Required Dispatch Routines

Most drivers must handle the following Dispatch routines:

• DispatchPnP

  IRP_MJ_PNP indicates a request involving PnP device recognition, hardware configuration, or resource allocation. Such requests are typically sent to a device driver from the PnP manager or from a closely coupled higher-level driver.

• DispatchPower

  IRP_MJ_POWER indicates a request pertaining to the power state of either the device or the system. Such requests are sent to the device driver by either the power manager or a closely coupled higher-level driver.

• DispatchCreate

  IRP_MJ_CREATE indicates either that a user-mode protected subsystem, possibly on behalf of an application or subsystem-specific driver, has requested a handle for the file object associated with the target device object, or that a higher-level driver is connecting or attaching its device object to the target device object.

• DispatchClose

  IRP_MJ_CLOSE indicates that the last handle of the file object that was associated the target device object has been closed and released. All I/O requests have been completed or canceled, so there are no outstanding references to the file object pointer.

• DispatchRead

  IRP_MJ_READ indicates an I/O request to transfer data from the underlying physical device to the system.

• DispatchWrite

  IRP_MJ_WRITE indicates an I/O request to transfer data from the system to the underlying physical device.

• DispatchDeviceControl

  IRP_MJ_DEVICE_CONTROL indicates a request that contains a system-defined, device-type-specific I/O control code specifying a device type-specific operation. Higher-level drivers pass these IRPs on to their underlying device drivers, which typically process the request by accessing the device.

• DispatchInternalDeviceControl

  IRP_MJ_INTERNAL_DEVICE_CONTROL indicates a request sent to the device driver, in most cases from a closely coupled higher-level driver, usually with a privately defined, driver-specific and device-type-specific or device-specific I/O control code requesting a device-type-specific or device-specific operation.

  Only certain kinds of drivers are required to handle system-defined internal device I/O control requests, including certain SCSI drivers, keyboard or mouse device drivers, and parallel drivers that interoperate with system-supplied drivers.

• DispatchSystemControl

  IRP_MJ_SYSTEM_CONTROL is used to specify WMI requests to drivers. For more information about WMI, see Windows Management Instrumentation.

The dispatch routines that a driver must provide vary according to the type and functionality of the underlying physical device. For device-type-specific information about IRP major function codes that drivers must handle, see the device-type specific documentation in the Windows Driver Kit (WDK).