[PATCH] isdn4linux: Siemens Gigaset drivers - tty interface

And: Tilman Schmidt <tilman@imap.cc>

This patch adds the tty interface to the gigaset module.  The tty interface
provides direct access to the AT command set of the Gigaset devices.

Signed-off-by: Hansjoerg Lipp <hjlipp@web.de>
Signed-off-by: Tilman Schmidt <tilman@imap.cc>
Cc: Karsten Keil <kkeil@suse.de>
Cc: Greg KH <greg@kroah.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 718 insertions, 0 deletions

diff --git a/drivers/isdn/gigaset/interface.c b/drivers/isdn/gigaset/interface.c
new file mode 100644
index 000000000000..3a81d9c65141
--- /dev/null
+++ b/drivers/isdn/gigaset/interface.c
@@ -0,0 +1,718 @@
+/*
+ * interface to user space for the gigaset driver
+ *
+ * Copyright (c) 2004 by Hansjoerg Lipp <hjlipp@web.de>
+ *
+ * =====================================================================
+ *    This program is free software; you can redistribute it and/or
+ *    modify it under the terms of the GNU General Public License as
+ *    published by the Free Software Foundation; either version 2 of
+ *    the License, or (at your option) any later version.
+ * =====================================================================
+ * Version: $Id: interface.c,v 1.14.4.15 2006/02/04 18:28:16 hjlipp Exp $
+ * =====================================================================
+ */
+
+#include "gigaset.h"
+#include <linux/gigaset_dev.h>
+#include <linux/tty.h>
+#include <linux/tty_flip.h>
+
+/*** our ioctls ***/
+
+static int if_lock(struct cardstate *cs, int *arg)
+{
+        int cmd = *arg;
+
+        dbg(DEBUG_IF, "%u: if_lock (%d)", cs->minor_index, cmd);
+
+        if (cmd > 1)
+                return -EINVAL;
+
+        if (cmd < 0) {
+                *arg = atomic_read(&cs->mstate) == MS_LOCKED; //FIXME remove?
+                return 0;
+        }
+
+        if (!cmd && atomic_read(&cs->mstate) == MS_LOCKED
+            && atomic_read(&cs->connected)) {
+                cs->ops->set_modem_ctrl(cs, 0, TIOCM_DTR|TIOCM_RTS);
+                cs->ops->baud_rate(cs, B115200);
+                cs->ops->set_line_ctrl(cs, CS8);
+                cs->control_state = TIOCM_DTR|TIOCM_RTS;
+        }
+
+        cs->waiting = 1;
+        if (!gigaset_add_event(cs, &cs->at_state, EV_IF_LOCK,
+                               NULL, cmd, NULL)) {
+                cs->waiting = 0;
+                return -ENOMEM;
+        }
+
+        dbg(DEBUG_CMD, "scheduling IF_LOCK");
+        gigaset_schedule_event(cs);
+
+        wait_event(cs->waitqueue, !cs->waiting);
+
+        if (cs->cmd_result >= 0) {
+                *arg = cs->cmd_result;
+                return 0;
+        }
+
+        return cs->cmd_result;
+}
+
+static int if_version(struct cardstate *cs, unsigned arg[4])
+{
+        static const unsigned version[4] = GIG_VERSION;
+        static const unsigned compat[4] = GIG_COMPAT;
+        unsigned cmd = arg[0];
+
+        dbg(DEBUG_IF, "%u: if_version (%d)", cs->minor_index, cmd);
+
+        switch (cmd) {
+        case GIGVER_DRIVER:
+                memcpy(arg, version, sizeof version);
+                return 0;
+        case GIGVER_COMPAT:
+                memcpy(arg, compat, sizeof compat);
+                return 0;
+        case GIGVER_FWBASE:
+                cs->waiting = 1;
+                if (!gigaset_add_event(cs, &cs->at_state, EV_IF_VER,
+                                       NULL, 0, arg)) {
+                        cs->waiting = 0;
+                        return -ENOMEM;
+                }
+
+                dbg(DEBUG_CMD, "scheduling IF_VER");
+                gigaset_schedule_event(cs);
+
+                wait_event(cs->waitqueue, !cs->waiting);
+
+                if (cs->cmd_result >= 0)
+                        return 0;
+
+                return cs->cmd_result;
+        default:
+                return -EINVAL;
+        }
+}
+
+static int if_config(struct cardstate *cs, int *arg)
+{
+        dbg(DEBUG_IF, "%u: if_config (%d)", cs->minor_index, *arg);
+
+        if (*arg != 1)
