Input: serio_raw - explicitly mark disconnected ports as dead

Instead of relying on setting serio_raw->serio to NULL upon disconnecting
ports mark them explicitly as "dead". Also take and carry reference to
underlying serio port to make sure it does not go away until we are done
with it.
Reviewed-by: Wanlong Gao <gaowanlong@cn.fujitsu.com>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>

drivers/input/serio/serio_raw.c

@@ -40,6 +40,7 @@ struct serio_raw {
 	wait_queue_head_t wait;
 	struct list_head client_list;
 	struct list_head node;
+	bool dead;
 };
 
 struct serio_raw_client {
@@ -91,7 +92,7 @@ static int serio_raw_open(struct inode *inode, struct file *file)
 		goto out;
 	}
 
-	if (!serio_raw->serio) {
+	if (serio_raw->dead) {
 		retval = -ENODEV;
 		goto out;
 	}
@@ -123,6 +124,8 @@ static void serio_raw_cleanup(struct kref *kref)
 
 	misc_deregister(&serio_raw->dev);
 	list_del_init(&serio_raw->node);
+
+	put_device(&serio_raw->serio->dev);
 	kfree(serio_raw);
 }
 
@@ -164,19 +167,18 @@ static ssize_t serio_raw_read(struct file *file, char __user *buffer,
 	char uninitialized_var(c);
 	ssize_t retval = 0;
 
-	if (!serio_raw->serio)
+	if (serio_raw->dead)
 		return -ENODEV;
 
 	if (serio_raw->head == serio_raw->tail && (file->f_flags & O_NONBLOCK))
 		return -EAGAIN;
 
 	retval = wait_event_interruptible(serio_raw->wait,
-					  serio_raw->head != serio_raw->tail ||
-						!serio_raw->serio);
+			serio_raw->head != serio_raw->tail || serio_raw->dead);
 	if (retval)
 		return retval;
 
-	if (!serio_raw->serio)
+	if (serio_raw->dead)
 		return -ENODEV;
 
 	while (retval < count && serio_raw_fetch_byte(serio_raw, &c)) {
@@ -201,7 +203,7 @@ static ssize_t serio_raw_write(struct file *file, const char __user *buffer,
 	if (retval)
 		return retval;
 
-	if (!serio_raw->serio) {
+	if (serio_raw->dead) {
 		retval = -ENODEV;
 		goto out;
 	}
@@ -291,10 +293,12 @@ static int serio_raw_connect(struct serio *serio, struct serio_driver *drv)
 	snprintf(serio_raw->name, sizeof(serio_raw->name),
 		 "serio_raw%d", serio_raw_no++);
 	kref_init(&serio_raw->kref);
-	serio_raw->serio = serio;
 	INIT_LIST_HEAD(&serio_raw->client_list);
 	init_waitqueue_head(&serio_raw->wait);
 
+	serio_raw->serio = serio;
+	get_device(&serio->dev);
+
 	serio_set_drvdata(serio, serio_raw);
 
 	err = serio_open(serio, drv);
@@ -330,6 +334,7 @@ static int serio_raw_connect(struct serio *serio, struct serio_driver *drv)
 	list_del_init(&serio_raw->node);
 out_free:
 	serio_set_drvdata(serio, NULL);
+	put_device(&serio->dev);
 	kfree(serio_raw);
 out:
 	mutex_unlock(&serio_raw_mutex);
@@ -365,7 +370,7 @@ static void serio_raw_disconnect(struct serio *serio)
 	serio_close(serio);
 	serio_set_drvdata(serio, NULL);
 
-	serio_raw->serio = NULL;
+	serio_raw->dead = true;
 	wake_up_interruptible(&serio_raw->wait);
 	kref_put(&serio_raw->kref, serio_raw_cleanup);