After a driver has been completely tested for configuration, all of the driver's functionality should be thoroughly tested. These tests require exercising the operation of all of the driver's entry points.
Many drivers require custom applications to test functionality. However, 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), chpoll(9E), and ioctl(9E), if applicable. The ioctl() tests might be quite different for each driver. For nonstandard devices, a custom testing application is generally required.