affa9c118b2 100644
--- a/drivers/usb/serial/ipaq.c
+++ b/drivers/usb/serial/ipaq.c
@@ -764,13 +764,14 @@ static void ipaq_read_bulk_callback(struct urb *urb)
         usb_serial_debug_data(debug, &port->dev, __func__,
                                                 urb->actual_length, data);
 
-        tty = port->port.tty;
+        tty = tty_port_tty_get(&port->port);
         if (tty && urb->actual_length) {
                 tty_buffer_request_room(tty, urb->actual_length);
                 tty_insert_flip_string(tty, data, urb->actual_length);
                 tty_flip_buffer_push(tty);
                 bytes_in += urb->actual_length;
         }
+        tty_kref_put(tty);
 
         /* Continue trying to always read  */
         usb_fill_bulk_urb(port->read_urb, port->serial->dev,
diff --git a/drivers/usb/serial/ipw.c b/drivers/usb/serial/ipw.c
index a842025b9b57..480cac27d646 100644
--- a/drivers/usb/serial/ipw.c
+++ b/drivers/usb/serial/ipw.c
@@ -170,12 +170,13 @@ static void ipw_read_bulk_callback(struct urb *urb)
         usb_serial_debug_data(debug, &port->dev, __func__,
                                         urb->actual_length, data);
 
-        tty = port->port.tty;
+        tty = tty_port_tty_get(&port->port);
         if (tty && urb->actual_length) {
                 tty_buffer_request_room(tty, urb->actual_length);
                 tty_insert_flip_string(tty, data, urb->actual_length);
                 tty_flip_buffer_push(tty);
         }
+        tty_kref_put(tty);
 
         /* Continue trying to always read  */
         usb_fill_bulk_urb(port->read_urb, port->serial->dev,
diff --git a/drivers/usb/serial/ir-usb.c b/drivers/usb/serial/ir-usb.c
index e59155c6607d..45d4043e04ab 100644
--- a/drivers/usb/serial/ir-usb.c
+++ b/drivers/usb/serial/ir-usb.c
@@ -465,11 +465,12 @@ static void ir_read_bulk_callback(struct urb *urb)
                         ir_baud = *data & 0x0f;
                 usb_serial_debug_data(debug, &port->dev, __func__,
                                                 urb->actual_length, data);
-                tty = port->port.tty;
+                tty = tty_port_tty_get(&port->port);
                 if (tty_buffer_request_room(tty, urb->actual_length - 1)) {
                         tty_insert_flip_string(tty, data+1, urb->actual_length - 1);
                         tty_flip_buffer_push(tty);
                 }
+                tty_kref_put(tty);
 
                 /*
                  * No break here.
diff --git a/drivers/usb/serial/iuu_phoenix.c b/drivers/usb/serial/iuu_phoenix.c
index ddff37fa6339..53710aa7eadd 100644
--- a/drivers/usb/serial/iuu_phoenix.c
+++ b/drivers/usb/serial/iuu_phoenix.c
@@ -629,13 +629,14 @@ static void read_buf_callback(struct urb *urb)
         }
 
         dbg("%s - %i chars to write", __func__, urb->actual_length);
-        tty = port->port.tty;
+        tty = tty_port_tty_get(&port->port);
         if (data == NULL)
                 dbg("%s - data is NULL !!!", __func__);
         if (tty && urb->actual_length && data) {
                 tty_insert_flip_string(tty, data, urb->actual_length);
                 tty_flip_buffer_push(tty);
         }
+        tty_kref_put(tty);
         iuu_led_activity_on(urb);
 }
 
diff --git a/drivers/usb/serial/keyspan.c b/drivers/usb/serial/keyspan.c
index 704716f6f6d3..15447af48691 100644
--- a/drivers/usb/serial/keyspan.c
+++ b/drivers/usb/serial/keyspan.c
@@ -430,7 +430,7 @@ static void	usa26_indat_callback(struct urb *urb)
         }
 
         port =  urb->context;
-        tty = port->port.tty;
+        tty = tty_port_tty_get(&port->port);
         if (tty && urb->actual_length) {
                 /* 0x80 bit is error flag */
                 if ((data[0] & 0x80) == 0) {
@@ -459,6 +459,7 @@ static void	usa26_indat_callback(struct urb *urb)
                 }
                 tty_flip_buffer_push(tty);
         }
+        tty_kref_put(tty);
 
         /* Resubmit urb so we continue receiving */
         urb->dev = port->serial->dev;
@@ -513,6 +514,7 @@ static void	usa26_instat_callback(struct urb *urb)
         struct usb_serial                       *serial;
         struct usb_serial_port                  *port;
         struct keyspan_port_private             *p_priv;
+        struct tty_struct                       *tty;
         int old_dcd_state, err;
         int status = urb->status;
 
@@ -553,12 +555,11 @@ static void	usa26_instat_callback(struct urb *urb)
         p_priv->dcd_state = ((msg->gpia_dcd) ? 1 : 0);
         p_priv->ri_state = ((msg->ri) ? 1 : 0);
 
-        if (port->port.tty && !C_CLOCAL(port->port.tty)
-            && old_dcd_state != p_priv->dcd_state) {
-                if (old_dcd_state)
-                        tty_hangup(port->port.tty);
-                /*  else */
-                /*      wake_up_interruptible(&p_priv->open_wait); */
+        if (old_dcd_state != p_priv->dcd_state) {
+                tty = tty_port_tty_get(&port->port);
+                if (tty && !C_CLOCAL(tty))
+                        tty_hangup(tty);
+                tty_kref_put(tty);
         }
 
         /* Resubmit urb so we continue receiving */
@@ -604,11 +605,12 @@ static void usa28_indat_callback(struct urb *urb)
                 p_priv = usb_get_serial_port_data(port);
                 data = urb->transfer_buffer;
 
-                tty = port->port.tty;
-                if (urb->actual_length) {
+                tty =tty_port_tty_get(&port->port);
+                if (tty && urb->actual_length) {
                         tty_insert_flip_string(tty, data, urb->actual_length);
                         tty_flip_buffer_push(tty);
                 }
+                tty_kref_put(tty);
 