+                return -EINVAL;
+
+        if (atomic_read(&cs->mstate) != MS_LOCKED)
+                return -EBUSY;
+
+        *arg = 0;
+        return gigaset_enterconfigmode(cs);
+}
+
+/*** the terminal driver ***/
+/* stolen from usbserial and some other tty drivers */
+
+static int  if_open(struct tty_struct *tty, struct file *filp);
+static void if_close(struct tty_struct *tty, struct file *filp);
+static int  if_ioctl(struct tty_struct *tty, struct file *file,
+                     unsigned int cmd, unsigned long arg);
+static int  if_write_room(struct tty_struct *tty);
+static int  if_chars_in_buffer(struct tty_struct *tty);
+static void if_throttle(struct tty_struct *tty);
+static void if_unthrottle(struct tty_struct *tty);
+static void if_set_termios(struct tty_struct *tty, struct termios *old);
+static int  if_tiocmget(struct tty_struct *tty, struct file *file);
+static int  if_tiocmset(struct tty_struct *tty, struct file *file,
+                        unsigned int set, unsigned int clear);
+static int  if_write(struct tty_struct *tty,
+                     const unsigned char *buf, int count);
+
+static struct tty_operations if_ops = {
+        .open =                 if_open,
+        .close =                if_close,
+        .ioctl =                if_ioctl,
+        .write =                if_write,
+        .write_room =           if_write_room,
+        .chars_in_buffer =      if_chars_in_buffer,
+        .set_termios =          if_set_termios,
+        .throttle =             if_throttle,
+        .unthrottle =           if_unthrottle,
+#if 0
+        .break_ctl =            serial_break,
+#endif
+        .tiocmget =             if_tiocmget,
+        .tiocmset =             if_tiocmset,
+};
+
+static int if_open(struct tty_struct *tty, struct file *filp)
+{
+        struct cardstate *cs;
+        unsigned long flags;
+
+        dbg(DEBUG_IF, "%d+%d: %s()", tty->driver->minor_start, tty->index,
+            __FUNCTION__);
+
+        tty->driver_data = NULL;
+
+        cs = gigaset_get_cs_by_tty(tty);
+        if (!cs)
+                return -ENODEV;
+
+        if (down_interruptible(&cs->sem))
+                return -ERESTARTSYS; // FIXME -EINTR?
+        tty->driver_data = cs;
+
+        ++cs->open_count;
+
+        if (cs->open_count == 1) {
+                spin_lock_irqsave(&cs->lock, flags);
+                cs->tty = tty;
+                spin_unlock_irqrestore(&cs->lock, flags);
+                tty->low_latency = 1; //FIXME test
+                //FIXME
+        }
+
+        up(&cs->sem);
+        return 0;
+}
+
+static void if_close(struct tty_struct *tty, struct file *filp)
+{
+        struct cardstate *cs;
+        unsigned long flags;
+
+        cs = (struct cardstate *) tty->driver_data;
+        if (!cs) {
+                err("cs==NULL in %s", __FUNCTION__);
+                return;
+        }
+
+        dbg(DEBUG_IF, "%u: %s()", cs->minor_index, __FUNCTION__);
+
+        down(&cs->sem);
+
+        if (!cs->open_count)
+                warn("%s: device not opened", __FUNCTION__);
+        else {
+                if (!--cs->open_count) {
+                        spin_lock_irqsave(&cs->lock, flags);
+                        cs->tty = NULL;
+                        spin_unlock_irqrestore(&cs->lock, flags);
+                        //FIXME
+                }
+        }
+
+        up(&cs->sem);
+}
+
+static int if_ioctl(struct tty_struct *tty, struct file *file,
+                    unsigned int cmd, unsigned long arg)
+{
+        struct cardstate *cs;
+        int retval = -ENODEV;
+        int int_arg;
+        unsigned char buf[6];
+        unsigned version[4];
+
+        cs = (struct cardstate *) tty->driver_data;
+        if (!cs) {
+                err("cs==NULL in %s", __FUNCTION__);
+                return -ENODEV;
+        }
+
+        dbg(DEBUG_IF, "%u: %s(0x%x)", cs->minor_index, __FUNCTION__, cmd);
+
+        if (down_interruptible(&cs->sem))
+                return -ERESTARTSYS; // FIXME -EINTR?
