15 files changed, 251 insertions, 158 deletions

diff --git a/drivers/char/cyclades.c b/drivers/char/cyclades.c
index 6bff9d87dc57..a957dbcc5a46 100644
--- a/drivers/char/cyclades.c
+++ b/drivers/char/cyclades.c
@@ -5246,7 +5246,8 @@ cyclades_get_proc_info(char *buf, char **start, off_t offset, int length,
                                         HZ, info->idle_stats.recv_bytes,
                                         (cur_jifs - info->idle_stats.recv_idle)/
                                         HZ, info->idle_stats.overruns,
-                                        (long)info->tty->ldisc.num);
+                                        /* FIXME: double check locking */
+                                        (long)info->tty->ldisc.ops->num);
                         else
                                 size = sprintf(buf + len, "%3d %8lu %10lu %8lu "
                                         "%10lu %8lu %9lu %6ld\n",
diff --git a/drivers/char/epca.c b/drivers/char/epca.c
index 60a4df7dac12..aa8e19f44b45 100644
--- a/drivers/char/epca.c
+++ b/drivers/char/epca.c
@@ -2262,8 +2262,8 @@ static int pc_ioctl(struct tty_struct *tty, struct file *file,
                         tty_wait_until_sent(tty, 0);
                 } else {
                         /* ldisc lock already held in ioctl */
-                        if (tty->ldisc.flush_buffer)
-                                tty->ldisc.flush_buffer(tty);
+                        if (tty->ldisc.ops->flush_buffer)
+                                tty->ldisc.ops->flush_buffer(tty);
                 }
                 unlock_kernel();
                 /* Fall Thru */
diff --git a/drivers/char/ip2/i2lib.c b/drivers/char/ip2/i2lib.c
index 938879cc7bcc..0061e18aff60 100644
--- a/drivers/char/ip2/i2lib.c
+++ b/drivers/char/ip2/i2lib.c
@@ -868,11 +868,11 @@ i2Input(i2ChanStrPtr pCh)
                 amountToMove = count;
         }
         // Move the first block
-        pCh->pTTY->ldisc.receive_buf( pCh->pTTY, 
+        pCh->pTTY->ldisc.ops->receive_buf( pCh->pTTY,
                  &(pCh->Ibuf[stripIndex]), NULL, amountToMove );
         // If we needed to wrap, do the second data move
         if (count > amountToMove) {
-                pCh->pTTY->ldisc.receive_buf( pCh->pTTY, 
+                pCh->pTTY->ldisc.ops->receive_buf( pCh->pTTY,
                  pCh->Ibuf, NULL, count - amountToMove );
         }
         // Bump and wrap the stripIndex all at once by the amount of data read. This
diff --git a/drivers/char/ip2/ip2main.c b/drivers/char/ip2/ip2main.c
index 9a2394cda943..5dc74404058f 100644
--- a/drivers/char/ip2/ip2main.c
+++ b/drivers/char/ip2/ip2main.c
@@ -1289,11 +1289,12 @@ static void do_input(struct work_struct *work)
 // code duplicated from n_tty (ldisc)
 static inline void  isig(int sig, struct tty_struct *tty, int flush)
 {
+        /* FIXME: This is completely bogus */
         if (tty->pgrp)
                 kill_pgrp(tty->pgrp, sig, 1);
         if (flush || !L_NOFLSH(tty)) {
-                if ( tty->ldisc.flush_buffer )  
-                        tty->ldisc.flush_buffer(tty);
+                if ( tty->ldisc.ops->flush_buffer )  
+                        tty->ldisc.ops->flush_buffer(tty);
                 i2InputFlush( tty->driver_data );
         }
 }
@@ -1342,7 +1343,7 @@ static void do_status(struct work_struct *work)
                 }
                 tmp = pCh->pTTY->real_raw;
                 pCh->pTTY->real_raw = 0;
-                pCh->pTTY->ldisc.receive_buf( pCh->pTTY, &brkc, &brkf, 1 );
+                pCh->pTTY->ldisc->ops.receive_buf( pCh->pTTY, &brkc, &brkf, 1 );
                 pCh->pTTY->real_raw = tmp;
         }
 #endif /* NEVER_HAPPENS_AS_SETUP_XXX */
diff --git a/drivers/char/n_hdlc.c b/drivers/char/n_hdlc.c
index a35bfd7ee80e..ed4e03333ab4 100644
--- a/drivers/char/n_hdlc.c
+++ b/drivers/char/n_hdlc.c
@@ -199,7 +199,7 @@ static void n_hdlc_tty_wakeup(struct tty_struct *tty);
 #define tty2n_hdlc(tty) ((struct n_hdlc *) ((tty)->disc_data))
 #define n_hdlc2tty(n_hdlc)      ((n_hdlc)->tty)
 
-static struct tty_ldisc n_hdlc_ldisc = {
+static struct tty_ldisc_ops n_hdlc_ldisc = {
         .owner          = THIS_MODULE,
         .magic          = TTY_LDISC_MAGIC,
         .name           = "hdlc",
@@ -342,8 +342,8 @@ static int n_hdlc_tty_open (struct tty_struct *tty)
 #endif
         