                 /* Resubmit urb so we continue receiving */
                 urb->dev = port->serial->dev;
@@ -652,6 +654,7 @@ static void	usa28_instat_callback(struct urb *urb)
         struct usb_serial                       *serial;
         struct usb_serial_port                  *port;
         struct keyspan_port_private             *p_priv;
+        struct tty_struct                       *tty;
         int old_dcd_state;
         int status = urb->status;
 
@@ -689,12 +692,11 @@ static void	usa28_instat_callback(struct urb *urb)
         p_priv->dcd_state = ((msg->dcd) ? 1 : 0);
         p_priv->ri_state = ((msg->ri) ? 1 : 0);
 
-        if (port->port.tty && !C_CLOCAL(port->port.tty)
-            && old_dcd_state != p_priv->dcd_state) {
-                if (old_dcd_state)
-                        tty_hangup(port->port.tty);
-                /*  else */
-                /*      wake_up_interruptible(&p_priv->open_wait); */
+        if( old_dcd_state != p_priv->dcd_state && old_dcd_state) {
+                tty = tty_port_tty_get(&port->port);
+                if (tty && !C_CLOCAL(tty)) 
+                        tty_hangup(tty);
+                tty_kref_put(tty);
         }
 
                 /* Resubmit urb so we continue receiving */
@@ -785,12 +787,11 @@ static void	usa49_instat_callback(struct urb *urb)
         p_priv->dcd_state = ((msg->dcd) ? 1 : 0);
         p_priv->ri_state = ((msg->ri) ? 1 : 0);
 
-        if (port->port.tty && !C_CLOCAL(port->port.tty)
-            && old_dcd_state != p_priv->dcd_state) {
-                if (old_dcd_state)
-                        tty_hangup(port->port.tty);
-                /*  else */
-                /*      wake_up_interruptible(&p_priv->open_wait); */
+        if (old_dcd_state != p_priv->dcd_state && old_dcd_state) {
+                struct tty_struct *tty = tty_port_tty_get(&port->port);
+                if (tty && !C_CLOCAL(tty))
+                        tty_hangup(tty);
+                tty_kref_put(tty);
         }
 
         /* Resubmit urb so we continue receiving */
@@ -827,7 +828,7 @@ static void	usa49_indat_callback(struct urb *urb)
         }
 
         port =  urb->context;
-        tty = port->port.tty;
+        tty = tty_port_tty_get(&port->port);
         if (tty && urb->actual_length) {
                 /* 0x80 bit is error flag */
                 if ((data[0] & 0x80) == 0) {
@@ -850,6 +851,7 @@ static void	usa49_indat_callback(struct urb *urb)
                 }
                 tty_flip_buffer_push(tty);
         }
+        tty_kref_put(tty);
 
         /* Resubmit urb so we continue receiving */
         urb->dev = port->serial->dev;
@@ -893,7 +895,7 @@ static void usa49wg_indat_callback(struct urb *urb)
                                 return;
                         }
                         port = serial->port[data[i++]];
-                        tty = port->port.tty;
+                        tty = tty_port_tty_get(&port->port);
                         len = data[i++];
 
                         /* 0x80 bit is error flag */
@@ -927,6 +929,7 @@ static void usa49wg_indat_callback(struct urb *urb)
                         }
                         if (port->port.count)
                                 tty_flip_buffer_push(tty);
+                        tty_kref_put(tty);
                 }
         }
 
@@ -967,8 +970,8 @@ static void usa90_indat_callback(struct urb *urb)
         port =  urb->context;
         p_priv = usb_get_serial_port_data(port);
 
-        tty = port->port.tty;
         if (urb->actual_length) {
+                tty = tty_port_tty_get(&port->port);
                 /* if current mode is DMA, looks like usa28 format
                    otherwise looks like usa26 data format */
 
@@ -1004,6 +1007,7 @@ static void usa90_indat_callback(struct urb *urb)
                         }
                 }
                 tty_flip_buffer_push(tty);
+                tty_kref_put(tty);
         }
 
         /* Resubmit urb so we continue receiving */
@@ -1025,6 +1029,7 @@ static void	usa90_instat_callback(struct urb *urb)
         struct usb_serial                       *serial;
         struct usb_serial_port                  *port;
         struct keyspan_port_private             *p_priv;
+        struct tty_struct                       *tty;
         int old_dcd_state, err;
         int status = urb->status;
 
@@ -1053,12 +1058,11 @@ static void	usa90_instat_callback(struct urb *urb)
         p_priv->dcd_state = ((msg->dcd) ? 1 : 0);
         p_priv->ri_state = ((msg->ri) ? 1 : 0);
 
-        if (port->port.tty && !C_CLOCAL(port->port.tty)
-            && old_dcd_state != p_priv->dcd_state) {
-                if (old_dcd_state)
-                        tty_hangup(port->port.tty);
-                /*  else */
-                /*      wake_up_interruptible(&p_priv->open_wait); */
+        if (old_dcd_state != p_priv->dcd_state && old_dcd_state) {
+                tty = tty_port_tty_get(&port->port);
+                if (tty && !C_CLOCAL(tty))
+                        tty_hangup(tty);
+                tty_kref_put(tty);
         }
 
         /* Resubmit urb so we continue receiving */
@@ -1130,12 +1134,11 @@ static void	usa67_instat_callback(struct urb *urb)
         p_priv->cts_state = ((msg->hskia_cts) ? 1 : 0);
         p_priv->dcd_state = ((msg->gpia_dcd) ? 1 : 0);
 
-        if (port->port.tty && !C_CLOCAL(port->port.tty)
-            && old_dcd_state != p_priv->dcd_state) {
-                if (old_dcd_state)
-                        tty_hangup(port->port.tty);
-                /*  else */
-                /*      wake_up_interruptible(&p_priv->open_wait); */
+        if (old_dcd_state != p_priv->dcd_state && old_dcd_state) {
+                struct tty_struct *tty = tty_port_tty_get(&port->port);
+                if (tty && !C_CLOCAL(tty))
+                        tty_hangup(tty);
+                tty_kref_put(tty);
         }
 
