i2c: Use the driver model reference counting

Don't implement our own reference counting mechanism for i2c clients
when the driver model already has one.

Signed-off-by: Jean Delvare <[e-mail]>
Cc: David Brownell <[e-mail]>

drivers/i2c/i2c-core.c

···
 	}
 	list_add_tail(&client->list,&adapter->clients);
 
-	client->usage_count = 0;
-
 	client->dev.parent = &client->adapter->dev;
 	client->dev.bus = &i2c_bus_type;
 
···
 	struct i2c_adapter *adapter = client->adapter;
 	int res = 0;
 
-	if (client->usage_count > 0) {
-		dev_warn(&client->dev, "Client [%s] still busy, "
-			 "can't detach\n", client->name);
-		return -EBUSY;
-	}
-
 	if (adapter->client_unregister)  {
 		res = adapter->client_unregister(client);
 		if (res) {
···
 }
 EXPORT_SYMBOL(i2c_detach_client);
 
-static int i2c_inc_use_client(struct i2c_client *client)
-{
-
-	if (!try_module_get(client->driver->driver.owner))
-		return -ENODEV;
-	if (!try_module_get(client->adapter->owner)) {
-		module_put(client->driver->driver.owner);
-		return -ENODEV;
-	}
-
-	return 0;
-}
-
-static void i2c_dec_use_client(struct i2c_client *client)
-{
-	module_put(client->driver->driver.owner);
-	module_put(client->adapter->owner);
-}
-
 int i2c_use_client(struct i2c_client *client)
 {
-	int ret;
-
-	ret = i2c_inc_use_client(client);
-	if (ret)
-		return ret;
-
-	client->usage_count++;
-
+	get_device(&client->dev);
 	return 0;
 }
 EXPORT_SYMBOL(i2c_use_client);
 
 int i2c_release_client(struct i2c_client *client)
 {
-	if (!client->usage_count) {
-		pr_debug("i2c-core: %s used one too many times\n",
-			 __FUNCTION__);
-		return -EPERM;
-	}
-
-	client->usage_count--;
-	i2c_dec_use_client(client);
-
+	put_device(&client->dev);
 	return 0;
 }
 EXPORT_SYMBOL(i2c_release_client);

drivers/media/video/ks0127.c

···
 	.addr = 0,
 	.adapter = NULL,
 	.driver = &i2c_driver_ks0127,
-	.usage_count = 0
 };
 
 static int ks0127_found_proc(struct i2c_adapter *adapter, int addr, int kind)

include/linux/i2c.h

···
  *	generic enough to hide second-sourcing and compatible revisions.
  * @adapter: manages the bus segment hosting this I2C device
  * @driver: device's driver, hence pointer to access routines
- * @usage_count: counts current number of users of this client
  * @dev: Driver model device node for the slave.
  * @irq: indicates the IRQ generated by this device (if any)
  * @driver_name: Identifies new-style driver used with this device; also
···
 	char name[I2C_NAME_SIZE];
 	struct i2c_adapter *adapter;	/* the adapter we sit on	*/
 	struct i2c_driver *driver;	/* and our access routines	*/
-	int usage_count;		/* How many accesses currently  */
-					/* to the client		*/
 	struct device dev;		/* the device structure		*/
 	int irq;			/* irq issued by device (or -1) */
 	char driver_name[KOBJ_NAME_LEN];