Книга: Writing Windows WDM Device Drivers

Other PnP IRPs

Other PnP IRPs

This section briefly describes the Plug and Plug minor function code IRPs that have not been described in full before. These IRPs are handled by PnP bus drivers. The notes for each function code indicate if it is possible for a function driver to intercept the IRP.

Most function drivers ignore all these PnP IRPs. However, a function driver that performs Power Management may well want to handle IRP_MN_QUERY_CAPABILITIES. The following chapter describes how this is done.

This message tells a driver if its device is in the path of a paging, hibernation, or crash dump file. Do not allow a device to be removed until you are notified that no critical file is on its path.

The Windows 2000 PnP Manager sends this IRP to a device stack so filter and function drivers can adjust the resources required by the device, if appropriate. Function, filter, and bus drivers can handle this request.

The PnP Manager uses this IRP to request the type and instance number of a device's parent bus.

Bus drivers should handle this request for their child devices (PDOs). Function and filter drivers do not handle this IRP.

The PnP Manager sends this IRP to get the capabilities of a device, such as whether the device can be locked or ejected, and various Power Management features. Function and filter drivers can handle this request if they alter the capabilities supported by the bus driver. Bus drivers must handle this request for their child devices.

This IRP is sent twice, both before and after function drivers are loaded and started.

A driver can send one of these IRPs down the stack to see what the bus driver capabilities are.

This IRP asks how this device relates to other devices and comes in five different forms. All forms return an array of pointers to the relevant PDOs.

A BusRelations query asks for the PDOs of all the devices physically present on the bus. EjectionRelations asks which devices are also ejected if this device is ejected. PowerRelations asks which devices are also powered down when this device is powered down. RemovalRelations asks which devices must be removed when this device is removed. TargetDeviceRelation calls ObReferenceObject for the device PDO and returns the PDO.

The PnP Manager uses this IRP to get a device's description or location information. Bus drivers must handle this request for their child devices if the bus supports this information. Function and filter drivers do not handle this IRP.

Parameters.QueryDeviceText.DeviceTextType is either DeviceTextDescription or DeviceTextLocationInformation.Parameters.QueryDeviceText.LocaleId is an LCID specifying the locale for the requested text.

This IRP gets device, hardware, compatible, or instance IDs for a device, depending on whether Parameters.QueryId.IdType is BusQueryDeviceID, BusQueryHardwareIDs, BusQueryCompatibleIDs, or BusQueryInstanceID.

The IRP_MN_QUERY_INTERFACE request enables a driver to export a direct-call interface to other drivers.

The query asks the drivers in the device stack to set any of the state bits shown in Table 9.3. Be careful not to overwrite any bits that are set by other drivers.

Table 9.3 Query device state bits

If any of the state characteristics change after the initial query, a driver notifies the PnP Manager by calling IoInvalidateDeviceState. In response to a call to IoInvalidateDeviceState, the PnP Manager queries the device's PNP_DEVICE_STATE again.

The PnP Manager uses this IRP to get a device's resource requirements list. Bus drivers must handle this request for their child devices that require hardware resources. Function and filter drivers do not handle this IRP.

The PnP Manager uses this IRP to get a device's boot configuration resources. Bus drivers must handle this request for their child devices that require hardware resources. Function and filter drivers do not handle this IRP.

Bus drivers for buses with configuration space must return the relevant information for their child devices. Filter and function drivers do not handle this request.

This request is used to lock or unlock a device. Bus drivers must handle this IRP for a child device that supports device locking. Function and filter drivers do not handle this request.

Bus drivers must write the given information into the configuration space of the child device. Function and filter drivers do not handle this request.

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