         /* Resubmit urb so we continue receiving */
@@ -1332,7 +1335,7 @@ static void keyspan_close(struct tty_struct *tty,
                         stop_urb(p_priv->out_urbs[i]);
                 }
         }
-        port->port.tty = NULL;
+        tty_port_tty_set(&port->port, NULL);
 }
 
 /* download the firmware to a pre-renumeration device */
diff --git a/drivers/usb/serial/keyspan_pda.c b/drivers/usb/serial/keyspan_pda.c
index 040040a267d9..99e9a14c5bf6 100644
--- a/drivers/usb/serial/keyspan_pda.c
+++ b/drivers/usb/serial/keyspan_pda.c
@@ -172,8 +172,9 @@ static void keyspan_pda_wakeup_write(struct work_struct *work)
         struct keyspan_pda_private *priv =
                 container_of(work, struct keyspan_pda_private, wakeup_work);
         struct usb_serial_port *port = priv->port;
-
-        tty_wakeup(port->port.tty);
+        struct tty_struct *tty = tty_port_tty_get(&port->port);
+        tty_wakeup(tty);
+        tty_kref_put(tty);
 }
 
 static void keyspan_pda_request_unthrottle(struct work_struct *work)
@@ -205,7 +206,7 @@ static void keyspan_pda_request_unthrottle(struct work_struct *work)
 static void keyspan_pda_rx_interrupt(struct urb *urb)
 {
         struct usb_serial_port *port = urb->context;
-        struct tty_struct *tty = port->port.tty;
+        struct tty_struct *tty = tty_port_tty_get(&port->port);
         unsigned char *data = urb->transfer_buffer;
         int retval;
         int status = urb->status;
@@ -222,7 +223,7 @@ static void keyspan_pda_rx_interrupt(struct urb *urb)
                 /* this urb is terminated, clean up */
                 dbg("%s - urb shutting down with status: %d",
                     __func__, status);
-                return;
+                goto out;
         default:
                 dbg("%s - nonzero urb status received: %d",
                     __func__, status);
@@ -261,8 +262,11 @@ static void keyspan_pda_rx_interrupt(struct urb *urb)
 exit:
         retval = usb_submit_urb(urb, GFP_ATOMIC);
         if (retval)
-                err("%s - usb_submit_urb failed with result %d",
-                     __func__, retval);
+                dev_err(&port->dev,
+                        "%s - usb_submit_urb failed with result %d",
+                        __func__, retval);
+out:
+        tty_kref_put(tty);                   
 }
 
 
diff --git a/drivers/usb/serial/kl5kusb105.c b/drivers/usb/serial/kl5kusb105.c
index b84dddc71124..ff3a07f5102f 100644
--- a/drivers/usb/serial/kl5kusb105.c
+++ b/drivers/usb/serial/kl5kusb105.c
@@ -658,7 +658,7 @@ static void klsi_105_read_bulk_callback(struct urb *urb)
         } else {
                 int bytes_sent = ((__u8 *) data)[0] +
                                  ((unsigned int) ((__u8 *) data)[1] << 8);
-                tty = port->port.tty;
+                tty = tty_port_tty_get(&port->port);
                 /* we should immediately resubmit the URB, before attempting
                  * to pass the data on to the tty layer. But that needs locking
                  * against re-entry an then mixed-up data because of
@@ -679,6 +679,7 @@ static void klsi_105_read_bulk_callback(struct urb *urb)
                 tty_buffer_request_room(tty, bytes_sent);
                 tty_insert_flip_string(tty, data + 2, bytes_sent);
                 tty_flip_buffer_push(tty);
+                tty_kref_put(tty);
 
                 /* again lockless, but debug info only */
                 priv->bytes_in += bytes_sent;
diff --git a/drivers/usb/serial/kobil_sct.c b/drivers/usb/serial/kobil_sct.c
index deba28ec77e8..cfcf37c2b957 100644
--- a/drivers/usb/serial/kobil_sct.c
+++ b/drivers/usb/serial/kobil_sct.c
@@ -383,7 +383,7 @@ static void kobil_read_int_callback(struct urb *urb)
                 return;
         }
 
-        tty = port->port.tty;
+        tty = tty_port_tty_get(&port->port);
         if (urb->actual_length) {
 
                 /* BEGIN DEBUG */
@@ -405,6 +405,7 @@ static void kobil_read_int_callback(struct urb *urb)
                 tty_insert_flip_string(tty, data, urb->actual_length);
                 tty_flip_buffer_push(tty);
         }
+        tty_kref_put(tty);
         /* someone sets the dev to 0 if the close method has been called */
         port->interrupt_in_urb->dev = port->serial->dev;
 
diff --git a/drivers/usb/serial/mct_u232.c b/drivers/usb/serial/mct_u232.c
index 0ded8bd6ec85..9b2cef81cde0 100644
--- a/drivers/usb/serial/mct_u232.c
+++ b/drivers/usb/serial/mct_u232.c
@@ -563,10 +563,11 @@ static void mct_u232_read_int_callback(struct urb *urb)
          * Work-a-round: handle the 'usual' bulk-in pipe here
          */
         if (urb->transfer_buffer_length > 2) {
-                tty = port->port.tty;
+                tty = tty_port_tty_get(&port->port);
                 if (urb->actual_length) {
                         tty_insert_flip_string(tty, data, urb->actual_length);
                         tty_flip_buffer_push(tty);
+                        tty_kref_put(tty);
                 }
                 goto exit;
         }
@@ -591,7 +592,7 @@ static void mct_u232_read_int_callback(struct urb *urb)
          * to look in to this before committing any code.
          */
         if (priv->last_lsr & MCT_U232_LSR_ERR) {
-                tty = port->port.tty;
+                tty = tty_port_tty_get(&port->port);
                 /* Overrun Error */
                 if (priv->last_lsr & MCT_U232_LSR_OE) {
                 }
@@ -604,6 +605,7 @@ static void mct_u232_read_int_callback(struct urb *urb)
                 /* Break Indicator */
                 if (priv->last_lsr & MCT_U232_LSR_BI) {
                 }
+                tty_kref_put(tty);
         }
 #endif
         spin_unlock_irqrestore(&priv->lock, flags);
diff --git a/drivers/usb/serial/mos7720.c b/drivers/usb/serial/mos7720.c
index 7c4917d77c0a..7b538caec37f 100644
--- a/drivers/usb/serial/mos7720.c
+++ b/drivers/usb/serial/mos7720.c
@@ -216,12 +216,13 @@ static void mos7720_bulk_in_callback(struct urb *urb)
 
         data = urb->transfer_buffer;
 
-        tty = port->port.tty;
+        tty = tty_port_tty_get(&port->port);
         if (tty && urb->actual_length) {
                 tty_buffer_request_room(tty, urb->actual_length);
                 tty_insert_flip_string(tty, data, urb->actual_length);
                 tty_flip_buffer_push(tty);
         }
+        tty_kref_put(tty);
 
         if (!port->read_urb) {
                 dbg("URB KILLED !!!");
@@ -262,10 +263,11 @@ static void mos7720_bulk_out_data_callback(struct urb *urb)
 
         dbg("Entering .........");
 
-        tty = mos7720_port->port->port.tty;
+        tty = tty_port_tty_get(&mos7720_port->port->port);
 
         if (tty && mos7720_port->open)
                 tty_wakeup(tty);
+        tty_kref_put(tty);
 }
 
 /*
@@ -1267,29 +1269,6 @@ static int get_lsr_info(struct tty_struct *tty,
         return 0;
 }
 
-/*
- * get_number_bytes_avail - get number of bytes available
- *
- * Purpose: Let user call ioctl to get the count of number of bytes available.
- */
-static int get_number_bytes_avail(struct moschip_port *mos7720_port,
-                                  unsigned int __user *value)
-{
-        unsigned int result = 0;
-        struct tty_struct *tty = mos7720_port->port->port.tty;
-
-        if (!tty)
-                return -ENOIOCTLCMD;
-
-        result = tty->read_cnt;
-
-        dbg("%s(%d) = %d", __func__,  mos7720_port->port->number, result);
-        if (copy_to_user(value, &result, sizeof(int)))
-                return -EFAULT;
-
-        return -ENOIOCTLCMD;
-}
-
 static int set_modem_info(struct moschip_port *mos7720_port, unsigned int cmd,
                           unsigned int __user *value)
 {
@@ -1409,13 +1388,6 @@ static int mos7720_ioctl(struct tty_struct *tty, struct file *file,
         dbg("%s - port %d, cmd = 0x%x", __func__, port->number, cmd);
 
         switch (cmd) {
-        case TIOCINQ:
-                /* return number of bytes available */
-                dbg("%s (%d) TIOCINQ", __func__,  port->number);
-                return get_number_bytes_avail(mos7720_port,
-                                              (unsigned int __user *)arg);
-                break;
-
         case TIOCSERGETLSR:
                 dbg("%s (%d) TIOCSERGETLSR", __func__,  port->number);
                 return get_lsr_info(tty, mos7720_port,
diff --git a/drivers/usb/serial/mos7840.c b/drivers/usb/serial/mos7840.c
index 09d82062b973..60543d79ef56 100644
--- a/drivers/usb/serial/mos7840.c
+++ b/drivers/usb/serial/mos7840.c
@@ -709,12 +709,13 @@ static void mos7840_bulk_in_callback(struct urb *urb)
         dbg("%s", "Entering ........... \n");
 
         if (urb->actual_length) {
-                tty = mos7840_port->port->port.tty;
+                tty = tty_port_tty_get(&mos7840_port->port->port);
                 if (tty) {
                         tty_buffer_request_room(tty, urb->actual_length);
                         tty_insert_flip_string(tty, data, urb->actual_length);
                         dbg(" %s \n", data);
                         tty_flip_buffer_push(tty);
+                        tty_kref_put(tty);
                 }
                 mos7840_port->icount.rx += urb->actual_length;
                 smp_wmb();
@@ -773,10 +774,10 @@ static void mos7840_bulk_out_data_callback(struct urb *urb)
 
         dbg("%s \n", "Entering .........");
 
-        tty = mos7840_port->port->port.tty;
-
+        tty = tty_port_tty_get(&mos7840_port->port->port);
         if (tty && mos7840_port->open)
                 tty_wakeup(tty);
+        tty_kref_put(tty);
 
 }
 
diff --git a/drivers/usb/serial/navman.c b/drivers/usb/serial/navman.c
index d6736531a0fa..bcdcbb822705 100644
--- a/drivers/usb/serial/navman.c
+++ b/drivers/usb/serial/navman.c
@@ -64,12 +64,13 @@ static void navman_read_int_callback(struct urb *urb)
         usb_serial_debug_data(debug, &port->dev, __func__,
                               urb->actual_length, data);
 
-        tty = port->port.tty;
+        tty = tty_port_tty_get(&port->port);
         if (tty && urb->actual_length) {
                 tty_buffer_request_room(tty, urb->actual_length);
                 tty_insert_flip_string(tty, data, urb->actual_length);
                 tty_flip_buffer_push(tty);
         }
+        tty_kref_put(tty);
 
 exit:
         result = usb_submit_urb(urb, GFP_ATOMIC);
diff --git a/drivers/usb/serial/omninet.c b/drivers/usb/serial/omninet.c
index ae8e227f3db2..c4d70b0f1e48 100644
--- a/drivers/usb/serial/omninet.c
+++ b/drivers/usb/serial/omninet.c
@@ -172,7 +172,7 @@ static int omninet_open(struct tty_struct *tty,
         dbg("%s - port %d", __func__, port->number);
 
         wport = serial->port[1];
-        wport->port.tty = tty;          /* FIXME */
+        tty_port_tty_set(&wport->port, tty);
 
