## Physical Device Driver Reference

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### Requesting OS/2 Services

Because many of the functions of an OS/2 device driver are related to system operations, OS/2 services are available through the DevHlp functions . Access to OS/2 services is obtained at initialization.

Some OS/2 services are limited by the context in which the physical device driver is running. See Device Helper (DevHlp) Services for a list of the DevHlp services, descriptions, and limitations.

Note: In general, DevHlp services might briefly disable processor interrupts to prevent interruptions, but preserve the entry state of the interrupt flag upon exit from the service.