I2C_MAJOR
i2c_dev->dev.devt = MKDEV(I2C_MAJOR, adap->nr);
res = register_chrdev_region(MKDEV(I2C_MAJOR, 0), I2C_MINORS, "i2c");
unregister_chrdev_region(MKDEV(I2C_MAJOR, 0), I2C_MINORS);
unregister_chrdev_region(MKDEV(I2C_MAJOR, 0), I2C_MINORS);