         /* Flush any pending characters in the driver and discipline. */
-        if (tty->ldisc.flush_buffer)
-                tty->ldisc.flush_buffer(tty);
+        if (tty->ldisc.ops->flush_buffer)
+                tty->ldisc.ops->flush_buffer(tty);
 
         tty_driver_flush_buffer(tty);
                 
diff --git a/drivers/char/n_r3964.c b/drivers/char/n_r3964.c
index 902169062332..ae377aa473ba 100644
--- a/drivers/char/n_r3964.c
+++ b/drivers/char/n_r3964.c
@@ -143,7 +143,7 @@ static unsigned int r3964_poll(struct tty_struct *tty, struct file *file,
 static void r3964_receive_buf(struct tty_struct *tty, const unsigned char *cp,
                 char *fp, int count);
 
-static struct tty_ldisc tty_ldisc_N_R3964 = {
+static struct tty_ldisc_ops tty_ldisc_N_R3964 = {
         .owner = THIS_MODULE,
         .magic = TTY_LDISC_MAGIC,
         .name = "R3964",
diff --git a/drivers/char/n_tty.c b/drivers/char/n_tty.c
index 8096389b0dc2..708c2b1dbe51 100644
--- a/drivers/char/n_tty.c
+++ b/drivers/char/n_tty.c
@@ -1573,7 +1573,7 @@ static unsigned int normal_poll(struct tty_struct *tty, struct file *file,
         return mask;
 }
 
-struct tty_ldisc tty_ldisc_N_TTY = {
+struct tty_ldisc_ops tty_ldisc_N_TTY = {
         .magic           = TTY_LDISC_MAGIC,
         .name            = "n_tty",
         .open            = n_tty_open,
diff --git a/drivers/char/pcmcia/synclink_cs.c b/drivers/char/pcmcia/synclink_cs.c
index 1dd0e992c83d..95743e2682fe 100644
--- a/drivers/char/pcmcia/synclink_cs.c
+++ b/drivers/char/pcmcia/synclink_cs.c
@@ -514,8 +514,8 @@ static void ldisc_receive_buf(struct tty_struct *tty,
                 return;
         ld = tty_ldisc_ref(tty);
         if (ld) {
-                if (ld->receive_buf)
-                        ld->receive_buf(tty, data, flags, count);
+                if (ld->ops->receive_buf)
+                        ld->ops->receive_buf(tty, data, flags, count);
                 tty_ldisc_deref(ld);
         }
 }
diff --git a/drivers/char/pty.c b/drivers/char/pty.c
index 0a05c038ae6f..76b27932d229 100644
--- a/drivers/char/pty.c
+++ b/drivers/char/pty.c
@@ -111,7 +111,7 @@ static int pty_write(struct tty_struct * tty, const unsigned char *buf, int coun
         c = to->receive_room;
         if (c > count)
                 c = count;
-        to->ldisc.receive_buf(to, buf, NULL, c);
+        to->ldisc.ops->receive_buf(to, buf, NULL, c);
         
         return c;
 }
@@ -149,11 +149,11 @@ static int pty_chars_in_buffer(struct tty_struct *tty)
         int count;
 
         /* We should get the line discipline lock for "tty->link" */
-        if (!to || !to->ldisc.chars_in_buffer)
+        if (!to || !to->ldisc.ops->chars_in_buffer)
                 return 0;
 
         /* The ldisc must report 0 if no characters available to be read */
-        count = to->ldisc.chars_in_buffer(to);
+        count = to->ldisc.ops->chars_in_buffer(to);
 
         if (tty->driver->subtype == PTY_TYPE_SLAVE) return count;
 
@@ -186,8 +186,8 @@ static void pty_flush_buffer(struct tty_struct *tty)
         if (!to)
                 return;
         
-        if (to->ldisc.flush_buffer)
-                to->ldisc.flush_buffer(to);
+        if (to->ldisc.ops->flush_buffer)
+                to->ldisc.ops->flush_buffer(to);
         
