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, 23 insertions, 106 deletions

diff --git a/drivers/usb/serial/usb-serial.c b/drivers/usb/serial/usb-serial.c
index a9934a3f9845..0cb0d77dc429 100644
--- a/drivers/usb/serial/usb-serial.c
+++ b/drivers/usb/serial/usb-serial.c
@@ -296,16 +296,14 @@ static int serial_write (struct tty_struct * tty, const unsigned char *buf, int
         struct usb_serial_port *port = tty->driver_data;
         int retval = -ENODEV;
 
-        if (!port || port->serial->dev->state == USB_STATE_NOTATTACHED)
+        if (port->serial->dev->state == USB_STATE_NOTATTACHED)
                 goto exit;
 
         dbg("%s - port %d, %d byte(s)", __func__, port->number, count);
 
-        if (!port->open_count) {
-                retval = -EINVAL;
-                dbg("%s - port not opened", __func__);
-                goto exit;
-        }
+        /* open_count is managed under the mutex lock for the tty so cannot
+           drop to zero until after the last close completes */
+        WARN_ON(!port->open_count);
 
         /* pass on to the driver specific version of this function */
         retval = port->serial->type->write(port, buf, count);
@@ -317,61 +315,28 @@ exit:
 static int serial_write_room (struct tty_struct *tty) 
 {
         struct usb_serial_port *port = tty->driver_data;
-        int retval = -ENODEV;
-
-        if (!port)
-                goto exit;
-
         dbg("%s - port %d", __func__, port->number);
-
-        if (!port->open_count) {
-                dbg("%s - port not open", __func__);
-                goto exit;
-        }
-
+        WARN_ON(!port->open_count);
         /* pass on to the driver specific version of this function */
-        retval = port->serial->type->write_room(port);
-
-exit:
-        return retval;
+        return port->serial->type->write_room(port);
 }
 
 static int serial_chars_in_buffer (struct tty_struct *tty) 
 {
         struct usb_serial_port *port = tty->driver_data;
-        int retval = -ENODEV;
-
-        if (!port)
-                goto exit;
-
         dbg("%s = port %d", __func__, port->number);
 
-        if (!port->open_count) {
-                dbg("%s - port not open", __func__);
-                goto exit;
-        }
-
+        WARN_ON(!port->open_count);
         /* pass on to the driver specific version of this function */
-        retval = port->serial->type->chars_in_buffer(port);
-
-exit:
-        return retval;
+        return port->serial->type->chars_in_buffer(port);
 }
 
 static void serial_throttle (struct tty_struct * tty)
 {
         struct usb_serial_port *port = tty->driver_data;
-
-        if (!port)
-                return;
-
         dbg("%s - port %d", __func__, port->number);
 
-        if (!port->open_count) {
-                dbg ("%s - port not open", __func__);
-                return;
-        }
-
+        WARN_ON(!port->open_count);
         /* pass on to the driver specific version of this function */
         if (port->serial->type->throttle)
                 port->serial->type->throttle(port);
@@ -380,17 +345,9 @@ static void serial_throttle (struct tty_struct * tty)
 static void serial_unthrottle (struct tty_struct * tty)
 {
         struct usb_serial_port *port = tty->driver_data;
-
-        if (!port)
-                return;
-
         dbg("%s - port %d", __func__, port->number);
 
-        if (!port->open_count) {
-                dbg("%s - port not open", __func__);
-                return;
-        }
-
+        WARN_ON(!port->open_count);
         /* pass on to the driver specific version of this function */
         if (port->serial->type->unthrottle)
                 port->serial->type->unthrottle(port);
@@ -401,42 +358,27 @@ static int serial_ioctl (struct tty_struct *tty, struct file * file, unsigned in
         struct usb_serial_port *port = tty->driver_data;
         int retval = -ENODEV;
 
-        lock_kernel();
-        if (!port)
-                goto exit;
-
         dbg("%s - port %d, cmd 0x%.4x", __func__, port->number, cmd);
 
-        /* Caution - port->open_count is BKL protected */
-        if (!port->open_count) {
-                dbg ("%s - port not open", __func__);
-                goto exit;
-        }
+        WARN_ON(!port->open_count);
 
         /* pass on to the driver specific version of this function if it is available */
-        if (port->serial->type->ioctl)
+        if (port->serial->type->ioctl) {
+                lock_kernel();
                 retval = port->serial->type->ioctl(port, file, cmd, arg);
+                unlock_kernel();
+        }
         else
                 retval = -ENOIOCTLCMD;
-exit:
-        unlock_kernel();
         return retval;
 }
 
 static void serial_set_termios (struct tty_struct *tty, struct ktermios * old)
 {
         struct usb_serial_port *port = tty->driver_data;
-
-        if (!port)
-                return;
-
         dbg("%s - port %d", __func__, port->number);
 
-        if (!port->open_count) {
-                dbg("%s - port not open", __func__);
-                return;
-        }
-
+        WARN_ON(!port->open_count);
         /* pass on to the driver specific version of this function if it is available */
         if (port->serial->type->set_termios)
                 port->serial->type->set_termios(port, old);
@@ -448,24 +390,15 @@ static void serial_break (struct tty_struct *tty, int break_state)
 {
         struct usb_serial_port *port = tty->driver_data;
 
-        lock_kernel();
-        if (!port) {
-                unlock_kernel();
-                return;
-        }
-
         dbg("%s - port %d", __func__, port->number);
 
-        if (!port->open_count) {
-                dbg("%s - port not open", __func__);
-                unlock_kernel();
-                return;
-        }
-
+        WARN_ON(!port->open_count);
         /* pass on to the driver specific version of this function if it is available */
-        if (port->serial->type->break_ctl)
+        if (port->serial->type->break_ctl) {
+                lock_kernel();
                 port->serial->type->break_ctl(port, break_state);
-        unlock_kernel();
+                unlock_kernel();
+        }
 }
 
 static int serial_read_proc (char *page, char **start, off_t off, int count, int *eof, void *data)
@@ -519,19 +452,11 @@ static int serial_tiocmget (struct tty_struct *tty, struct file *file)
 {
         struct usb_serial_port *port = tty->driver_data;
 
-        if (!port)
-                return -ENODEV;
-
         dbg("%s - port %d", __func__, port->number);
 
-        if (!port->open_count) {
-                dbg("%s - port not open", __func__);
-                return -ENODEV;
-        }
-
+        WARN_ON(!port->open_count);
         if (port->serial->type->tiocmget)
                 return port->serial->type->tiocmget(port, file);
-
         return -EINVAL;
 }
 
@@ -540,19 +465,11 @@ static int serial_tiocmset (struct tty_struct *tty, struct file *file,
 {
         struct usb_serial_port *port = tty->driver_data;
 
-        if (!port)
-                return -ENODEV;
-
         dbg("%s - port %d", __func__, port->number);
 
-        if (!port->open_count) {
-                dbg("%s - port not open", __func__);
-                return -ENODEV;
-        }
-
+        WARN_ON(!port->open_count);
         if (port->serial->type->tiocmset)
                 return port->serial->type->tiocmset(port, file, set, clear);
-
         return -EINVAL;
 }