PoRequestPowerIrp function

The PoRequestPowerIrp routine allocates a power IRP and sends it to the top driver in the device stack for the specified device.


  PDEVICE_OBJECT          DeviceObject,
  UCHAR                   MinorFunction,
  POWER_STATE             PowerState,
  __drv_aliasesMem PVOID  Context,
  PIRP                    *Irp



A pointer to the target DEVICE_OBJECT for the IRP. In Windows 2000 and later versions of Windows, this parameter can point to a physical device object (PDO) or a functional device object (FDO). In Windows 98/Me, this parameter must point to the PDO of the underlying device.


Specifies one of the following minor power IRP codes: IRP_MN_QUERY_POWER, IRP_MN_SET_POWER, or IRP_MN_WAIT_WAKE.


Specifies a POWER_STATE value to pass in the IRP. For IRP_MN_SET_POWER and IRP_MN_QUERY_POWER, specify the requested new device power state. Possible values are DEVICE_POWER_STATE values.

For IRP_MN_WAIT_WAKE, specify the lowest (least-powered) system power state from which the device should be allowed to wake the system. Possible values are SYSTEM_POWER_STATE values.


A pointer to the caller's PowerCompletion callback routine. The I/O manager calls this routine when the IRP has completed. This parameter is optional and can be set to NULL if no PowerCompletion callback routine is needed.


A pointer to a caller-supplied context to be passed through to the PowerCompletion callback. When the caller requests a device set-power IRP in response to a system set-power IRP, Context should contain the system set-power IRP that triggered the request.


A pointer to a caller-supplied variable in which PoRequestPowerIrp returns a pointer to the IRP that it allocates. Specify a value for Irp only if the MinorFunction parameter is set to IRP_MN_WAIT_WAKE. Otherwise, this parameter should always be NULL because the IRP might be completed before PoRequestPowerIrp returns, causing this parameter to point to memory that has already been discarded.

Return Value

PoRequestPowerIrp returns one of the following:

Return code Description
The IRP has been sent.
The routine could not allocate the IRP.
MinorFunction does not signify a valid minor power IRP code.


A device power policy owner calls this routine to send a wait/wake, query, or set-power IRP.

A driver calls PoRequestPowerIrp—not IoAllocateIrp—to allocate and send a power IRP that has minor IRP code IRP_MN_SET_POWER, IRP_MN_QUERY_POWER, or IRP_MN_WAIT_WAKE. (A driver must call IoAllocateIrp to send a power IRP with minor IRP code IRP_MN_POWER_SEQUENCE.)

If PoRequestPowerIrp returns a status value of STATUS_PENDING, the routine successfully allocated a device power IRP and sent it to the top of the device stack for the device. After the bus driver and all other drivers have completed the IRP, and the I/O manager has called all IoCompletion routines set by drivers as they passed the IRP down the device stack, the I/O manager calls the PowerCompletion routine and passes to this routine the specified Context value. If PoRequestPowerIrp returns a status other than STATUS_PENDING, the routine did not send a device power IRP and the PowerCompletion routine is not called.

The PowerCompletion routine performs any additional tasks the sender of the IRP requires after all other drivers have completed the IRP. It need not free the IRP; the power manager does that. In Windows 2000 and later versions of Windows, the PowerCompletion routine can be called at IRQL = PASSIVE_LEVEL or IRQL = DISPATCH_LEVEL. In Windows 98/Me, the PowerCompletion routine is always called at IRQL = PASSIVE_LEVEL, and drivers must complete IRPs at IRQL = PASSIVE_LEVEL.

A device power policy owner calls PoRequestPowerIrp to send a device query- or set-power IRP when it receives a system query- or set-power IRP. The driver should set an IoCompletion routine in the system IRP and pass the system IRP to the next lower driver. The IoCompletion routine calls PoRequestPowerIrp to send the device IRP, passing the system IRP in the Context parameter. The Context parameter is subsequently passed to the PowerCompletion routine for the device IRP. In the PowerCompletion routine, the driver can complete the system IRP. For more information, see Sending IRP_MN_QUERY_POWER or IRP_MN_SET_POWER for Device Power States and Wait/Wake Callback Routines.

Drivers can use the returned Irp to cancel an IRP_MN_WAIT_WAKE IRP. Drivers that are requesting other types of power IRPs must pass NULL for this parameter.


Windows version Available starting with Windows 2000.
Target Platform Universal
Header wdm.h (include Wdm.h, Ntddk.h, Ntifs.h)
Library NtosKrnl.lib
DLL NtosKrnl.exe
DDI compliance rules MarkDevicePower, PowerDownFail, PowerUpFail, RequestedPowerIrp, HwStorPortProhibitedDDIs

See Also