         if (to->packet) {
                 spin_lock_irqsave(&tty->ctrl_lock, flags);
diff --git a/drivers/char/selection.c b/drivers/char/selection.c
index d63f5ccc29e6..2978a49a172b 100644
--- a/drivers/char/selection.c
+++ b/drivers/char/selection.c
@@ -327,7 +327,8 @@ int paste_selection(struct tty_struct *tty)
                 }
                 count = sel_buffer_lth - pasted;
                 count = min(count, tty->receive_room);
-                tty->ldisc.receive_buf(tty, sel_buffer + pasted, NULL, count);
+                tty->ldisc.ops->receive_buf(tty, sel_buffer + pasted,
+                                                                NULL, count);
                 pasted += count;
         }
         remove_wait_queue(&vc->paste_wait, &wait);
diff --git a/drivers/char/synclink.c b/drivers/char/synclink.c
index ac5080df2565..5e4b2e638d0c 100644
--- a/drivers/char/synclink.c
+++ b/drivers/char/synclink.c
@@ -975,8 +975,8 @@ static void ldisc_receive_buf(struct tty_struct *tty,
                 return;
         ld = tty_ldisc_ref(tty);
         if (ld) {
-                if (ld->receive_buf)
-                        ld->receive_buf(tty, data, flags, count);
+                if (ld->ops->receive_buf)
+                        ld->ops->receive_buf(tty, data, flags, count);
                 tty_ldisc_deref(ld);
         }
 }
diff --git a/drivers/char/synclink_gt.c b/drivers/char/synclink_gt.c
index 55c1653be00c..e473778cd6fa 100644
--- a/drivers/char/synclink_gt.c
+++ b/drivers/char/synclink_gt.c
@@ -641,8 +641,8 @@ static void ldisc_receive_buf(struct tty_struct *tty,
                 return;
         ld = tty_ldisc_ref(tty);
         if (ld) {
-                if (ld->receive_buf)
-                        ld->receive_buf(tty, data, flags, count);
+                if (ld->ops->receive_buf)
+                        ld->ops->receive_buf(tty, data, flags, count);
                 tty_ldisc_deref(ld);
         }
 }
diff --git a/drivers/char/synclinkmp.c b/drivers/char/synclinkmp.c
index bec54866e0bb..5341b5aaf8bc 100644
--- a/drivers/char/synclinkmp.c
+++ b/drivers/char/synclinkmp.c
@@ -712,8 +712,8 @@ static void ldisc_receive_buf(struct tty_struct *tty,
                 return;
         ld = tty_ldisc_ref(tty);
         if (ld) {
-                if (ld->receive_buf)
-                        ld->receive_buf(tty, data, flags, count);
+                if (ld->ops->receive_buf)
+                        ld->ops->receive_buf(tty, data, flags, count);
                 tty_ldisc_deref(ld);
         }
 }
diff --git a/drivers/char/tty_io.c b/drivers/char/tty_io.c
index 047a17339f83..54c4ada460ee 100644
--- a/drivers/char/tty_io.c
+++ b/drivers/char/tty_io.c
@@ -95,8 +95,9 @@
 #include <linux/wait.h>
 #include <linux/bitops.h>
 #include <linux/delay.h>
+#include <linux/seq_file.h>
 
-#include <asm/uaccess.h>
+#include <linux/uaccess.h>
 #include <asm/system.h>
 
 #include <linux/kbd_kern.h>
@@ -682,7 +683,7 @@ 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);
 /* Line disc dispatch table */
-static struct tty_ldisc tty_ldiscs[NR_LDISCS];
+static struct tty_ldisc_ops *tty_ldiscs[NR_LDISCS];
 
 /**
  *      tty_register_ldisc      -       install a line discipline
@@ -697,7 +698,7 @@ static struct tty_ldisc tty_ldiscs[NR_LDISCS];
  *              takes tty_ldisc_lock to guard against ldisc races
  */
 
-int tty_register_ldisc(int disc, struct tty_ldisc *new_ldisc)
+int tty_register_ldisc(int disc, struct tty_ldisc_ops *new_ldisc)
 {
         unsigned long flags;
         int ret = 0;
@@ -706,10 +707,9 @@ int tty_register_ldisc(int disc, struct tty_ldisc *new_ldisc)
                 return -EINVAL;
 
         spin_lock_irqsave(&tty_ldisc_lock, flags);
-        tty_ldiscs[disc] = *new_ldisc;
-        tty_ldiscs[disc].num = disc;
-        tty_ldiscs[disc].flags |= LDISC_FLAG_DEFINED;
-        tty_ldiscs[disc].refcount = 0;
+        tty_ldiscs[disc] = new_ldisc;
+        new_ldisc->num = disc;
+        new_ldisc->refcount = 0;
         spin_unlock_irqrestore(&tty_ldisc_lock, flags);
 
         return ret;
@@ -737,19 +737,56 @@ int tty_unregister_ldisc(int disc)
                 return -EINVAL;
 
         spin_lock_irqsave(&tty_ldisc_lock, flags);
-        if (tty_ldiscs[disc].refcount)
+        if (tty_ldiscs[disc]->refcount)
                 ret = -EBUSY;
         else
-                tty_ldiscs[disc].flags &= ~LDISC_FLAG_DEFINED;
+                tty_ldiscs[disc] = NULL;
         spin_unlock_irqrestore(&tty_ldisc_lock, flags);
 
         return ret;
 }
 EXPORT_SYMBOL(tty_unregister_ldisc);
 