         /* Start reading from the device */
         usb_fill_bulk_urb(port->read_urb, serial->dev,
@@ -229,9 +229,11 @@ static void omninet_read_bulk_callback(struct urb *urb)
         }
 
         if (urb->actual_length && header->oh_len) {
-                tty_insert_flip_string(port->port.tty,
-                        data + OMNINET_DATAOFFSET, header->oh_len);
-                tty_flip_buffer_push(port->port.tty);
+                struct tty_struct *tty = tty_port_tty_get(&port->port);
+                tty_insert_flip_string(tty, data + OMNINET_DATAOFFSET,
+                                                        header->oh_len);
+                tty_flip_buffer_push(tty);
+                tty_kref_put(tty);
         }
 
         /* Continue trying to always read  */
diff --git a/drivers/usb/serial/option.c b/drivers/usb/serial/option.c
index 73f8277f88f2..6b1727e751e3 100644
--- a/drivers/usb/serial/option.c
+++ b/drivers/usb/serial/option.c
@@ -571,14 +571,14 @@ static void option_indat_callback(struct urb *urb)
                 dbg("%s: nonzero status: %d on endpoint %02x.",
                     __func__, status, endpoint);
         } else {
-                tty = port->port.tty;
+                tty = tty_port_tty_get(&port->port);
                 if (urb->actual_length) {
                         tty_buffer_request_room(tty, urb->actual_length);
                         tty_insert_flip_string(tty, data, urb->actual_length);
                         tty_flip_buffer_push(tty);
-                } else {
+                } else 
                         dbg("%s: empty read urb received", __func__);
-                }
+                tty_kref_put(tty);
 
                 /* Resubmit urb so we continue receiving */
                 if (port->port.count && status != -ESHUTDOWN) {
@@ -647,9 +647,13 @@ static void option_instat_callback(struct urb *urb)
                         portdata->dsr_state = ((signals & 0x02) ? 1 : 0);
                         portdata->ri_state = ((signals & 0x08) ? 1 : 0);
 
-                        if (port->port.tty && !C_CLOCAL(port->port.tty) &&
-                                        old_dcd_state && !portdata->dcd_state)
-                                tty_hangup(port->port.tty);
+                        if (old_dcd_state && !portdata->dcd_state) {
+                                struct tty_struct *tty =
+                                                tty_port_tty_get(&port->port);
+                                if (tty && !C_CLOCAL(tty))
+                                        tty_hangup(tty);
+                                tty_kref_put(tty);
+                        }
                 } else {
                         dbg("%s: type %x req %x", __func__,
                                 req_pkt->bRequestType, req_pkt->bRequest);
@@ -793,7 +797,7 @@ static void option_close(struct tty_struct *tty,
                 for (i = 0; i < N_OUT_URB; i++)
                         usb_kill_urb(portdata->out_urbs[i]);
         }
-        port->port.tty = NULL;  /* FIXME */
+        tty_port_tty_set(&port->port, NULL);
 }
 
 /* Helper functions used by option_setup_urbs */
diff --git a/drivers/usb/serial/oti6858.c b/drivers/usb/serial/oti6858.c
index 42f92815c6e5..ba551f00f16f 100644
--- a/drivers/usb/serial/oti6858.c
+++ b/drivers/usb/serial/oti6858.c
@@ -998,11 +998,12 @@ static void oti6858_read_bulk_callback(struct urb *urb)
                 return;
         }
 
-        tty = port->port.tty;
+        tty = tty_port_tty_get(&port->port);
         if (tty != NULL && urb->actual_length > 0) {
                 tty_insert_flip_string(tty, data, urb->actual_length);
                 tty_flip_buffer_push(tty);
         }
+        tty_kref_put(tty);
 
         /* schedule the interrupt urb if we are still open */
         if (port->port.count != 0) {
diff --git a/drivers/usb/serial/pl2303.c b/drivers/usb/serial/pl2303.c
index 8d6006894bf5..908437847165 100644
--- a/drivers/usb/serial/pl2303.c
+++ b/drivers/usb/serial/pl2303.c
@@ -1046,7 +1046,7 @@ static void pl2303_read_bulk_callback(struct urb *urb)
                 tty_flag = TTY_FRAME;
         dbg("%s - tty_flag = %d", __func__, tty_flag);
 
-        tty = port->port.tty;
+        tty = tty_port_tty_get(&port->port);
         if (tty && urb->actual_length) {
                 tty_buffer_request_room(tty, urb->actual_length + 1);
                 /* overrun is special, not associated with a char */
@@ -1056,7 +1056,7 @@ static void pl2303_read_bulk_callback(struct urb *urb)
                         tty_insert_flip_char(tty, data[i], tty_flag);
                 tty_flip_buffer_push(tty);
         }
-
+        tty_kref_put(tty);
         /* Schedule the next read _if_ we are still open */
         if (port->port.count) {
                 urb->dev = port->serial->dev;
diff --git a/drivers/usb/serial/safe_serial.c b/drivers/usb/serial/safe_serial.c
index def52d07a4ea..72903ac9f5c0 100644
--- a/drivers/usb/serial/safe_serial.c
+++ b/drivers/usb/serial/safe_serial.c
@@ -217,6 +217,7 @@ static void safe_read_bulk_callback(struct urb *urb)
         struct usb_serial_port *port =  urb->context;
         unsigned char *data = urb->transfer_buffer;
         unsigned char length = urb->actual_length;
+        struct tty_struct *tty;
         int result;
         int status = urb->status;
 
