## Physical Device Driver Reference

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### Hardware Interrupt Management

The hardware interrupt handler is the component of the physical device driver that deals with a hardware interrupt. The handler is called by the OS/2 kernel when the hardware interrupt occurs, and must follow the far call/return model. By convention, the hardware interrupt handler does not need to save and restore any registers it uses because this is done by the kernel.

Before the handler can be started, its entry point must be registered for a specific hardware interrupt. This can be done during or after device driver initialization with the DevHlp_SetIRQ. Once the call to the DevHlp has been made, the hardware interrupt handler can be started.