PnP Driver Design Guidelines

Plug and Play provides:

• Automatic and dynamic recognition of installed hardware

• Hardware resource allocation (and reallocation)

• Loading of appropriate drivers

• An interface for drivers to interact with the PnP system

• Mechanisms for drivers and applications to learn of changes in the hardware environment

To support PnP, a driver must follow these guidelines:

• It must contain a DispatchPnP routine.

  This dispatch routine must handle IRP_MJ_PNP requests and associated minor function codes. For more information, see DispatchPnP Routines.

• It must not search for hardware.

  The PnP manager is responsible for determining the presence of hardware devices. When the PnP manager detects a device, it notifies the driver by calling its AddDevice routine. Hardware can be detected when the system is booted, or any time that a user adds a device to, or removes one from, a running system.

• It must not allocate hardware resources.

  A PnP driver must provide the PnP manager with lists of resources that a device can potentially use. The PnP manager is responsible for assigning resources to each device, and notifying the driver of each device's assignments when it sends an IRP_MN_START_DEVICE request. The driver must thus be capable of working with various configurations of hardware resources.

Some drivers are insulated from the details of the PnP and power management by system-supplied port or class drivers. For example, a SCSI port driver insulates a SCSI miniport driver from many of the details of the power and PnP systems, so a SCSI miniport driver does not need to handle power and PnP IRPs directly. For such drivers, see the driver-specific documentation for details of the required PnP support.