@@ -242,6 +243,7 @@ static void safe_read_bulk_callback(struct urb *urb)
                 printk("\n");
         }
 #endif
+        tty = tty_port_tty_get(&port->port);
         if (safe) {
                 __u16 fcs;
                 fcs = fcs_compute10(data, length, CRC10_INITFCS);
@@ -250,9 +252,9 @@ static void safe_read_bulk_callback(struct urb *urb)
                         if (actual_length <= (length - 2)) {
                                 info("%s - actual: %d", __func__,
                                                         actual_length);
-                                tty_insert_flip_string(port->port.tty,
+                                tty_insert_flip_string(tty,
                                                         data, actual_length);
-                                tty_flip_buffer_push(port->port.tty);
+                                tty_flip_buffer_push(tty);
                         } else {
                                 err("%s - inconsistent lengths %d:%d",
                                         __func__, actual_length, length);
@@ -261,9 +263,10 @@ static void safe_read_bulk_callback(struct urb *urb)
                         err("%s - bad CRC %x", __func__, fcs);
                 }
         } else {
-                tty_insert_flip_string(port->port.tty, data, length);
-                tty_flip_buffer_push(port->port.tty);
+                tty_insert_flip_string(tty, data, length);
+                tty_flip_buffer_push(tty);
         }
+        tty_kref_put(tty);
 
         /* Continue trying to always read  */
         usb_fill_bulk_urb(urb, port->serial->dev,
diff --git a/drivers/usb/serial/sierra.c b/drivers/usb/serial/sierra.c
index ea1a103c99be..8b9eaf383679 100644
--- a/drivers/usb/serial/sierra.c
+++ b/drivers/usb/serial/sierra.c
@@ -440,14 +440,14 @@ static void sierra_indat_callback(struct urb *urb)
                 dbg("%s: nonzero status: %d on endpoint %02x.",
                     __func__, status, endpoint);
         } else {
-                tty = port->port.tty;
                 if (urb->actual_length) {
+                tty = tty_port_tty_get(&port->port);
                         tty_buffer_request_room(tty, urb->actual_length);
                         tty_insert_flip_string(tty, data, urb->actual_length);
                         tty_flip_buffer_push(tty);
-                } else {
+                        tty_kref_put(tty);
+                } else
                         dbg("%s: empty read urb received", __func__);
-                }
 
                 /* Resubmit urb so we continue receiving */
                 if (port->port.count && status != -ESHUTDOWN) {
@@ -485,6 +485,7 @@ static void sierra_instat_callback(struct urb *urb)
                         unsigned char signals = *((unsigned char *)
                                         urb->transfer_buffer +
                                         sizeof(struct usb_ctrlrequest));
+                        struct tty_struct *tty;
 
                         dbg("%s: signal x%x", __func__, signals);
 
@@ -494,9 +495,11 @@ static void sierra_instat_callback(struct urb *urb)
                         portdata->dsr_state = ((signals & 0x02) ? 1 : 0);
                         portdata->ri_state = ((signals & 0x08) ? 1 : 0);
 
-                        if (port->port.tty && !C_CLOCAL(port->port.tty) &&
+                        tty = tty_port_tty_get(&port->port);
+                        if (tty && !C_CLOCAL(tty) &&
                                         old_dcd_state && !portdata->dcd_state)
-                                tty_hangup(port->port.tty);
+                                tty_hangup(tty);
+                        tty_kref_put(tty);
                 } else {
                         dbg("%s: type %x req %x", __func__,
                                 req_pkt->bRequestType, req_pkt->bRequest);
@@ -616,8 +619,7 @@ static void sierra_close(struct tty_struct *tty,
         }
 
         usb_kill_urb(port->interrupt_in_urb);
-
-        port->port.tty = NULL;  /* FIXME */
+        tty_port_tty_set(&port->port, NULL);
 }
 
 static int sierra_startup(struct usb_serial *serial)
diff --git a/drivers/usb/serial/spcp8x5.c b/drivers/usb/serial/spcp8x5.c
index 283cf6b36b2c..1533d6e12238 100644
--- a/drivers/usb/serial/spcp8x5.c
+++ b/drivers/usb/serial/spcp8x5.c
@@ -755,7 +755,7 @@ static void spcp8x5_read_bulk_callback(struct urb *urb)
                 tty_flag = TTY_FRAME;
         dev_dbg(&port->dev, "tty_flag = %d\n", tty_flag);
 
-        tty = port->port.tty;
+        tty = tty_port_tty_get(&port->port);
         if (tty && urb->actual_length) {
                 tty_buffer_request_room(tty, urb->actual_length + 1);
                 /* overrun is special, not associated with a char */
@@ -765,6 +765,7 @@ static void spcp8x5_read_bulk_callback(struct urb *urb)
                         tty_insert_flip_char(tty, data[i], tty_flag);
                 tty_flip_buffer_push(tty);
         }
+        tty_kref_put(tty);
 
         /* Schedule the next read _if_ we are still open */
         if (port->port.count) {
diff --git a/drivers/usb/serial/ti_usb_3410_5052.c b/drivers/usb/serial/ti_usb_3410_5052.c
index 9a3e495c769c..c90237d48b0e 100644
--- a/drivers/usb/serial/ti_usb_3410_5052.c
+++ b/drivers/usb/serial/ti_usb_3410_5052.c
@@ -179,7 +179,7 @@ static int ti_set_mcr(struct ti_port *tport, unsigned int mcr);
 static int ti_get_lsr(struct ti_port *tport);
 static int ti_get_serial_info(struct ti_port *tport,
         struct serial_struct __user *ret_arg);
-static int ti_set_serial_info(struct ti_port *tport,
+static int ti_set_serial_info(struct tty_struct *tty, struct ti_port *tport,
         struct serial_struct __user *new_arg);
 static void ti_handle_new_msr(struct ti_port *tport, __u8 msr);
 
@@ -857,8 +857,8 @@ static int ti_ioctl(struct tty_struct *tty, struct file *file,
                                 (struct serial_struct __user *)arg);
         case TIOCSSERIAL:
                 dbg("%s - (%d) TIOCSSERIAL", __func__, port->number);
-                return ti_set_serial_info(tport,
-                                        (struct serial_struct __user *)arg);
+                return ti_set_serial_info(tty, tport,
+                                (struct serial_struct __user *)arg);
         case TIOCMIWAIT:
                 dbg("%s - (%d) TIOCMIWAIT", __func__, port->number);
                 cprev = tport->tp_icount;
@@ -1211,6 +1211,7 @@ static void ti_bulk_in_callback(struct urb *urb)
         struct device *dev = &urb->dev->dev;
         int status = urb->status;
         int retval = 0;
+        struct tty_struct *tty;
 
         dbg("%s", __func__);
 
