Installing a Null Driver

You might install a "null driver" (that is, nonexistent driver) for a device if the device is not used on the machine and should not be started. Such devices do not typically exist on a machine, but if they do, you can install a null driver. Additionally, the system installs null drivers for devices that do not have a function driver, if they are capable of executing in raw mode.

To specify a null driver in an INF file, use entries like the following:

%MyDeviceDescription% = MyNullInstallSection, &BadDeviceHardwareID%

; The install section is typically empty, but can contain entries that
; copy files or modify the registry.

AddService = ,2    ; no value for the service name

The hardware ID for the device in the Models section should identify the device specifically, using the subsystem vendor ID and whatever other information is relevant.

The operating system will create a device node (devnode) for the device, but if the device is not capable of executing in raw mode, the operating system will not start the device because a function driver has not been assigned to it. Note, however, that if the device has a boot configuration, those resources will be reserved.



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