+
+/**
+ *      tty_ldisc_try_get       -       try and reference an ldisc
+ *      @disc: ldisc number
+ *      @ld: tty ldisc structure to complete
+ *
+ *      Attempt to open and lock a line discipline into place. Return
+ *      the line discipline refcounted and assigned in ld. On an error
+ *      report the error code back
+ */
+
+static int tty_ldisc_try_get(int disc, struct tty_ldisc *ld)
+{
+        unsigned long flags;
+        struct tty_ldisc_ops *ldops;
+        int err = -EINVAL;
+        
+        spin_lock_irqsave(&tty_ldisc_lock, flags);
+        ld->ops = NULL;
+        ldops = tty_ldiscs[disc];
+        /* Check the entry is defined */
+        if (ldops) {
+                /* If the module is being unloaded we can't use it */
+                if (!try_module_get(ldops->owner))
+                        err = -EAGAIN;
+                else {
+                        /* lock it */
+                        ldops->refcount++;
+                        ld->ops = ldops;
+                        err = 0;
+                }
+        }
+        spin_unlock_irqrestore(&tty_ldisc_lock, flags);
+        return err;
+}
+
 /**
  *      tty_ldisc_get           -       take a reference to an ldisc
  *      @disc: ldisc number
+ *      @ld: tty line discipline structure to use
  *
  *      Takes a reference to a line discipline. Deals with refcounts and
  *      module locking counts. Returns NULL if the discipline is not available.
@@ -760,32 +797,20 @@ EXPORT_SYMBOL(tty_unregister_ldisc);
  *              takes tty_ldisc_lock to guard against ldisc races
  */
 
-struct tty_ldisc *tty_ldisc_get(int disc)
+static int tty_ldisc_get(int disc, struct tty_ldisc *ld)
 {
-        unsigned long flags;
-        struct tty_ldisc *ld;
+        int err;
 
         if (disc < N_TTY || disc >= NR_LDISCS)
-                return NULL;
-
-        spin_lock_irqsave(&tty_ldisc_lock, flags);
-
-        ld = &tty_ldiscs[disc];
-        /* Check the entry is defined */
-        if (ld->flags & LDISC_FLAG_DEFINED) {
-                /* If the module is being unloaded we can't use it */
-                if (!try_module_get(ld->owner))
-                        ld = NULL;
-                else /* lock it */
-                        ld->refcount++;
-        } else
-                ld = NULL;
-        spin_unlock_irqrestore(&tty_ldisc_lock, flags);
-        return ld;
+                return -EINVAL;
+        err = tty_ldisc_try_get(disc, ld);
+        if (err == -EAGAIN) {
+                request_module("tty-ldisc-%d", disc);
+                err = tty_ldisc_try_get(disc, ld);
+        }
+        return err;
 }
 
-EXPORT_SYMBOL_GPL(tty_ldisc_get);
-
 /**
  *      tty_ldisc_put           -       drop ldisc reference
  *      @disc: ldisc number
@@ -797,22 +822,67 @@ EXPORT_SYMBOL_GPL(tty_ldisc_get);
  *              takes tty_ldisc_lock to guard against ldisc races
  */
 
-void tty_ldisc_put(int disc)
+static void tty_ldisc_put(struct tty_ldisc_ops *ld)
 {
-        struct tty_ldisc *ld;
         unsigned long flags;
+        int disc = ld->num;
 
         BUG_ON(disc < N_TTY || disc >= NR_LDISCS);
 
         spin_lock_irqsave(&tty_ldisc_lock, flags);
-        ld = &tty_ldiscs[disc];
+        ld = tty_ldiscs[disc];
         BUG_ON(ld->refcount == 0);
         ld->refcount--;
         module_put(ld->owner);
         spin_unlock_irqrestore(&tty_ldisc_lock, flags);
 }
 
-EXPORT_SYMBOL_GPL(tty_ldisc_put);
+static void * tty_ldiscs_seq_start(struct seq_file *m, loff_t *pos)
+{
+        return (*pos < NR_LDISCS) ? pos : NULL;
+}
+
+static void * tty_ldiscs_seq_next(struct seq_file *m, void *v, loff_t *pos)
+{
+        (*pos)++;
+        return (*pos < NR_LDISCS) ? pos : NULL;
+}
+
+static void tty_ldiscs_seq_stop(struct seq_file *m, void *v)
+{
+}
+
+static int tty_ldiscs_seq_show(struct seq_file *m, void *v)
+{
+        int i = *(loff_t *)v;
+        struct tty_ldisc ld;
+        
+        if (tty_ldisc_get(i, &ld) < 0)
+                return 0;
+        seq_printf(m, "%-10s %2d\n", ld.ops->name ? ld.ops->name : "???", i);
+        tty_ldisc_put(ld.ops);
+        return 0;
+}
+
+static const struct seq_operations tty_ldiscs_seq_ops = {
+        .start  = tty_ldiscs_seq_start,
+        .next   = tty_ldiscs_seq_next,
+        .stop   = tty_ldiscs_seq_stop,
+        .show   = tty_ldiscs_seq_show,
+};
+
+static int proc_tty_ldiscs_open(struct inode *inode, struct file *file)
+{
+        return seq_open(file, &tty_ldiscs_seq_ops);
+}
+
+const struct file_operations tty_ldiscs_proc_fops = {
+        .owner          = THIS_MODULE,
+        .open           = proc_tty_ldiscs_open,
+        .read           = seq_read,
+        .llseek         = seq_lseek,
+        .release        = seq_release,
+};
 
 /**
  *      tty_ldisc_assign        -       set ldisc on a tty
@@ -829,8 +899,8 @@ EXPORT_SYMBOL_GPL(tty_ldisc_put);
 
 static void tty_ldisc_assign(struct tty_struct *tty, struct tty_ldisc *ld)
 {
+        ld->refcount = 0;
         tty->ldisc = *ld;
-        tty->ldisc.refcount = 0;
 }
 
