## Virtual Device Driver Reference for OS/2

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### Registering Virtual Device Driver for Communications

When virtual device drivers communicate with the kernel, physical device drivers, other virtual device drivers, or with the Presentation Manager interface, the Dynamic Link mechanism is used to:

Export virtual DevHlp services to virtual device drivers
Export kernel data to virtual device drivers
Export services from one virtual device driver to another

To restrict the modifications required for physical device drivers (which remain 16:16), virtual DevHlp services are provided so that a virtual device driver can establish communication with a physical device driver. This is no more than an exchange of entry points. At this point, the physical device driver and the virtual device driver can use any protocol to communicate. Although a suggested protocol is provided in Inter-Device- Driver Communication, device drivers are not restricted to this.