From a6b37451a52ae7d30c2493b9cc14b8604e81587d Mon Sep 17 00:00:00 2001
From: mokopatches <mokopatches@openmoko.org>
Date: Sun, 13 Apr 2008 07:23:53 +0100
Subject: [PATCH] fix-EVIOCGRAB-semantics.patch

---
 drivers/input/evdev.c |   32 +++++++++++++++-----------------
 1 files changed, 15 insertions(+), 17 deletions(-)

diff --git a/drivers/input/evdev.c b/drivers/input/evdev.c
index e5b4e9b..2f3d825 100644
--- a/drivers/input/evdev.c
+++ b/drivers/input/evdev.c
@@ -28,7 +28,7 @@ struct evdev {
 	char name[16];
 	struct input_handle handle;
 	wait_queue_head_t wait;
-	struct evdev_client *grab;
+	int *grab;
 	struct list_head client_list;
 	spinlock_t client_lock; /* protects client_list */
 	struct mutex mutex;
@@ -39,6 +39,7 @@ struct evdev_client {
 	struct input_event buffer[EVDEV_BUFFER_SIZE];
 	int head;
 	int tail;
+	int grab;
 	spinlock_t buffer_lock; /* protects access to buffer, head and tail */
 	struct fasync_struct *fasync;
 	struct evdev *evdev;
@@ -79,12 +80,8 @@ static void evdev_event(struct input_handle *handle,
 
 	rcu_read_lock();
 
-	client = rcu_dereference(evdev->grab);
-	if (client)
+	list_for_each_entry_rcu(client, &evdev->client_list, node)
 		evdev_pass_event(client, &event);
-	else
-		list_for_each_entry_rcu(client, &evdev->client_list, node)
-			evdev_pass_event(client, &event);
 
 	rcu_read_unlock();
 
@@ -135,14 +132,15 @@ static int evdev_grab(struct evdev *evdev, struct evdev_client *client)
 {
 	int error;
 
-	if (evdev->grab)
+	if (client->grab)
 		return -EBUSY;
 
-	error = input_grab_device(&evdev->handle);
-	if (error)
-		return error;
-
-	rcu_assign_pointer(evdev->grab, client);
+	if (!evdev->grab++) {
+	    error = input_grab_device(&evdev->handle);
+	    if (error)
+		    return error;
+	}
+	client->grab = 1;
 	synchronize_rcu();
 
 	return 0;
@@ -150,12 +148,12 @@ static int evdev_grab(struct evdev *evdev, struct evdev_client *client)
 
 static int evdev_ungrab(struct evdev *evdev, struct evdev_client *client)
 {
-	if (evdev->grab != client)
+	if (!client->grab)
 		return  -EINVAL;
 
-	rcu_assign_pointer(evdev->grab, NULL);
-	synchronize_rcu();
-	input_release_device(&evdev->handle);
+	if (!--evdev->grab && evdev->exist)
+		input_release_device(&evdev->handle);
+	client->grab = 0;
 
 	return 0;
 }
@@ -230,7 +228,7 @@ static int evdev_release(struct inode *inode, struct file *file)
 	struct evdev *evdev = client->evdev;
 
 	mutex_lock(&evdev->mutex);
-	if (evdev->grab == client)
+	if (client->grab)
 		evdev_ungrab(evdev, client);
 	mutex_unlock(&evdev->mutex);
 
-- 
1.5.6.5