 /**
@@ -954,6 +1024,41 @@ static void tty_ldisc_enable(struct tty_struct *tty)
 }
 
 /**
+ *      tty_ldisc_restore       -       helper for tty ldisc change
+ *      @tty: tty to recover
+ *      @old: previous ldisc
+ *
+ *      Restore the previous line discipline or N_TTY when a line discipline
+ *      change fails due to an open error
+ */
+
+static void tty_ldisc_restore(struct tty_struct *tty, struct tty_ldisc *old)
+{
+        char buf[64];
+        struct tty_ldisc new_ldisc;
+
+        /* There is an outstanding reference here so this is safe */
+        tty_ldisc_get(old->ops->num, old);
+        tty_ldisc_assign(tty, old);
+        tty_set_termios_ldisc(tty, old->ops->num);
+        if (old->ops->open && (old->ops->open(tty) < 0)) {
+                tty_ldisc_put(old->ops);
+                /* This driver is always present */
+                if (tty_ldisc_get(N_TTY, &new_ldisc) < 0)
+                        panic("n_tty: get");
+                tty_ldisc_assign(tty, &new_ldisc);
+                tty_set_termios_ldisc(tty, N_TTY);
+                if (new_ldisc.ops->open) {
+                        int r = new_ldisc.ops->open(tty);
+                                if (r < 0)
+                                panic("Couldn't open N_TTY ldisc for "
+                                      "%s --- error %d.",
+                                      tty_name(tty, buf), r);
+                }
+        }
+}
+
+/**
  *      tty_set_ldisc           -       set line discipline
  *      @tty: the terminal to set
  *      @ldisc: the line discipline
@@ -967,28 +1072,18 @@ static void tty_ldisc_enable(struct tty_struct *tty)
 
 static int tty_set_ldisc(struct tty_struct *tty, int ldisc)
 {
-        int retval = 0;
-        struct tty_ldisc o_ldisc;
-        char buf[64];
+        int retval;
+        struct tty_ldisc o_ldisc, new_ldisc;
         int work;
         unsigned long flags;
-        struct tty_ldisc *ld;
         struct tty_struct *o_tty;
 
-        if ((ldisc < N_TTY) || (ldisc >= NR_LDISCS))
-                return -EINVAL;
-
 restart:
-
-        ld = tty_ldisc_get(ldisc);
-        /* Eduardo Blanco <ejbs@cs.cs.com.uy> */
-        /* Cyrus Durgin <cider@speakeasy.org> */
-        if (ld == NULL) {
-                request_module("tty-ldisc-%d", ldisc);
-                ld = tty_ldisc_get(ldisc);
-        }
-        if (ld == NULL)
-                return -EINVAL;
+        /* This is a bit ugly for now but means we can break the 'ldisc
+           is part of the tty struct' assumption later */
+        retval = tty_ldisc_get(ldisc, &new_ldisc);
+        if (retval)
+                return retval;
 
         /*
          *      Problem: What do we do if this blocks ?
@@ -996,8 +1091,8 @@ restart:
 
         tty_wait_until_sent(tty, 0);
 
-        if (tty->ldisc.num == ldisc) {
-                tty_ldisc_put(ldisc);
+        if (tty->ldisc.ops->num == ldisc) {
+                tty_ldisc_put(new_ldisc.ops);
                 return 0;
         }
 
@@ -1024,7 +1119,7 @@ restart:
                         /* Free the new ldisc we grabbed. Must drop the lock
                            first. */
                         spin_unlock_irqrestore(&tty_ldisc_lock, flags);
-                        tty_ldisc_put(ldisc);
+                        tty_ldisc_put(o_ldisc.ops);
                         /*
                          * There are several reasons we may be busy, including
                          * random momentary I/O traffic. We must therefore
@@ -1038,7 +1133,7 @@ restart:
                 }
                 if (o_tty && o_tty->ldisc.refcount) {
                         spin_unlock_irqrestore(&tty_ldisc_lock, flags);
-                        tty_ldisc_put(ldisc);
+                        tty_ldisc_put(o_tty->ldisc.ops);
                         if (wait_event_interruptible(tty_ldisc_wait, o_tty->ldisc.refcount == 0) < 0)
                                 return -ERESTARTSYS;
                         goto restart;
@@ -1049,8 +1144,9 @@ restart:
          *      another ldisc change
          */
         if (!test_bit(TTY_LDISC, &tty->flags)) {
+                struct tty_ldisc *ld;
                 spin_unlock_irqrestore(&tty_ldisc_lock, flags);
-                tty_ldisc_put(ldisc);
+                tty_ldisc_put(new_ldisc.ops);
                 ld = tty_ldisc_ref_wait(tty);
                 tty_ldisc_deref(ld);
                 goto restart;
@@ -1060,7 +1156,7 @@ restart:
         if (o_tty)
                 clear_bit(TTY_LDISC, &o_tty->flags);
         spin_unlock_irqrestore(&tty_ldisc_lock, flags);
-
+        
         /*
          *      From this point on we know nobody has an ldisc
          *      usage reference, nor can they obtain one until
@@ -1070,45 +1166,30 @@ restart:
         work = cancel_delayed_work(&tty->buf.work);
         /*
          * Wait for ->hangup_work and ->buf.work handlers to terminate
+         * MUST NOT hold locks here.
          */
         flush_scheduled_work();
         /* Shutdown the current discipline. */
-        if (tty->ldisc.close)
-                (tty->ldisc.close)(tty);
+        if (o_ldisc.ops->close)
+                (o_ldisc.ops->close)(tty);
 