+
+        if (!cs->open_count)
+                warn("%s: device not opened", __FUNCTION__);
+        else {
+                retval = 0;
+                switch (cmd) {
+                case GIGASET_REDIR:
+                        retval = get_user(int_arg, (int __user *) arg);
+                        if (retval >= 0)
+                                retval = if_lock(cs, &int_arg);
+                        if (retval >= 0)
+                                retval = put_user(int_arg, (int __user *) arg);
+                        break;
+                case GIGASET_CONFIG:
+                        retval = get_user(int_arg, (int __user *) arg);
+                        if (retval >= 0)
+                                retval = if_config(cs, &int_arg);
+                        if (retval >= 0)
+                                retval = put_user(int_arg, (int __user *) arg);
+                        break;
+                case GIGASET_BRKCHARS:
+                        //FIXME test if MS_LOCKED
+                        gigaset_dbg_buffer(DEBUG_IF, "GIGASET_BRKCHARS",
+                                           6, (const unsigned char *) arg, 1);
+                        if (!atomic_read(&cs->connected)) {
+                                dbg(DEBUG_ANY, "can't communicate with unplugged device");
+                                retval = -ENODEV;
+                                break;
+                        }
+                        retval = copy_from_user(&buf,
+                                                (const unsigned char __user *) arg, 6)
+                                 ? -EFAULT : 0;
+                        if (retval >= 0)
+                                retval = cs->ops->brkchars(cs, buf);
+                        break;
+                case GIGASET_VERSION:
+                        retval = copy_from_user(version, (unsigned __user *) arg,
+                                                sizeof version) ? -EFAULT : 0;
+                        if (retval >= 0)
+                                retval = if_version(cs, version);
+                        if (retval >= 0)
+                                retval = copy_to_user((unsigned __user *) arg, version,
+                                                      sizeof version)
+                                         ? -EFAULT : 0;
+                        break;
+                default:
+                        dbg(DEBUG_ANY, "%s: arg not supported - 0x%04x",
+                            __FUNCTION__, cmd);
+                        retval = -ENOIOCTLCMD;
+                }
+        }
+
+        up(&cs->sem);
+
+        return retval;
+}
+
+static int if_tiocmget(struct tty_struct *tty, struct file *file)
+{
+        struct cardstate *cs;
+        int retval;
+
+        cs = (struct cardstate *) tty->driver_data;
+        if (!cs) {
+                err("cs==NULL in %s", __FUNCTION__);
+                return -ENODEV;
+        }
+
+        dbg(DEBUG_IF, "%u: %s()", cs->minor_index, __FUNCTION__);
+
+        if (down_interruptible(&cs->sem))
+                return -ERESTARTSYS; // FIXME -EINTR?
+
+        // FIXME read from device?
+        retval = cs->control_state & (TIOCM_RTS|TIOCM_DTR);
+
+        up(&cs->sem);
+
+        return retval;
+}
+
+static int if_tiocmset(struct tty_struct *tty, struct file *file,
+                       unsigned int set, unsigned int clear)
+{
+        struct cardstate *cs;
+        int retval;
+        unsigned mc;
+
+        cs = (struct cardstate *) tty->driver_data;
+        if (!cs) {
+                err("cs==NULL in %s", __FUNCTION__);
+                return -ENODEV;
+        }
+
+        dbg(DEBUG_IF,
+            "%u: %s(0x%x, 0x%x)", cs->minor_index, __FUNCTION__, set, clear);
+
+        if (down_interruptible(&cs->sem))
+                return -ERESTARTSYS; // FIXME -EINTR?