@@ -1239,20 +1240,22 @@ static void ti_bulk_in_callback(struct urb *urb)
                 return;
         }
 
-        if (port->port.tty && urb->actual_length) {
+        tty = tty_port_tty_get(&port->port);
+        if (tty && urb->actual_length) {
                 usb_serial_debug_data(debug, dev, __func__,
                         urb->actual_length, urb->transfer_buffer);
 
                 if (!tport->tp_is_open)
                         dbg("%s - port closed, dropping data", __func__);
                 else
-                        ti_recv(&urb->dev->dev, port->port.tty,
+                        ti_recv(&urb->dev->dev, tty,
                                                 urb->transfer_buffer,
                                                 urb->actual_length);
 
                 spin_lock(&tport->tp_lock);
                 tport->tp_icount.rx += urb->actual_length;
                 spin_unlock(&tport->tp_lock);
+                tty_kref_put(tty);
         }
 
 exit:
@@ -1330,7 +1333,7 @@ static void ti_send(struct ti_port *tport)
 {
         int count, result;
         struct usb_serial_port *port = tport->tp_port;
-        struct tty_struct *tty = port->port.tty;        /* FIXME */
+        struct tty_struct *tty = tty_port_tty_get(&port->port); /* FIXME */
         unsigned long flags;
 
 
@@ -1338,19 +1341,15 @@ static void ti_send(struct ti_port *tport)
 
         spin_lock_irqsave(&tport->tp_lock, flags);
 
-        if (tport->tp_write_urb_in_use) {
-                spin_unlock_irqrestore(&tport->tp_lock, flags);
-                return;
-        }
+        if (tport->tp_write_urb_in_use)
+                goto unlock;
 
         count = ti_buf_get(tport->tp_write_buf,
                                 port->write_urb->transfer_buffer,
                                 port->bulk_out_size);
 
-        if (count == 0) {
-                spin_unlock_irqrestore(&tport->tp_lock, flags);
-                return;
-        }
+        if (count == 0)
+                goto unlock;
 
         tport->tp_write_urb_in_use = 1;
 
@@ -1380,7 +1379,13 @@ static void ti_send(struct ti_port *tport)
         /* more room in the buffer for new writes, wakeup */
         if (tty)
                 tty_wakeup(tty);
+        tty_kref_put(tty);
         wake_up_interruptible(&tport->tp_write_wait);
+        return;
+unlock:
+        spin_unlock_irqrestore(&tport->tp_lock, flags);
+        tty_kref_put(tty);
+        return;
 }
 
 
@@ -1464,20 +1469,16 @@ static int ti_get_serial_info(struct ti_port *tport,
 }
 
 
-static int ti_set_serial_info(struct ti_port *tport,
+static int ti_set_serial_info(struct tty_struct *tty, struct ti_port *tport,
         struct serial_struct __user *new_arg)
 {
-        struct usb_serial_port *port = tport->tp_port;
         struct serial_struct new_serial;
 
         if (copy_from_user(&new_serial, new_arg, sizeof(new_serial)))
                 return -EFAULT;
 
         tport->tp_flags = new_serial.flags & TI_SET_SERIAL_FLAGS;
-        /* FIXME */
-        if (port->port.tty)
-                port->port.tty->low_latency =
-                        (tport->tp_flags & ASYNC_LOW_LATENCY) ? 1 : 0;
+        tty->low_latency = (tport->tp_flags & ASYNC_LOW_LATENCY) ? 1 : 0;
         tport->tp_closing_wait = new_serial.closing_wait;
 
         return 0;
@@ -1510,7 +1511,7 @@ static void ti_handle_new_msr(struct ti_port *tport, __u8 msr)
         tport->tp_msr = msr & TI_MSR_MASK;
 
         /* handle CTS flow control */
-        tty = tport->tp_port->port.tty;
+        tty = tty_port_tty_get(&tport->tp_port->port);
         if (tty && C_CRTSCTS(tty)) {
                 if (msr & TI_MSR_CTS) {
                         tty->hw_stopped = 0;
@@ -1519,6 +1520,7 @@ static void ti_handle_new_msr(struct ti_port *tport, __u8 msr)
                         tty->hw_stopped = 1;
                 }
         }
+        tty_kref_put(tty);
 }
 
 
diff --git a/drivers/usb/serial/usb-serial.c b/drivers/usb/serial/usb-serial.c
index 4f7f9e3ae0a4..e7d4246027b2 100644
--- a/drivers/usb/serial/usb-serial.c
+++ b/drivers/usb/serial/usb-serial.c
@@ -214,7 +214,7 @@ static int serial_open (struct tty_struct *tty, struct file *filp)
         /* set up our port structure making the tty driver
          * remember our port object, and us it */
         tty->driver_data = port;
-        port->port.tty = tty;
+        tty_port_tty_set(&port->port, tty);
 
         if (port->port.count == 1) {
 
@@ -246,7 +246,7 @@ bailout_module_put:
 bailout_mutex_unlock:
         port->port.count = 0;
         tty->driver_data = NULL;
-        port->port.tty = NULL;
+        tty_port_tty_set(&port->port, NULL);
         mutex_unlock(&port->mutex);
 bailout_kref_put:
         usb_serial_put(serial);
@@ -276,10 +276,11 @@ static void serial_close(struct tty_struct *tty, struct file *filp)
                 port->serial->type->close(tty, port, filp);
 
         if (port->port.count == (port->console? 1 : 0)) {
-                if (port->port.tty) {
-                        if (port->port.tty->driver_data)
-                                port->port.tty->driver_data = NULL;
-                        port->port.tty = NULL;
+                struct tty_struct *tty = tty_port_tty_get(&port->port);
+                if (tty) {
+                        if (tty->driver_data)
+                                tty->driver_data = NULL;
+                        tty_port_tty_set(&port->port, NULL);
                 }
         }
 