         /* Now set up the new line discipline. */
-        tty_ldisc_assign(tty, ld);
+        tty_ldisc_assign(tty, &new_ldisc);
         tty_set_termios_ldisc(tty, ldisc);
-        if (tty->ldisc.open)
-                retval = (tty->ldisc.open)(tty);
+        if (new_ldisc.ops->open)
+                retval = (new_ldisc.ops->open)(tty);
         if (retval < 0) {
-                tty_ldisc_put(ldisc);
-                /* There is an outstanding reference here so this is safe */
-                tty_ldisc_assign(tty, tty_ldisc_get(o_ldisc.num));
-                tty_set_termios_ldisc(tty, tty->ldisc.num);
-                if (tty->ldisc.open && (tty->ldisc.open(tty) < 0)) {
-                        tty_ldisc_put(o_ldisc.num);
-                        /* This driver is always present */
-                        tty_ldisc_assign(tty, tty_ldisc_get(N_TTY));
-                        tty_set_termios_ldisc(tty, N_TTY);
-                        if (tty->ldisc.open) {
-                                int r = tty->ldisc.open(tty);
-
-                                if (r < 0)
-                                        panic("Couldn't open N_TTY ldisc for "
-                                              "%s --- error %d.",
-                                              tty_name(tty, buf), r);
-                        }
-                }
+                tty_ldisc_put(new_ldisc.ops);
+                tty_ldisc_restore(tty, &o_ldisc);
         }
         /* At this point we hold a reference to the new ldisc and a
            a reference to the old ldisc. If we ended up flipping back
            to the existing ldisc we have two references to it */
 
-        if (tty->ldisc.num != o_ldisc.num && tty->ops->set_ldisc)
+        if (tty->ldisc.ops->num != o_ldisc.ops->num && tty->ops->set_ldisc)
                 tty->ops->set_ldisc(tty);
 
-        tty_ldisc_put(o_ldisc.num);
+        tty_ldisc_put(o_ldisc.ops);
 
         /*
          *      Allow ldisc referencing to occur as soon as the driver
@@ -1335,8 +1416,8 @@ void tty_wakeup(struct tty_struct *tty)
         if (test_bit(TTY_DO_WRITE_WAKEUP, &tty->flags)) {
                 ld = tty_ldisc_ref(tty);
                 if (ld) {
-                        if (ld->write_wakeup)
-                                ld->write_wakeup(tty);
+                        if (ld->ops->write_wakeup)
+                                ld->ops->write_wakeup(tty);
                         tty_ldisc_deref(ld);
                 }
         }
@@ -1357,8 +1438,8 @@ void tty_ldisc_flush(struct tty_struct *tty)
 {
         struct tty_ldisc *ld = tty_ldisc_ref(tty);
         if (ld) {
-                if (ld->flush_buffer)
-                        ld->flush_buffer(tty);
+                if (ld->ops->flush_buffer)
+                        ld->ops->flush_buffer(tty);
                 tty_ldisc_deref(ld);
         }
         tty_buffer_flush(tty);
@@ -1386,7 +1467,7 @@ static void tty_reset_termios(struct tty_struct *tty)
  *      do_tty_hangup           -       actual handler for hangup events
  *      @work: tty device
  *
- *      This can be called by the "eventd" kernel thread.  That is process
+k *     This can be called by the "eventd" kernel thread.  That is process
  *      synchronous but doesn't hold any locks, so we need to make sure we
  *      have the appropriate locks for what we're doing.
  *
@@ -1449,14 +1530,14 @@ static void do_tty_hangup(struct work_struct *work)
         ld = tty_ldisc_ref(tty);
         if (ld != NULL) {
                 /* We may have no line discipline at this point */
-                if (ld->flush_buffer)
-                        ld->flush_buffer(tty);
+                if (ld->ops->flush_buffer)
+                        ld->ops->flush_buffer(tty);
                 tty_driver_flush_buffer(tty);
                 if ((test_bit(TTY_DO_WRITE_WAKEUP, &tty->flags)) &&
-                    ld->write_wakeup)
-                        ld->write_wakeup(tty);
-                if (ld->hangup)
-                        ld->hangup(tty);
+                    ld->ops->write_wakeup)
+                        ld->ops->write_wakeup(tty);
+                if (ld->ops->hangup)
+                        ld->ops->hangup(tty);
         }
         /*
          * FIXME: Once we trust the LDISC code better we can wait here for
@@ -1825,8 +1906,8 @@ static ssize_t tty_read(struct file *file, char __user *buf, size_t count,
         /* We want to wait for the line discipline to sort out in this
            situation */
         ld = tty_ldisc_ref_wait(tty);
-        if (ld->read)
-                i = (ld->read)(tty, file, buf, count);
+        if (ld->ops->read)
+                i = (ld->ops->read)(tty, file, buf, count);
         else
                 i = -EIO;
         tty_ldisc_deref(ld);
@@ -1978,10 +2059,10 @@ static ssize_t tty_write(struct file *file, const char __user *buf,
                 printk(KERN_ERR "tty driver %s lacks a write_room method.\n",
                         tty->driver->name);
         ld = tty_ldisc_ref_wait(tty);
-        if (!ld->write)
+        if (!ld->ops->write)
                 ret = -EIO;
         else
-                ret = do_tty_write(ld->write, tty, file, buf, count);
+                ret = do_tty_write(ld->ops->write, tty, file, buf, count);
         tty_ldisc_deref(ld);
         return ret;
 }
@@ -2076,6 +2157,7 @@ static int init_dev(struct tty_driver *driver, int idx,
         struct ktermios *tp, **tp_loc, *o_tp, **o_tp_loc;
         struct ktermios *ltp, **ltp_loc, *o_ltp, **o_ltp_loc;
         int retval = 0;
+        struct tty_ldisc *ld;
 
         /* check whether we're reopening an existing tty */
         if (driver->flags & TTY_DRIVER_DEVPTS_MEM) {
@@ -2224,17 +2306,19 @@ static int init_dev(struct tty_driver *driver, int idx,
          * If we fail here just call release_tty to clean up.  No need
          * to decrement the use counts, as release_tty doesn't care.
          */
+         
+        ld = &tty->ldisc;
 
-        if (tty->ldisc.open) {
-                retval = (tty->ldisc.open)(tty);
+        if (ld->ops->open) {
+                retval = (ld->ops->open)(tty);
                 if (retval)
                         goto release_mem_out;
         }
-        if (o_tty && o_tty->ldisc.open) {
-                retval = (o_tty->ldisc.open)(o_tty);
+        if (o_tty && o_tty->ldisc.ops->open) {
+                retval = (o_tty->ldisc.ops->open)(o_tty);
                 if (retval) {
-                        if (tty->ldisc.close)
-                                (tty->ldisc.close)(tty);
+                        if (ld->ops->close)
+                                (ld->ops->close)(tty);
                         goto release_mem_out;
                 }
                 tty_ldisc_enable(o_tty);
@@ -2378,6 +2462,7 @@ static void release_tty(struct tty_struct *tty, int idx)
 static void release_dev(struct file *filp)
 {
         struct tty_struct *tty, *o_tty;
+        struct tty_ldisc ld;
         int     pty_master, tty_closing, o_tty_closing, do_sleep;
         int     devpts;
         int     idx;
@@ -2611,26 +2696,27 @@ static void release_dev(struct file *filp)
         spin_unlock_irqrestore(&tty_ldisc_lock, flags);
         /*
          * Shutdown the current line discipline, and reset it to N_TTY.
-         * N.B. why reset ldisc when we're releasing the memory??
          *
          * FIXME: this MUST get fixed for the new reflocking
          */
-        if (tty->ldisc.close)
-                (tty->ldisc.close)(tty);
-        tty_ldisc_put(tty->ldisc.num);
+        if (tty->ldisc.ops->close)
+                (tty->ldisc.ops->close)(tty);
+        tty_ldisc_put(tty->ldisc.ops);
 
         /*
          *      Switch the line discipline back
          */
-        tty_ldisc_assign(tty, tty_ldisc_get(N_TTY));
+        WARN_ON(tty_ldisc_get(N_TTY, &ld));
+        tty_ldisc_assign(tty, &ld);
         tty_set_termios_ldisc(tty, N_TTY);
         if (o_tty) {
                 /* FIXME: could o_tty be in setldisc here ? */
                 clear_bit(TTY_LDISC, &o_tty->flags);
-                if (o_tty->ldisc.close)
-                        (o_tty->ldisc.close)(o_tty);
-                tty_ldisc_put(o_tty->ldisc.num);
-                tty_ldisc_assign(o_tty, tty_ldisc_get(N_TTY));
+                if (o_tty->ldisc.ops->close)
+                        (o_tty->ldisc.ops->close)(o_tty);
+                tty_ldisc_put(o_tty->ldisc.ops);
+                WARN_ON(tty_ldisc_get(N_TTY, &ld));
+                tty_ldisc_assign(o_tty, &ld);
                 tty_set_termios_ldisc(o_tty, N_TTY);
         }
         /*
@@ -2899,8 +2985,8 @@ static unsigned int tty_poll(struct file *filp, poll_table *wait)
                 return 0;
 
