i2c: Unregister dummy devices last on adapter removal

Remove real devices first and dummy devices last. This gives device
driver which instantiated dummy devices themselves a chance to clean
them up before we do.
Signed-off-by: NJean Delvare <khali@linux-fr.org>
Tested-by: NHans Verkuil <hverkuil@xs4all.nl>
Cc: stable@kernel.org

drivers/i2c/i2c-core.c

@@ -1019,6 +1019,14 @@ static int i2c_do_del_adapter(struct i2c_driver *driver,
 }
 
 static int __unregister_client(struct device *dev, void *dummy)
+{
+	struct i2c_client *client = i2c_verify_client(dev);
+	if (client && strcmp(client->name, "dummy"))
+		i2c_unregister_device(client);
+	return 0;
+}
+
+static int __unregister_dummy(struct device *dev, void *dummy)
 {
 	struct i2c_client *client = i2c_verify_client(dev);
 	if (client)
@@ -1075,8 +1083,12 @@ int i2c_del_adapter(struct i2c_adapter *adap)
 	mutex_unlock(&adap->userspace_clients_lock);
 
 	/* Detach any active clients. This can't fail, thus we do not
-	   checking the returned value. */
+	 * check the returned value. This is a two-pass process, because
+	 * we can't remove the dummy devices during the first pass: they
+	 * could have been instantiated by real devices wishing to clean
+	 * them up properly, so we give them a chance to do that first. */
 	res = device_for_each_child(&adap->dev, NULL, __unregister_client);
+	res = device_for_each_child(&adap->dev, NULL, __unregister_dummy);
 
 #ifdef CONFIG_I2C_COMPAT
 	class_compat_remove_link(i2c_adapter_compat_class, &adap->dev,