4 files changed, 40 insertions, 19 deletions

diff --git a/drivers/char/amiserial.c b/drivers/char/amiserial.c
index 1dc4259213a..777bc499bbb 100644
--- a/drivers/char/amiserial.c
+++ b/drivers/char/amiserial.c
@@ -861,13 +861,18 @@ static void change_speed(struct async_struct *info,
 
 static void rs_put_char(struct tty_struct *tty, unsigned char ch)
 {
-	struct async_struct *info = (struct async_struct *)tty->driver_data;
+	struct async_struct *info;
 	unsigned long flags;
 
+	if (!tty)
+		return;
+
+	info = tty->driver_data;
+
 	if (serial_paranoia_check(info, tty->name, "rs_put_char"))
 		return;
 
-	if (!tty || !info->xmit.buf)
+	if (!info->xmit.buf)
 		return;
 
 	local_irq_save(flags);
@@ -910,13 +915,18 @@ static void rs_flush_chars(struct tty_struct *tty)
 static int rs_write(struct tty_struct * tty, const unsigned char *buf, int count)
 {
 	int	c, ret = 0;
-	struct async_struct *info = (struct async_struct *)tty->driver_data;
+	struct async_struct *info;
 	unsigned long flags;
 
+	if (!tty)
+		return 0;
+
+	info = tty->driver_data;
+
 	if (serial_paranoia_check(info, tty->name, "rs_write"))
 		return 0;
 
-	if (!tty || !info->xmit.buf || !tmp_buf)
+	if (!info->xmit.buf || !tmp_buf)
 		return 0;
 
 	local_save_flags(flags);
diff --git a/drivers/char/n_hdlc.c b/drivers/char/n_hdlc.c
index b3dbff1cf96..5079beda69b 100644
--- a/drivers/char/n_hdlc.c
+++ b/drivers/char/n_hdlc.c
@@ -960,7 +960,7 @@ static char hdlc_unregister_fail[] __exitdata =
 static void __exit n_hdlc_exit(void)
 {
 	/* Release tty registration of line discipline */
-	int status = tty_register_ldisc(N_HDLC, NULL);
+	int status = tty_unregister_ldisc(N_HDLC);
 
 	if (status)
 		printk(hdlc_unregister_fail, status);
diff --git a/drivers/char/n_r3964.c b/drivers/char/n_r3964.c
index 3883073ab48..2291a87e8ad 100644
--- a/drivers/char/n_r3964.c
+++ b/drivers/char/n_r3964.c
@@ -200,7 +200,7 @@ static void __exit r3964_exit(void)
    
    TRACE_M ("cleanup_module()");
 
-   status=tty_register_ldisc(N_R3964, NULL);
+   status=tty_unregister_ldisc(N_R3964);
    
    if(status!=0)
    {
diff --git a/drivers/char/tty_io.c b/drivers/char/tty_io.c
index 31831030f73..cc4b43bad70 100644
--- a/drivers/char/tty_io.c
+++ b/drivers/char/tty_io.c
@@ -251,7 +251,7 @@ static void tty_set_termios_ldisc(struct tty_struct *tty, int num)
  
 static DEFINE_SPINLOCK(tty_ldisc_lock);
 static DECLARE_WAIT_QUEUE_HEAD(tty_ldisc_wait);
-static struct tty_ldisc tty_ldiscs[NR_LDISCS];	/* line disc dispatch table	*/
+static struct tty_ldisc tty_ldiscs[NR_LDISCS];	/* line disc dispatch table */
 
 int tty_register_ldisc(int disc, struct tty_ldisc *new_ldisc)
 {
@@ -262,24 +262,35 @@ int tty_register_ldisc(int disc, struct tty_ldisc *new_ldisc)
 		return -EINVAL;
 	
 	spin_lock_irqsave(&tty_ldisc_lock, flags);
-	if (new_ldisc) {
-		tty_ldiscs[disc] = *new_ldisc;
-		tty_ldiscs[disc].num = disc;
-		tty_ldiscs[disc].flags |= LDISC_FLAG_DEFINED;
-		tty_ldiscs[disc].refcount = 0;
-	} else {
-		if(tty_ldiscs[disc].refcount)
-			ret = -EBUSY;
-		else
-			tty_ldiscs[disc].flags &= ~LDISC_FLAG_DEFINED;
-	}
+	tty_ldiscs[disc] = *new_ldisc;
+	tty_ldiscs[disc].num = disc;
+	tty_ldiscs[disc].flags |= LDISC_FLAG_DEFINED;
+	tty_ldiscs[disc].refcount = 0;
 	spin_unlock_irqrestore(&tty_ldisc_lock, flags);
 	
 	return ret;
 }
-
 EXPORT_SYMBOL(tty_register_ldisc);
 
+int tty_unregister_ldisc(int disc)
+{
+	unsigned long flags;
+	int ret = 0;
+
+	if (disc < N_TTY || disc >= NR_LDISCS)
+		return -EINVAL;
+
+	spin_lock_irqsave(&tty_ldisc_lock, flags);
+	if (tty_ldiscs[disc].refcount)
+		ret = -EBUSY;
+	else
+		tty_ldiscs[disc].flags &= ~LDISC_FLAG_DEFINED;
+	spin_unlock_irqrestore(&tty_ldisc_lock, flags);
+
+	return ret;
+}
+EXPORT_SYMBOL(tty_unregister_ldisc);
+
 struct tty_ldisc *tty_ldisc_get(int disc)
 {
 	unsigned long flags;