+
+        if (!atomic_read(&cs->connected)) {
+                dbg(DEBUG_ANY, "can't communicate with unplugged device");
+                retval = -ENODEV;
+        } else {
+                mc = (cs->control_state | set) & ~clear & (TIOCM_RTS|TIOCM_DTR);
+                retval = cs->ops->set_modem_ctrl(cs, cs->control_state, mc);
+                cs->control_state = mc;
+        }
+
+        up(&cs->sem);
+
+        return retval;
+}
+
+static int if_write(struct tty_struct *tty, const unsigned char *buf, int count)
+{
+        struct cardstate *cs;
+        int retval = -ENODEV;
+
+        cs = (struct cardstate *) tty->driver_data;
+        if (!cs) {
+                err("cs==NULL in %s", __FUNCTION__);
+                return -ENODEV;
+        }
+
+        dbg(DEBUG_IF, "%u: %s()", cs->minor_index, __FUNCTION__);
+
+        if (down_interruptible(&cs->sem))
+                return -ERESTARTSYS; // FIXME -EINTR?
+
+        if (!cs->open_count)
+                warn("%s: device not opened", __FUNCTION__);
+        else if (atomic_read(&cs->mstate) != MS_LOCKED) {
+                warn("can't write to unlocked device");
+                retval = -EBUSY;
+        } else if (!atomic_read(&cs->connected)) {
+                dbg(DEBUG_ANY, "can't write to unplugged device");
+                retval = -EBUSY; //FIXME
+        } else {
+                retval = cs->ops->write_cmd(cs, buf, count,
+                                            &cs->if_wake_tasklet);
+        }
+
+        up(&cs->sem);
+
+        return retval;
+}
+
+static int if_write_room(struct tty_struct *tty)
+{
+        struct cardstate *cs;
+        int retval = -ENODEV;
+
+        cs = (struct cardstate *) tty->driver_data;
+        if (!cs) {
+                err("cs==NULL in %s", __FUNCTION__);
+                return -ENODEV;
+        }
+
+        dbg(DEBUG_IF, "%u: %s()", cs->minor_index, __FUNCTION__);
+
+        if (down_interruptible(&cs->sem))
+                return -ERESTARTSYS; // FIXME -EINTR?
+
+        if (!cs->open_count)
+                warn("%s: device not opened", __FUNCTION__);
+        else if (atomic_read(&cs->mstate) != MS_LOCKED) {
+                warn("can't write to unlocked device");
+                retval = -EBUSY; //FIXME
+        } else if (!atomic_read(&cs->connected)) {
+                dbg(DEBUG_ANY, "can't write to unplugged device");
+                retval = -EBUSY; //FIXME
+        } else
+                retval = cs->ops->write_room(cs);
+
+        up(&cs->sem);
+
+        return retval;
+}
+
+static int if_chars_in_buffer(struct tty_struct *tty)
+{
+        struct cardstate *cs;
+        int retval = -ENODEV;
+
+        cs = (struct cardstate *) tty->driver_data;
+        if (!cs) {
+                err("cs==NULL in %s", __FUNCTION__);
+                return -ENODEV;
+        }
+
+        dbg(DEBUG_IF, "%u: %s()", cs->minor_index, __FUNCTION__);
+
+        if (down_interruptible(&cs->sem))
+                return -ERESTARTSYS; // FIXME -EINTR?
+
+        if (!cs->open_count)
+                warn("%s: device not opened", __FUNCTION__);
+        else if (atomic_read(&cs->mstate) != MS_LOCKED) {
+                warn("can't write to unlocked device");
+                retval = -EBUSY;
+        } else if (!atomic_read(&cs->connected)) {
+                dbg(DEBUG_ANY, "can't write to unplugged device");
+                retval = -EBUSY; //FIXME
+        } else
+                retval = cs->ops->chars_in_buffer(cs);
+
+        up(&cs->sem);
+
+        return retval;
+}
+
+static void if_throttle(struct tty_struct *tty)
+{
+        struct cardstate *cs;
+
+        cs = (struct cardstate *) tty->driver_data;
+        if (!cs) {
+                err("cs==NULL in %s", __FUNCTION__);
+                return;
+        }
+
+        dbg(DEBUG_IF, "%u: %s()", cs->minor_index, __FUNCTION__);
+
+        down(&cs->sem);
+
+        if (!cs->open_count)
+                warn("%s: device not opened", __FUNCTION__);
+        else {
+                //FIXME
