tty: The big operations rework

- Operations are now a shared const function block as with most other Linux
  objects

- Introduce wrappers for some optional functions to get consistent behaviour

- Wrap put_char which used to be patched by the tty layer

- Document which functions are needed/optional

- Make put_char report success/fail

- Cache the driver->ops pointer in the tty as tty->ops

- Remove various surplus lock calls we no longer need

- Remove proc_write method as noted by Alexey Dobriyan

- Introduce some missing sanity checks where certain driver/ldisc
  combinations would oops as they didn't check needed methods were present

[akpm@linux-foundation.org: fix fs/compat_ioctl.c build]
[akpm@linux-foundation.org: fix isicom]
[akpm@linux-foundation.org: fix arch/ia64/hp/sim/simserial.c build]
[akpm@linux-foundation.org: fix kgdb]
Signed-off-by: Alan Cox <alan@redhat.com>
Acked-by: Greg Kroah-Hartman <gregkh@suse.de>
Cc: Jason Wessel <jason.wessel@windriver.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

2 files changed, 27 insertions, 24 deletions

diff --git a/drivers/net/hamradio/6pack.c b/drivers/net/hamradio/6pack.c
index 1da55dd2a5a0..82a36266dfc9 100644
--- a/drivers/net/hamradio/6pack.c
+++ b/drivers/net/hamradio/6pack.c
@@ -148,13 +148,13 @@ static void sp_xmit_on_air(unsigned long channel)
 
         if (((sp->status1 & SIXP_DCD_MASK) == 0) && (random < sp->persistence)) {
                 sp->led_state = 0x70;
-                sp->tty->driver->write(sp->tty, &sp->led_state, 1);
+                sp->tty->ops->write(sp->tty, &sp->led_state, 1);
                 sp->tx_enable = 1;
-                actual = sp->tty->driver->write(sp->tty, sp->xbuff, sp->status2);
+                actual = sp->tty->ops->write(sp->tty, sp->xbuff, sp->status2);
                 sp->xleft -= actual;
                 sp->xhead += actual;
                 sp->led_state = 0x60;
-                sp->tty->driver->write(sp->tty, &sp->led_state, 1);
+                sp->tty->ops->write(sp->tty, &sp->led_state, 1);
                 sp->status2 = 0;
         } else
                 mod_timer(&sp->tx_t, jiffies + ((when + 1) * HZ) / 100);
@@ -220,13 +220,13 @@ static void sp_encaps(struct sixpack *sp, unsigned char *icp, int len)
          */
         if (sp->duplex == 1) {
                 sp->led_state = 0x70;
-                sp->tty->driver->write(sp->tty, &sp->led_state, 1);
+                sp->tty->ops->write(sp->tty, &sp->led_state, 1);
                 sp->tx_enable = 1;
-                actual = sp->tty->driver->write(sp->tty, sp->xbuff, count);
+                actual = sp->tty->ops->write(sp->tty, sp->xbuff, count);
                 sp->xleft = count - actual;
                 sp->xhead = sp->xbuff + actual;
                 sp->led_state = 0x60;
-                sp->tty->driver->write(sp->tty, &sp->led_state, 1);
+                sp->tty->ops->write(sp->tty, &sp->led_state, 1);
         } else {
                 sp->xleft = count;
                 sp->xhead = sp->xbuff;
@@ -444,7 +444,7 @@ static void sixpack_write_wakeup(struct tty_struct *tty)
         }
 
         if (sp->tx_enable) {
-                actual = tty->driver->write(tty, sp->xhead, sp->xleft);
+                actual = tty->ops->write(tty, sp->xhead, sp->xleft);
                 sp->xleft -= actual;
                 sp->xhead += actual;
         }
@@ -492,8 +492,8 @@ static void sixpack_receive_buf(struct tty_struct *tty,
 
         sp_put(sp);
         if (test_and_clear_bit(TTY_THROTTLED, &tty->flags)
-            && tty->driver->unthrottle)
-                tty->driver->unthrottle(tty);
+            && tty->ops->unthrottle)
+                tty->ops->unthrottle(tty);
 }
 
 /*
@@ -554,8 +554,8 @@ static void resync_tnc(unsigned long channel)
         /* resync the TNC */
 
         sp->led_state = 0x60;
-        sp->tty->driver->write(sp->tty, &sp->led_state, 1);
-        sp->tty->driver->write(sp->tty, &resync_cmd, 1);
+        sp->tty->ops->write(sp->tty, &sp->led_state, 1);
+        sp->tty->ops->write(sp->tty, &resync_cmd, 1);
 
 
         /* Start resync timer again -- the TNC might be still absent */
@@ -573,7 +573,7 @@ static inline int tnc_init(struct sixpack *sp)
 
         tnc_set_sync_state(sp, TNC_UNSYNC_STARTUP);
 
