+ if ((reg_config & 0x0f) != 0x00)
+ return -ENODEV;
+
+ /* in between, another round of sanity checks */
+ if (i2c_smbus_read_byte_data(client, 0x04) != reg_config
+ || i2c_smbus_read_byte_data(client, 0x06) != reg_config
+ || i2c_smbus_read_byte_data(client, 0xff) != reg_config)
+ return -ENODEV;
+