tty: More driver operations

We have the lookup operation abstracted which is nice for pty cleanup but
we really want to abstract the add/remove entries as well so that we can
pull the pty code out of the tty core and create a clear defined interface
for the tty driver table.

Signed-off-by: Alan Cox <alan@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

3 files changed, 79 insertions, 10 deletions

diff --git a/drivers/char/pty.c b/drivers/char/pty.c
index 0fdfa0517140..4e6490bda751 100644
--- a/drivers/char/pty.c
+++ b/drivers/char/pty.c
@@ -433,8 +433,22 @@ static void pty_shutdown(struct tty_struct *tty)
         kfree(tty->termios_locked);
 }
 
+/* We have no need to install and remove our tty objects as devpts does all
+   the work for us */
+
+static int pty_install(struct tty_driver *driver, struct tty_struct *tty)
+{
+        return 0;
+}
+
+static void pty_remove(struct tty_driver *driver, struct tty_struct *tty)
+{
+}
+
 static const struct tty_operations ptm_unix98_ops = {
         .lookup = ptm_unix98_lookup,
+        .install = pty_install,
+        .remove = pty_remove,
         .open = pty_open,
         .close = pty_close,
         .write = pty_write,
@@ -449,6 +463,8 @@ static const struct tty_operations ptm_unix98_ops = {
 
 static const struct tty_operations pty_unix98_ops = {
         .lookup = pts_unix98_lookup,
+        .install = pty_install,
+        .remove = pty_remove,
         .open = pty_open,
         .close = pty_close,
         .write = pty_write,
diff --git a/drivers/char/tty_io.c b/drivers/char/tty_io.c
index 47aa437effe2..888380f573dc 100644
--- a/drivers/char/tty_io.c
+++ b/drivers/char/tty_io.c
@@ -1189,7 +1189,7 @@ static void pty_line_name(struct tty_driver *driver, int index, char *p)
 }
 
 /**
- *      pty_line_name   -       generate name for a tty
+ *      tty_line_name   -       generate name for a tty
  *      @driver: the tty driver in use
  *      @index: the minor number
  *      @p: output buffer of at least 7 bytes
@@ -1222,13 +1222,51 @@ struct tty_struct *tty_driver_lookup_tty(struct tty_driver *driver, int idx)
         if (driver->ops->lookup)
                 return driver->ops->lookup(driver, idx);
 
-                tty = driver->ttys[idx];
+        tty = driver->ttys[idx];
         return tty;
 }
 
 /**
- *      tty_reopen()    - fast re-open of an open tty
- *      @tty    - the tty to open
+ *      tty_driver_install_tty() - install a tty entry in the driver
+ *      @driver: the driver for the tty
+ *      @tty: the tty
+ *
+ *      Install a tty object into the driver tables. The tty->index field
+ *      will be set by the time this is called.
+ *
+ *      Locking: tty_mutex for now
+ */
+static int tty_driver_install_tty(struct tty_driver *driver,
+                                                struct tty_struct *tty)
+{
+        if (driver->ops->install)
+                return driver->ops->install(driver, tty);
+        driver->ttys[tty->index] = tty;
+        return 0;
+}
+
+/**
+ *      tty_driver_remove_tty() - remove a tty from the driver tables
+ *      @driver: the driver for the tty
+ *      @idx:    the minor number
+ *
+ *      Remvoe a tty object from the driver tables. The tty->index field
+ *      will be set by the time this is called.
+ *
+ *      Locking: tty_mutex for now
+ */
+static void tty_driver_remove_tty(struct tty_driver *driver,
+                                                struct tty_struct *tty)
+{
+        if (driver->ops->remove)
+                driver->ops->remove(driver, tty);
+        else
+                driver->ttys[tty->index] = NULL;
+}
+
+/*
+ *      tty_reopen()    - fast re-open of an open tty
+ *      @tty    - the tty to open
  *
  *      Return 0 on success, -errno on error.
  *
@@ -1423,11 +1461,7 @@ int tty_init_dev(struct tty_driver *driver, int idx,
          * All structures have been allocated, so now we install them.
          * Failures after this point use release_tty to clean up, so
          * there's no need to null out the local pointers.
-         *
-         * FIXME: We want a 'driver->install method ?
          */
-        if (!(driver->flags & TTY_DRIVER_DEVPTS_MEM))
-                driver->ttys[idx] = tty;
 
         if (!*tp_loc)
                 *tp_loc = tp;
@@ -1441,6 +1475,9 @@ int tty_init_dev(struct tty_driver *driver, int idx,
         tty_driver_kref_get(driver);
         tty->count++;
 
+        if (tty_driver_install_tty(driver, tty) < 0)
+                goto release_mem_out;
+
         /*
          * Structures all installed ... call the ldisc open routines.
          * If we fail here just call release_tty to clean up.  No need
@@ -1502,7 +1539,7 @@ EXPORT_SYMBOL(tty_free_termios);
 
 void tty_shutdown(struct tty_struct *tty)
 {
-        tty->driver->ttys[tty->index] = NULL;
+        tty_driver_remove_tty(tty->driver, tty);
         tty_free_termios(tty);
 }
 EXPORT_SYMBOL(tty_shutdown);
@@ -1615,7 +1652,7 @@ void tty_release_dev(struct file *filp)
                                   "free (%s)\n", tty->name);
                 return;
         }
-        if (!(tty->driver->flags & TTY_DRIVER_DEVPTS_MEM)) {
+        if (!devpts) {
                 if (tty != tty->driver->ttys[idx]) {
                         printk(KERN_DEBUG "tty_release_dev: driver.table[%d] not tty "
                                "for (%s)\n", idx, tty->name);
diff --git a/include/linux/tty_driver.h b/include/linux/tty_driver.h
index ba891dd23550..005d06ad46a6 100644
--- a/include/linux/tty_driver.h
+++ b/include/linux/tty_driver.h
@@ -15,6 +15,20 @@
  *
  *      Optional method. Default behaviour is to use the ttys array
  *
+ * int (*install)(struct tty_driver *self, struct tty_struct *tty)
+ *
+ *      Install a new tty into the tty driver internal tables. Used in
+ *      conjunction with lookup and remove methods.
+ *
+ *      Optional method. Default behaviour is to use the ttys array
+ *
+ * void (*remove)(struct tty_driver *self, struct tty_struct *tty)
+ *
+ *      Remove a closed tty from the tty driver internal tables. Used in
+ *      conjunction with lookup and remove methods.
+ *
+ *      Optional method. Default behaviour is to use the ttys array
+ *
  * int  (*open)(struct tty_struct * tty, struct file * filp);
  *
  *      This routine is called when a particular tty device is opened.
@@ -212,6 +226,8 @@ struct tty_driver;
 
 struct tty_operations {
         struct tty_struct * (*lookup)(struct tty_driver *driver, int idx);
+        int  (*install)(struct tty_driver *driver, struct tty_struct *tty);
+        void (*remove)(struct tty_driver *driver, struct tty_struct *tty);
         int  (*open)(struct tty_struct * tty, struct file * filp);
         void (*close)(struct tty_struct * tty, struct file * filp);
         void (*shutdown)(struct tty_struct *tty);