-        sp->tty->driver->write(sp->tty, &inbyte, 1);
+        sp->tty->ops->write(sp->tty, &inbyte, 1);
 
         del_timer(&sp->resync_t);
         sp->resync_t.data = (unsigned long) sp;
@@ -601,6 +601,8 @@ static int sixpack_open(struct tty_struct *tty)
 
         if (!capable(CAP_NET_ADMIN))
                 return -EPERM;
+        if (tty->ops->write == NULL)
+                return -EOPNOTSUPP;
 
         dev = alloc_netdev(sizeof(struct sixpack), "sp%d", sp_setup);
         if (!dev) {
@@ -914,9 +916,9 @@ static void decode_prio_command(struct sixpack *sp, unsigned char cmd)
         } else { /* output watchdog char if idle */
                 if ((sp->status2 != 0) && (sp->duplex == 1)) {
                         sp->led_state = 0x70;
-                        sp->tty->driver->write(sp->tty, &sp->led_state, 1);
+                        sp->tty->ops->write(sp->tty, &sp->led_state, 1);
                         sp->tx_enable = 1;
-                        actual = sp->tty->driver->write(sp->tty, sp->xbuff, sp->status2);
+                        actual = sp->tty->ops->write(sp->tty, sp->xbuff, sp->status2);
                         sp->xleft -= actual;
                         sp->xhead += actual;
                         sp->led_state = 0x60;
@@ -926,7 +928,7 @@ static void decode_prio_command(struct sixpack *sp, unsigned char cmd)
         }
 
         /* needed to trigger the TNC watchdog */
-        sp->tty->driver->write(sp->tty, &sp->led_state, 1);
+        sp->tty->ops->write(sp->tty, &sp->led_state, 1);
 
         /* if the state byte has been received, the TNC is present,
            so the resync timer can be reset. */
@@ -956,12 +958,12 @@ static void decode_std_command(struct sixpack *sp, unsigned char cmd)
                         if ((sp->status & SIXP_RX_DCD_MASK) ==
                                 SIXP_RX_DCD_MASK) {
                                 sp->led_state = 0x68;
-                                sp->tty->driver->write(sp->tty, &sp->led_state, 1);
+                                sp->tty->ops->write(sp->tty, &sp->led_state, 1);
                         }
                 } else {
                         sp->led_state = 0x60;
                         /* fill trailing bytes with zeroes */
-                        sp->tty->driver->write(sp->tty, &sp->led_state, 1);
+                        sp->tty->ops->write(sp->tty, &sp->led_state, 1);
                         rest = sp->rx_count;
                         if (rest != 0)
                                  for (i = rest; i <= 3; i++)
diff --git a/drivers/net/hamradio/mkiss.c b/drivers/net/hamradio/mkiss.c
index 30c9b3b0d131..ebcc5adee7cc 100644
--- a/drivers/net/hamradio/mkiss.c
+++ b/drivers/net/hamradio/mkiss.c
@@ -516,7 +516,7 @@ static void ax_encaps(struct net_device *dev, unsigned char *icp, int len)
         spin_unlock_bh(&ax->buflock);
 
         set_bit(TTY_DO_WRITE_WAKEUP, &ax->tty->flags);
-        actual = ax->tty->driver->write(ax->tty, ax->xbuff, count);
+        actual = ax->tty->ops->write(ax->tty, ax->xbuff, count);
         ax->stats.tx_packets++;
         ax->stats.tx_bytes += actual;
 
@@ -546,7 +546,7 @@ static int ax_xmit(struct sk_buff *skb, struct net_device *dev)
                 }
 
                 printk(KERN_ERR "mkiss: %s: transmit timed out, %s?\n", dev->name,
-                       (ax->tty->driver->chars_in_buffer(ax->tty) || ax->xleft) ?
+                       (ax->tty->ops->chars_in_buffer(ax->tty) || ax->xleft) ?
                        "bad line quality" : "driver error");
 
                 ax->xleft = 0;
@@ -736,6 +736,8 @@ static int mkiss_open(struct tty_struct *tty)
 
         if (!capable(CAP_NET_ADMIN))
                 return -EPERM;
+        if (tty->ops->write == NULL)
+                return -EOPNOTSUPP;
 
         dev = alloc_netdev(sizeof(struct mkiss), "ax%d", ax_setup);
         if (!dev) {
@@ -754,8 +756,7 @@ static int mkiss_open(struct tty_struct *tty)
         tty->disc_data = ax;
         tty->receive_room = 65535;
 
-        if (tty->driver->flush_buffer)
-                tty->driver->flush_buffer(tty);
+        tty_driver_flush_buffer(tty);
 
         /* Restore default settings */
         dev->type = ARPHRD_AX25;
@@ -936,8 +937,8 @@ static void mkiss_receive_buf(struct tty_struct *tty, const unsigned char *cp,
 
         mkiss_put(ax);
         if (test_and_clear_bit(TTY_THROTTLED, &tty->flags)
-            && tty->driver->unthrottle)
-                tty->driver->unthrottle(tty);
+            && tty->ops->unthrottle)
+                tty->ops->unthrottle(tty);
 }
 
 /*
@@ -962,7 +963,7 @@ static void mkiss_write_wakeup(struct tty_struct *tty)
                 goto out;
         }
 
-        actual = tty->driver->write(tty, ax->xhead, ax->xleft);
+        actual = tty->ops->write(tty, ax->xhead, ax->xleft);
         ax->xleft -= actual;
         ax->xhead += actual;