+        }
+
+        up(&cs->sem);
+}
+
+static void if_unthrottle(struct tty_struct *tty)
+{
+        struct cardstate *cs;
+
+        cs = (struct cardstate *) tty->driver_data;
+        if (!cs) {
+                err("cs==NULL in %s", __FUNCTION__);
+                return;
+        }
+
+        dbg(DEBUG_IF, "%u: %s()", cs->minor_index, __FUNCTION__);
+
+        down(&cs->sem);
+
+        if (!cs->open_count)
+                warn("%s: device not opened", __FUNCTION__);
+        else {
+                //FIXME
+        }
+
+        up(&cs->sem);
+}
+
+static void if_set_termios(struct tty_struct *tty, struct termios *old)
+{
+        struct cardstate *cs;
+        unsigned int iflag;
+        unsigned int cflag;
+        unsigned int old_cflag;
+        unsigned int control_state, new_state;
+
+        cs = (struct cardstate *) tty->driver_data;
+        if (!cs) {
+                err("cs==NULL in %s", __FUNCTION__);
+                return;
+        }
+
+        dbg(DEBUG_IF, "%u: %s()", cs->minor_index, __FUNCTION__);
+
+        down(&cs->sem);
+
+        if (!cs->open_count) {
+                warn("%s: device not opened", __FUNCTION__);
+                goto out;
+        }
+
+        if (!atomic_read(&cs->connected)) {
+                dbg(DEBUG_ANY, "can't communicate with unplugged device");
+                goto out;
+        }
+
+        // stolen from mct_u232.c
+        iflag = tty->termios->c_iflag;
+        cflag = tty->termios->c_cflag;
+        old_cflag = old ? old->c_cflag : cflag; //FIXME?
+        dbg(DEBUG_IF, "%u: iflag %x cflag %x old %x", cs->minor_index,
+            iflag, cflag, old_cflag);
+
+        /* get a local copy of the current port settings */
+        control_state = cs->control_state;
+
+        /*
+         * Update baud rate.
+         * Do not attempt to cache old rates and skip settings,
+         * disconnects screw such tricks up completely.
+         * Premature optimization is the root of all evil.
+         */
+
+        /* reassert DTR and (maybe) RTS on transition from B0 */
+        if ((old_cflag & CBAUD) == B0) {
+                new_state = control_state | TIOCM_DTR;
+                /* don't set RTS if using hardware flow control */
+                if (!(old_cflag & CRTSCTS))
+                        new_state |= TIOCM_RTS;
+                dbg(DEBUG_IF, "%u: from B0 - set DTR%s", cs->minor_index,
+                    (new_state & TIOCM_RTS) ? " only" : "/RTS");
+                cs->ops->set_modem_ctrl(cs, control_state, new_state);
+                control_state = new_state;
+        }
+
+        cs->ops->baud_rate(cs, cflag & CBAUD);
+
+        if ((cflag & CBAUD) == B0) {
+                /* Drop RTS and DTR */
+                dbg(DEBUG_IF, "%u: to B0 - drop DTR/RTS", cs->minor_index);
+                new_state = control_state & ~(TIOCM_DTR | TIOCM_RTS);
+                cs->ops->set_modem_ctrl(cs, control_state, new_state);
+                control_state = new_state;
+        }
+
+        /*
+         * Update line control register (LCR)
+         */
+
+        cs->ops->set_line_ctrl(cs, cflag);
+
+#if 0
+        //FIXME this hangs M101 [ts 2005-03-09]
+        //FIXME do we need this?
+        /*
+         * Set flow control: well, I do not really now how to handle DTR/RTS.
+         * Just do what we have seen with SniffUSB on Win98.
+         */
+        /* Drop DTR/RTS if no flow control otherwise assert */
+        dbg(DEBUG_IF, "%u: control_state %x", cs->minor_index, control_state);
+        new_state = control_state;
+        if ((iflag & IXOFF) || (iflag & IXON) || (cflag & CRTSCTS))
+                new_state |= TIOCM_DTR | TIOCM_RTS;
+        else
+                new_state &= ~(TIOCM_DTR | TIOCM_RTS);
+        if (new_state != control_state) {
+                dbg(DEBUG_IF, "%u: new_state %x", cs->minor_index, new_state);
+                gigaset_set_modem_ctrl(cs, control_state, new_state); // FIXME: mct_u232.c sets the old state here. is this a bug?
