After a driver has been completely tested for configuration, all of its functionality should be thoroughly tested. This requires exercising the operation of all the driver's entry points. In addition to the basic functional tests done in configuration testing, full functionality testing requires testing the rest of the entry points and functions to obtain confidence that the driver can correctly perform all its functions.
Many drivers will require custom applications to test functionality, but basic drivers for devices such as disks, tapes, or asynchronous boards can be tested using standard system utilities. All entry points should be tested in this process, including devmap(9E), poll(9E) and ioctl(9E), if applicable. The ioctl(9E) tests might be quite different for each driver, and for nonstandard devices a custom testing application will be required.