tty: tty_port: Add a kref object to the tty port

Users of tty port need a way to refcount ports when hotplugging is
involved.

Signed-off-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

2 files changed, 30 insertions, 0 deletions

diff --git a/drivers/char/tty_port.c b/drivers/char/tty_port.c
index 84006de2900f..be492dd66437 100644
--- a/drivers/char/tty_port.c
+++ b/drivers/char/tty_port.c
@@ -29,6 +29,7 @@ void tty_port_init(struct tty_port *port)
         spin_lock_init(&port->lock);
         port->close_delay = (50 * HZ) / 100;
         port->closing_wait = (3000 * HZ) / 100;
+        kref_init(&port->kref);
 }
 EXPORT_SYMBOL(tty_port_init);
 
@@ -56,6 +57,23 @@ void tty_port_free_xmit_buf(struct tty_port *port)
 }
 EXPORT_SYMBOL(tty_port_free_xmit_buf);
 
+static void tty_port_destructor(struct kref *kref)
+{
+        struct tty_port *port = container_of(kref, struct tty_port, kref);
+        if (port->xmit_buf)
+                free_page((unsigned long)port->xmit_buf);
+        if (port->ops->destruct)
+                port->ops->destruct(port);
+        else
+                kfree(port);
+}
+
+void tty_port_put(struct tty_port *port)
+{
+        if (port)
+                kref_put(&port->kref, tty_port_destructor);
+}
+EXPORT_SYMBOL(tty_port_put);
 
 /**
  *      tty_port_tty_get        -       get a tty reference
diff --git a/include/linux/tty.h b/include/linux/tty.h
index e9269ca1542a..e6da667ba34d 100644
--- a/include/linux/tty.h
+++ b/include/linux/tty.h
@@ -199,6 +199,8 @@ struct tty_port_operations {
         /* FIXME: long term getting the tty argument *out* of this would be
            good for consoles */
         int (*activate)(struct tty_port *port, struct tty_struct *tty);
+        /* Called on the final put of a port */
+        void (*destruct)(struct tty_port *port);
 };
         
 struct tty_port {
@@ -219,6 +221,7 @@ struct tty_port {
         int                     drain_delay;    /* Set to zero if no pure time
                                                    based drain is needed else
                                                    set to size of fifo */
+        struct kref             kref;           /* Ref counter */
 };
 
 /*
@@ -461,6 +464,15 @@ extern int tty_write_lock(struct tty_struct *tty, int ndelay);
 extern void tty_port_init(struct tty_port *port);
 extern int tty_port_alloc_xmit_buf(struct tty_port *port);
 extern void tty_port_free_xmit_buf(struct tty_port *port);
+extern void tty_port_put(struct tty_port *port);
+
+extern inline struct tty_port *tty_port_get(struct tty_port *port)
+{
+        if (port)
+                kref_get(&port->kref);
+        return port;
+}
+
 extern struct tty_struct *tty_port_tty_get(struct tty_port *port);
 extern void tty_port_tty_set(struct tty_port *port, struct tty_struct *tty);
 extern int tty_port_carrier_raised(struct tty_port *port);