tty: usb-serial krefs

Use kref in the USB serial drivers so that we don't free tty structures
from under the URB receive handlers as has historically been the case if
you were unlucky. This also gives us a framework for general tty drivers to
use tty_port objects and refcount.

Contains two err->dev_err changes merged together to fix clashes in the
-next tree.

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

1 files changed, 41 insertions, 0 deletions

diff --git a/drivers/char/tty_port.c b/drivers/char/tty_port.c
index 6fadb19d630..553b0e9d8d1 100644
--- a/drivers/char/tty_port.c
+++ b/drivers/char/tty_port.c
@@ -23,6 +23,7 @@ void tty_port_init(struct tty_port *port)
 	init_waitqueue_head(&port->open_wait);
 	init_waitqueue_head(&port->close_wait);
 	mutex_init(&port->mutex);
+	spin_lock_init(&port->lock);
 	port->close_delay = (50 * HZ) / 100;
 	port->closing_wait = (3000 * HZ) / 100;
 }
@@ -53,3 +54,43 @@ void tty_port_free_xmit_buf(struct tty_port *port)
 EXPORT_SYMBOL(tty_port_free_xmit_buf);
 
 
+/**
+ *	tty_port_tty_get	-	get a tty reference
+ *	@port: tty port
+ *
+ *	Return a refcount protected tty instance or NULL if the port is not
+ *	associated with a tty (eg due to close or hangup)
+ */
+
+struct tty_struct *tty_port_tty_get(struct tty_port *port)
+{
+	unsigned long flags;
+	struct tty_struct *tty;
+
+	spin_lock_irqsave(&port->lock, flags);
+	tty = tty_kref_get(port->tty);
+	spin_unlock_irqrestore(&port->lock, flags);
+	return tty;
+}
+EXPORT_SYMBOL(tty_port_tty_get);
+
+/**
+ *	tty_port_tty_set	-	set the tty of a port
+ *	@port: tty port
+ *	@tty: the tty
+ *
+ *	Associate the port and tty pair. Manages any internal refcounts.
+ *	Pass NULL to deassociate a port
+ */
+
+void tty_port_tty_set(struct tty_port *port, struct tty_struct *tty)
+{
+	unsigned long flags;
+
+	spin_lock_irqsave(&port->lock, flags);
+	if (port->tty)
+		tty_kref_put(port->tty);
+	port->tty = tty;
+	spin_unlock_irqrestore(&port->lock, flags);
+}
+EXPORT_SYMBOL(tty_port_tty_set);