         ld = tty_ldisc_ref_wait(tty);
-        if (ld->poll)
-                ret = (ld->poll)(tty, filp, wait);
+        if (ld->ops->poll)
+                ret = (ld->ops->poll)(tty, filp, wait);
         tty_ldisc_deref(ld);
         return ret;
 }
@@ -2974,7 +3060,7 @@ static int tiocsti(struct tty_struct *tty, char __user *p)
         if (get_user(ch, p))
                 return -EFAULT;
         ld = tty_ldisc_ref_wait(tty);
-        ld->receive_buf(tty, &ch, &mbz, 1);
+        ld->ops->receive_buf(tty, &ch, &mbz, 1);
         tty_ldisc_deref(ld);
         return 0;
 }
@@ -3528,7 +3614,7 @@ long tty_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
         case TIOCGSID:
                 return tiocgsid(tty, real_tty, p);
         case TIOCGETD:
-                return put_user(tty->ldisc.num, (int __user *)p);
+                return put_user(tty->ldisc.ops->num, (int __user *)p);
         case TIOCSETD:
                 return tiocsetd(tty, p);
 #ifdef CONFIG_VT
@@ -3581,8 +3667,8 @@ long tty_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
         }
         ld = tty_ldisc_ref_wait(tty);
         retval = -EINVAL;
-        if (ld->ioctl) {
-                retval = ld->ioctl(tty, file, cmd, arg);
+        if (ld->ops->ioctl) {
+                retval = ld->ops->ioctl(tty, file, cmd, arg);
                 if (retval == -ENOIOCTLCMD)
                         retval = -EINVAL;
         }
@@ -3609,8 +3695,8 @@ static long tty_compat_ioctl(struct file *file, unsigned int cmd,
         }
 
         ld = tty_ldisc_ref_wait(tty);
-        if (ld->compat_ioctl)
-                retval = ld->compat_ioctl(tty, file, cmd, arg);
+        if (ld->ops->compat_ioctl)
+                retval = ld->ops->compat_ioctl(tty, file, cmd, arg);
         tty_ldisc_deref(ld);
 
         return retval;
@@ -3782,7 +3868,8 @@ static void flush_to_ldisc(struct work_struct *work)
                         flag_buf = head->flag_buf_ptr + head->read;
                         head->read += count;
                         spin_unlock_irqrestore(&tty->buf.lock, flags);
-                        disc->receive_buf(tty, char_buf, flag_buf, count);
+                        disc->ops->receive_buf(tty, char_buf,
+                                                        flag_buf, count);
                         spin_lock_irqsave(&tty->buf.lock, flags);
                 }
                 /* Restore the queue head */
@@ -3843,9 +3930,12 @@ EXPORT_SYMBOL(tty_flip_buffer_push);
 
 static void initialize_tty_struct(struct tty_struct *tty)
 {
+        struct tty_ldisc ld;
         memset(tty, 0, sizeof(struct tty_struct));
         tty->magic = TTY_MAGIC;
-        tty_ldisc_assign(tty, tty_ldisc_get(N_TTY));
+        if (tty_ldisc_get(N_TTY, &ld) < 0)
+                panic("n_tty: init_tty");
+        tty_ldisc_assign(tty, &ld);
         tty->session = NULL;
         tty->pgrp = NULL;
         tty->overrun_time = jiffies;
diff --git a/drivers/char/tty_ioctl.c b/drivers/char/tty_ioctl.c
index 8f81139d6194..ea9fc5d03b99 100644
--- a/drivers/char/tty_ioctl.c
+++ b/drivers/char/tty_ioctl.c
@@ -491,8 +491,8 @@ static void change_termios(struct tty_struct *tty, struct ktermios *new_termios)
 
         ld = tty_ldisc_ref(tty);
         if (ld != NULL) {
-                if (ld->set_termios)
-                        (ld->set_termios)(tty, &old_termios);
+                if (ld->ops->set_termios)
+                        (ld->ops->set_termios)(tty, &old_termios);
                 tty_ldisc_deref(ld);
         }
         mutex_unlock(&tty->termios_mutex);
@@ -552,8 +552,8 @@ static int set_termios(struct tty_struct *tty, void __user *arg, int opt)
         ld = tty_ldisc_ref(tty);
 
         if (ld != NULL) {
-                if ((opt & TERMIOS_FLUSH) && ld->flush_buffer)
-                        ld->flush_buffer(tty);
+                if ((opt & TERMIOS_FLUSH) && ld->ops->flush_buffer)
+                        ld->ops->flush_buffer(tty);
                 tty_ldisc_deref(ld);
         }
 
@@ -959,12 +959,12 @@ int tty_perform_flush(struct tty_struct *tty, unsigned long arg)
         ld = tty_ldisc_ref(tty);
         switch (arg) {
         case TCIFLUSH:
-                if (ld && ld->flush_buffer)
-                        ld->flush_buffer(tty);
+                if (ld && ld->ops->flush_buffer)
+                        ld->ops->flush_buffer(tty);
                 break;
         case TCIOFLUSH:
-                if (ld && ld->flush_buffer)
-                        ld->flush_buffer(tty);
+                if (ld && ld->ops->flush_buffer)
+                        ld->ops->flush_buffer(tty);
                 /* fall through */
         case TCOFLUSH:
                 tty_driver_flush_buffer(tty);