Input: add semaphore and user count to input_dev structure;

       serialize open and close calls and ensure that device's
       open and close methods are only called when first user
       opens it or last user closes it.

Signed-off-by: Dmitry Torokhov <dtor@mail.ru>

2 files changed, 32 insertions, 5 deletions

diff --git a/drivers/input/input.c b/drivers/input/input.c
index 3385dd03abfc..1885f369e3e2 100644
--- a/drivers/input/input.c
+++ b/drivers/input/input.c
@@ -219,10 +219,24 @@ void input_release_device(struct input_handle *handle)
 
 int input_open_device(struct input_handle *handle)
 {
+        struct input_dev *dev = handle->dev;
+        int err;
+
+        err = down_interruptible(&dev->sem);
+        if (err)
+                return err;
+
         handle->open++;
-        if (handle->dev->open)
-                return handle->dev->open(handle->dev);
-        return 0;
+
+        if (!dev->users++ && dev->open)
+                err = dev->open(dev);
+
+        if (err)
+                handle->open--;
+
+        up(&dev->sem);
+
+        return err;
 }
 
 int input_flush_device(struct input_handle* handle, struct file* file)
@@ -235,10 +249,17 @@ int input_flush_device(struct input_handle* handle, struct file* file)
 
 void input_close_device(struct input_handle *handle)
 {
+        struct input_dev *dev = handle->dev;
+
         input_release_device(handle);
-        if (handle->dev->close)
-                handle->dev->close(handle->dev);
+
+        down(&dev->sem);
+
+        if (!--dev->users && dev->close)
+                dev->close(dev);
         handle->open--;
+
+        up(&dev->sem);
 }
 
 static void input_link_handle(struct input_handle *handle)
@@ -415,6 +436,8 @@ void input_register_device(struct input_dev *dev)
 
         set_bit(EV_SYN, dev->evbit);
 
+        init_MUTEX(&dev->sem);
+
         /*
          * If delay and period are pre-set by the driver, then autorepeating
          * is handled by the driver itself and we don't do it in input.c.
diff --git a/include/linux/input.h b/include/linux/input.h
index 72731d7d189e..43e8ecec602b 100644
--- a/include/linux/input.h
+++ b/include/linux/input.h
@@ -859,6 +859,10 @@ struct input_dev {
         int (*erase_effect)(struct input_dev *dev, int effect_id);
 
         struct input_handle *grab;
+
+        struct semaphore sem;   /* serializes open and close operations */
+        unsigned int users;
+
         struct device *dev;
 
         struct list_head        h_list;