i2c: do not use internal data from driver core

The variable p is a data structure which is used by the driver core
internally and it is not expected that busses will be directly accessing
these driver core internal only data.
Signed-off-by: Sudip Mukherjee <sudip.mukherjee@codethink.co.uk>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
[wsa: removed the unlikely()]
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>

drivers/i2c/i2c-core.c

@@ -73,6 +73,7 @@ static struct device_type i2c_client_type;
 static int i2c_detect(struct i2c_adapter *adapter, struct i2c_driver *driver);
 
 static struct static_key i2c_trace_msg = STATIC_KEY_INIT_FALSE;
+static bool is_registered;
 
 void i2c_transfer_trace_reg(void)
 {
@@ -1529,7 +1530,7 @@ static int i2c_register_adapter(struct i2c_adapter *adap)
 	int res = 0;
 
 	/* Can't register until after driver model init */
-	if (unlikely(WARN_ON(!i2c_bus_type.p))) {
+	if (WARN_ON(!is_registered)) {
 		res = -EAGAIN;
 		goto out_list;
 	}
@@ -1926,7 +1927,7 @@ int i2c_register_driver(struct module *owner, struct i2c_driver *driver)
 	int res;
 
 	/* Can't register until after driver model init */
-	if (unlikely(WARN_ON(!i2c_bus_type.p)))
+	if (WARN_ON(!is_registered))
 		return -EAGAIN;
 
 	/* add the driver to the list of i2c drivers in the driver core */
@@ -2118,6 +2119,7 @@ static int __init i2c_init(void)
 	if (IS_ENABLED(CONFIG_OF_DYNAMIC))
 		WARN_ON(of_reconfig_notifier_register(&i2c_of_notifier));
 
+	is_registered = true;
 	return 0;
 
 class_err: