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>

1 files changed, 42 insertions, 20 deletions

diff --git a/drivers/char/tty_ioctl.c b/drivers/char/tty_ioctl.c
index 8c4bf3e48d5b..c10d40c4c5ca 100644
--- a/drivers/char/tty_ioctl.c
+++ b/drivers/char/tty_ioctl.c
@@ -40,6 +40,34 @@
 #define TERMIOS_OLD     8
 
 
+int tty_chars_in_buffer(struct tty_struct *tty)
+{
+        if (tty->ops->chars_in_buffer)
+                return tty->ops->chars_in_buffer(tty);
+        else
+                return 0;
+}
+
+EXPORT_SYMBOL(tty_chars_in_buffer);
+
+int tty_write_room(struct tty_struct *tty)
+{
+        if (tty->ops->write_room)
+                return tty->ops->write_room(tty);
+        return 2048;
+}
+
+EXPORT_SYMBOL(tty_write_room);
+
+void tty_driver_flush_buffer(struct tty_struct *tty)
+{
+        if (tty->ops->flush_buffer)
+                tty->ops->flush_buffer(tty);
+}
+
+EXPORT_SYMBOL(tty_driver_flush_buffer);
+
+
 /**
  *      tty_wait_until_sent     -       wait for I/O to finish
  *      @tty: tty we are waiting for
@@ -58,17 +86,13 @@ void tty_wait_until_sent(struct tty_struct *tty, long timeout)
 
         printk(KERN_DEBUG "%s wait until sent...\n", tty_name(tty, buf));
 #endif
-        if (!tty->driver->chars_in_buffer)
-                return;
         if (!timeout)
                 timeout = MAX_SCHEDULE_TIMEOUT;
-        lock_kernel();
         if (wait_event_interruptible_timeout(tty->write_wait,
-                        !tty->driver->chars_in_buffer(tty), timeout) >= 0) {
-                if (tty->driver->wait_until_sent)
-                        tty->driver->wait_until_sent(tty, timeout);
+                        !tty_chars_in_buffer(tty), timeout) >= 0) {
+                if (tty->ops->wait_until_sent)
+                        tty->ops->wait_until_sent(tty, timeout);
         }
-        unlock_kernel();
 }
 EXPORT_SYMBOL(tty_wait_until_sent);
 
@@ -444,8 +468,8 @@ static void change_termios(struct tty_struct *tty, struct ktermios *new_termios)
                 }
         }
 
-        if (tty->driver->set_termios)
-                (*tty->driver->set_termios)(tty, &old_termios);
+        if (tty->ops->set_termios)
+                (*tty->ops->set_termios)(tty, &old_termios);
         else
                 tty_termios_copy_hw(tty->termios, &old_termios);
 
@@ -748,8 +772,8 @@ static int send_prio_char(struct tty_struct *tty, char ch)
 {
         int     was_stopped = tty->stopped;
 
-        if (tty->driver->send_xchar) {
-                tty->driver->send_xchar(tty, ch);
+        if (tty->ops->send_xchar) {
+                tty->ops->send_xchar(tty, ch);
                 return 0;
         }
 
@@ -758,7 +782,7 @@ static int send_prio_char(struct tty_struct *tty, char ch)
 
         if (was_stopped)
                 start_tty(tty);
-        tty->driver->write(tty, &ch, 1);
+        tty->ops->write(tty, &ch, 1);
         if (was_stopped)
                 stop_tty(tty);
         tty_write_unlock(tty);
@@ -778,13 +802,14 @@ static int tty_change_softcar(struct tty_struct *tty, int arg)
 {
         int ret = 0;
         int bit = arg ? CLOCAL : 0;
-        struct ktermios old = *tty->termios;
+        struct ktermios old;
 
         mutex_lock(&tty->termios_mutex);
+        old = *tty->termios;
         tty->termios->c_cflag &= ~CLOCAL;
         tty->termios->c_cflag |= bit;
-        if (tty->driver->set_termios)
-                tty->driver->set_termios(tty, &old);
+        if (tty->ops->set_termios)
+                tty->ops->set_termios(tty, &old);
         if ((tty->termios->c_cflag & CLOCAL) != bit)
                 ret = -EINVAL;
         mutex_unlock(&tty->termios_mutex);
@@ -926,8 +951,7 @@ int tty_perform_flush(struct tty_struct *tty, unsigned long arg)
                         ld->flush_buffer(tty);
                 /* fall through */
         case TCOFLUSH:
-                if (tty->driver->flush_buffer)
-                        tty->driver->flush_buffer(tty);
+                tty_driver_flush_buffer(tty);
                 break;
         default:
                 tty_ldisc_deref(ld);
@@ -984,9 +1008,7 @@ int n_tty_ioctl(struct tty_struct *tty, struct file *file,
         case TCFLSH:
                 return tty_perform_flush(tty, arg);
         case TIOCOUTQ:
-                return put_user(tty->driver->chars_in_buffer ?
-                                tty->driver->chars_in_buffer(tty) : 0,
-                                (int __user *) arg);
+                return put_user(tty_chars_in_buffer(tty), (int __user *) arg);
         case TIOCINQ:
                 retval = tty->read_cnt;
                 if (L_ICANON(tty))