@@ -508,11 +509,12 @@ static void usb_serial_port_work(struct work_struct *work)
         if (!port)
                 return;
 
-        tty = port->port.tty;
+        tty = tty_port_tty_get(&port->port);
         if (!tty)
                 return;
 
         tty_wakeup(tty);
+        tty_kref_put(tty);
 }
 
 static void port_release(struct device *dev)
@@ -819,6 +821,7 @@ int usb_serial_probe(struct usb_interface *interface,
                 port = kzalloc(sizeof(struct usb_serial_port), GFP_KERNEL);
                 if (!port)
                         goto probe_error;
+                tty_port_init(&port->port);
                 port->serial = serial;
                 spin_lock_init(&port->lock);
                 mutex_init(&port->mutex);
@@ -1040,8 +1043,11 @@ void usb_serial_disconnect(struct usb_interface *interface)
         for (i = 0; i < serial->num_ports; ++i) {
                 port = serial->port[i];
                 if (port) {
-                        if (port->port.tty)
-                                tty_hangup(port->port.tty);
+                        struct tty_struct *tty = tty_port_tty_get(&port->port);
+                        if (tty) {
+                                tty_hangup(tty);
+                                tty_kref_put(tty);
+                        }
                         kill_traffic(port);
                 }
         }
diff --git a/drivers/usb/serial/visor.c b/drivers/usb/serial/visor.c
index cf8924f9a2cc..a6d1c75a1c89 100644
--- a/drivers/usb/serial/visor.c
+++ b/drivers/usb/serial/visor.c
@@ -499,7 +499,7 @@ static void visor_read_bulk_callback(struct urb *urb)
         int status = urb->status;
         struct tty_struct *tty;
         int result;
-        int available_room;
+        int available_room = 0;
 
         dbg("%s - port %d", __func__, port->number);
 
@@ -512,13 +512,17 @@ static void visor_read_bulk_callback(struct urb *urb)
         usb_serial_debug_data(debug, &port->dev, __func__,
                                                 urb->actual_length, data);
 
-        tty = port->port.tty;
-        if (tty && urb->actual_length) {
-                available_room = tty_buffer_request_room(tty,
+        if (urb->actual_length) {
+                tty = tty_port_tty_get(&port->port);
+                if (tty) {
+                        available_room = tty_buffer_request_room(tty,
                                                         urb->actual_length);
-                if (available_room) {
-                        tty_insert_flip_string(tty, data, available_room);
-                        tty_flip_buffer_push(tty);
+                        if (available_room) {
+                                tty_insert_flip_string(tty, data,
+                                                        available_room);
+                                tty_flip_buffer_push(tty);
+                        }
+                        tty_kref_put(tty);
                 }
                 spin_lock(&priv->lock);
                 priv->bytes_in += available_room;
diff --git a/drivers/usb/serial/whiteheat.c b/drivers/usb/serial/whiteheat.c
index 3a9d14384a43..11c8b97a5177 100644
--- a/drivers/usb/serial/whiteheat.c
+++ b/drivers/usb/serial/whiteheat.c
@@ -1481,7 +1481,7 @@ static void rx_data_softint(struct work_struct *work)
         struct whiteheat_private *info =
                 container_of(work, struct whiteheat_private, rx_work);
         struct usb_serial_port *port = info->port;
-        struct tty_struct *tty = port->port.tty;
+        struct tty_struct *tty = tty_port_tty_get(&port->port);
         struct whiteheat_urb_wrap *wrap;
         struct urb *urb;
         unsigned long flags;
@@ -1493,7 +1493,7 @@ static void rx_data_softint(struct work_struct *work)
         spin_lock_irqsave(&info->lock, flags);
         if (info->flags & THROTTLED) {
                 spin_unlock_irqrestore(&info->lock, flags);
-                return;
+                goto out;
         }
 
         list_for_each_safe(tmp, tmp2, &info->rx_urb_q) {
@@ -1513,7 +1513,7 @@ static void rx_data_softint(struct work_struct *work)
                                 spin_unlock_irqrestore(&info->lock, flags);
                                 tty_flip_buffer_push(tty);
                                 schedule_work(&info->rx_work);
-                                return;
+                                goto out;
                         }
                         tty_insert_flip_string(tty, urb->transfer_buffer, len);
                         sent += len;
@@ -1536,6 +1536,8 @@ static void rx_data_softint(struct work_struct *work)
 
         if (sent)
                 tty_flip_buffer_push(tty);
+out:
+        tty_kref_put(tty);
 }
 
 
diff --git a/include/linux/tty.h b/include/linux/tty.h
index b64d10b66548..c30ed8d3bcbd 100644
--- a/include/linux/tty.h
+++ b/include/linux/tty.h
@@ -182,6 +182,7 @@ struct signal_struct;
 
 struct tty_port {
         struct tty_struct       *tty;           /* Back pointer */
+        spinlock_t              lock;           /* Lock protecting tty field */
         int                     blocked_open;   /* Waiting to open */
         int                     count;          /* Usage count */
         wait_queue_head_t       open_wait;      /* Open waiters */
@@ -405,6 +406,8 @@ extern int tty_write_lock(struct tty_struct *tty, int ndelay);
 extern void tty_port_init(struct tty_port *port);
 extern int tty_port_alloc_xmit_buf(struct tty_port *port);
 extern void tty_port_free_xmit_buf(struct tty_port *port);
+extern struct tty_struct *tty_port_tty_get(struct tty_port *port);
+extern void tty_port_tty_set(struct tty_port *port, struct tty_struct *tty);
 
 extern int tty_register_ldisc(int disc, struct tty_ldisc_ops *new_ldisc);
 extern int tty_unregister_ldisc(int disc);