## Storage Device Driver Reference

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### Presence-Check Function

A presence-check function is a Ring 3 (nonprivileged) EXE program that determines whether a given hardware interface is present on a workstation. The module returns 0 when the specific interface is detected and 1 when the interface is not detected. For these modules to identify installed OEM adapters, Ring 0 services are provided by the device driver TESTCFG.SYS. TESTCFG provides the following IOCtl services for OEM adapter presence- check modules:

Determines CPU host bus type
Reads adapter ROM space
Executes IN/OUT instruction
Reads EISA adapter IDs

Refer to the OS/2 Physical Device Driver Reference for details on the TESTCFG device driver services.

Note: Be sure to write adapter presence-check modules to avoid disruption or conflicts with other installed host adapters.