+                control_state = new_state;
+        }
+#endif
+
+        /* save off the modified port settings */
+        cs->control_state = control_state;
+
+out:
+        up(&cs->sem);
+}
+
+
+/* wakeup tasklet for the write operation */
+static void if_wake(unsigned long data)
+{
+        struct cardstate *cs = (struct cardstate *) data;
+        struct tty_struct *tty;
+
+        tty = cs->tty;
+        if (!tty)
+                return;
+
+        if ((tty->flags & (1 << TTY_DO_WRITE_WAKEUP)) &&
+            tty->ldisc.write_wakeup) {
+                dbg(DEBUG_IF, "write wakeup call");
+                tty->ldisc.write_wakeup(tty);
+        }
+
+        wake_up_interruptible(&tty->write_wait);
+}
+
+/*** interface to common ***/
+
+void gigaset_if_init(struct cardstate *cs)
+{
+        struct gigaset_driver *drv;
+
+        drv = cs->driver;
+        if (!drv->have_tty)
+                return;
+
+        tasklet_init(&cs->if_wake_tasklet, &if_wake, (unsigned long) cs);
+        tty_register_device(drv->tty, cs->minor_index, NULL);
+}
+
+void gigaset_if_free(struct cardstate *cs)
+{
+        struct gigaset_driver *drv;
+
+        drv = cs->driver;
+        if (!drv->have_tty)
+                return;
+
+        tasklet_disable(&cs->if_wake_tasklet);
+        tasklet_kill(&cs->if_wake_tasklet);
+        tty_unregister_device(drv->tty, cs->minor_index);
+}
+
+void gigaset_if_receive(struct cardstate *cs,
+                        unsigned char *buffer, size_t len)
+{
+        unsigned long flags;
+        struct tty_struct *tty;
+
+        spin_lock_irqsave(&cs->lock, flags);
+        if ((tty = cs->tty) == NULL)
+                dbg(DEBUG_ANY, "receive on closed device");
+        else {
+                tty_buffer_request_room(tty, len);
+                tty_insert_flip_string(tty, buffer, len);
+                tty_flip_buffer_push(tty);
+        }
+        spin_unlock_irqrestore(&cs->lock, flags);
+}
+EXPORT_SYMBOL_GPL(gigaset_if_receive);
+
+/* gigaset_if_initdriver
+ * Initialize tty interface.
+ * parameters:
+ *      drv             Driver
+ *      procname        Name of the driver (e.g. for /proc/tty/drivers)
+ *      devname         Name of the device files (prefix without minor number)
+ *      devfsname       Devfs name of the device files without %d
+ */
+void gigaset_if_initdriver(struct gigaset_driver *drv, const char *procname,
+                           const char *devname, const char *devfsname)
+{
+        unsigned minors = drv->minors;
+        int ret;
+        struct tty_driver *tty;
+
+        drv->have_tty = 0;
+
+        if ((drv->tty = alloc_tty_driver(minors)) == NULL)
+                goto enomem;
+        tty = drv->tty;
+
+        tty->magic =            TTY_DRIVER_MAGIC,
+        tty->major =            GIG_MAJOR,
+        tty->type =             TTY_DRIVER_TYPE_SERIAL,
+        tty->subtype =          SERIAL_TYPE_NORMAL,
+        tty->flags =            TTY_DRIVER_REAL_RAW | TTY_DRIVER_NO_DEVFS,
+
+        tty->driver_name =      procname;
+        tty->name =             devname;
+        tty->minor_start =      drv->minor;
+        tty->num =              drv->minors;
+
+        tty->owner =            THIS_MODULE;
+        tty->devfs_name =       devfsname;
+
+        tty->init_termios          = tty_std_termios; //FIXME
+        tty->init_termios.c_cflag  = B9600 | CS8 | CREAD | HUPCL | CLOCAL; //FIXME
+        tty_set_operations(tty, &if_ops);
+
+        ret = tty_register_driver(tty);
+        if (ret < 0) {
+                warn("failed to register tty driver (error %d)", ret);
+                goto error;
+        }
+        dbg(DEBUG_IF, "tty driver initialized");
+        drv->have_tty = 1;
+        return;
+
+enomem:
+        warn("could not allocate tty structures");
+error:
+        if (drv->tty)
+                put_tty_driver(drv->tty);
+}
+
+void gigaset_if_freedriver(struct gigaset_driver *drv)
+{
+        if (!drv->have_tty)
+                return;
+
+        drv->have_tty = 0;
+        tty_unregister_driver(drv->tty);
+        put_tty_driver(drv->tty);
+}