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IRP_MN_SET_POWER

This IRP notifies a driver of a change to the system power state or sets the device power state for a device.

Major Code

IRP_MJ_POWER

When Sent

Either the system power manager or a device power policy owner can send this IRP.

The power manager sends this IRP to notify drivers of a change to the system power state. If a driver has registered its device for idle detection, the power manager sends this IRP to change the power state of an idle device.

A driver that owns power policy sends this IRP to set the device power state for its device. A driver must call PoRequestPowerIrp to send this IRP.

The power manager sends this IRP at IRQL = PASSIVE_LEVEL to device stacks that set the DO_POWER_PAGABLE flag in the PDO. Drivers in such stacks can touch paged code or data to complete the request.

The power manager can send the IRP at IRQL = DISPATCH_LEVEL if the DO_POWER_INRUSH flag is set. Such drivers cannot directly or indirectly access any paged code or data.

Input Parameters

The Parameters.Power.Type member specifies the type of power state being set, either SystemPowerState or DevicePowerState.

The Parameters.Power.State member specifies the power state itself, as follows:

  • If Parameters.Power.Type is SystemPowerState, the value is an enumerator of the SYSTEM_POWER_STATE type.

  • If Parameters.Power.Type is DevicePowerState, the value is an enumerator of the DEVICE_POWER_STATE type.

The Parameters.Power.ShutdownType member specifies additional information about the requested transition. The possible values for this member are POWER_ACTION enumeration values. For more information, see System Power Actions.

Starting with Windows Vista, the Parameters.Power.SystemPowerStateContext member is a read-only, partially opaque SYSTEM_POWER_STATE_CONTEXT structure that contains information about the previous system power states of a computer. If Parameters.Power.Type is SystemPowerState and Parameters.Power.State is PowerSystemWorking, two flag bits in this structure indicate whether a fast startup or a wake-from-hibernation caused the computer to enter the S0 (working) system state. For more information, see Distinguishing Fast Startup from Wake-from-Hibernation.

Output Parameters

Parameters.Power.SystemContext is reserved for system use.

I/O Status Block

A driver sets Irp->IoStatus.Status to STATUS_SUCCESS to indicate that the device has entered the requested state.

A driver must not fail a request to set the system power state.

Function and filter drivers that are located above a bus driver must not fail a request to set a device power state. The bus driver can fail a device power-up request if the device is removed or in the process of being removed.

Operation

The power manager or a driver can request an IRP_MN_SET_POWER IRP. The power manager sends this IRP for one of the following reasons:

  • To notify drivers of a change to the system power state

  • To change the power state of a device for which the power manager is performing idle detection

A driver that owns device power policy sends IRP_MN_SET_POWER to change the power state of its device.

At any given time, the system allows only one such IRP to be active for each device object.

Each driver must pass each power IRP down to the next-lower driver by calling IoCallDriver (starting with Windows Vista) or PoCallDriver (Windows Server 2003, Windows XP, and Windows 2000). The PoCallDriver interface is similar to that of IoCallDriver, except that the power management subsystem might delay the IRP before passing it on to the next driver. For example, delays can occur on a PowerDeviceD0 request if the device requires inrush current and therefore must be powered up serially with another such device.

After a driver receives an IRP_MN_SET_POWER request on Windows Server 2003, Windows XP, or Windows 2000, a driver must call PoStartNextPowerIrp, as described in Calling PoStartNextPowerIrp. Beginning with Windows Vista, calling PoStartNextPowerIrp is not required, and such a call performs no power management operation.

IRP_MN_SET_POWER for System Power States

Only the system power manager can send a system set-power IRP.

A driver must not fail a request to set the system power state.

Whenever possible, the power manager sends IRP_MN_QUERY_POWER before sending IRP_MN_SET_POWER to request a system sleep state. However, under some conditions (such as the user pressing the Power Off button or a battery expiring), the power manager might issue IRP_MN_SET_POWER without first querying. The power manager queries only for sleep states; it never queries before powering up.

The IRP_MN_SET_POWER request is sent to the top driver in the device stack for a device. The top driver passes the IRP down to the next lower driver and so forth until the IRP reaches the bus driver, which must complete the IRP.

A filter driver typically does not need to act on a system set-power IRP, other than to pass it on.

The device power policy owner, however, sets an IoCompletion routine before passing down the IRP. In the IoCompletion routine, it sends an IRP_MN_SET_POWER request for a device power IRP. For more information, see Handling a System Set-Power IRP in a Device Power Policy Owner.

A system set-power IRP informs drivers that a change to the system power state is imminent and the drivers must prepare for it. However, a driver should not change the power state of its device until it receives an IRP_MN_SET_POWER for a device power state.

The value at Parameters.Power.ShutdownType provides additional information about the pending actions. When the IRP specifies PowerSystemShutdown (S5), a driver can determine whether the system is resetting (PowerActionShutdownReset) or powering off indefinitely to reboot later (PowerActionShutdownOff). For drivers of most devices, the difference is inconsequential. However, for certain devices, such as video streaming devices, a driver might power off the device in order to stop I/O when the system is resetting.

On Windows 2000 and later versions of the operating system, the value at ShutdownType can also be PowerActionShutdown. In this case, the driver cannot tell what type of shutdown is requested and should therefore proceed as for a reset.

Device Power States

Function and filter drivers that are located above a bus driver must not fail a request to set a device power state. The bus driver can fail a device power-up request if the device is removed or in the process of being removed.

A driver must set the device into the requested state before completing the IRP.

When the IRP requests a transition to a lower power state, drivers must handle the IRP as it travels down the device stack, saving any context the driver will need to restore the device to the working state. After a bus driver receives an IRP, the driver:

  • Saves any context the driver will need to restore the device to the working state.

  • Sets the device to the requested power state.

  • Calls PoSetPowerState to notify the power manager.

  • Calls PoStartNextPowerIrp to start the next power IRP (Windows Server 2003, Windows XP, and Windows 2000 only).

  • Completes the device power IRP.

The driver must complete this IRP in a timely manner. In general, drivers should avoid any delay that a typical user would find noticeably slow. For example, a driver could delay a system state change to flush cached disk or network data, but should not keep a network connection alive or format a tape. For more information, see Passing Power IRPs.

On Windows 2000 and later versions of the operating system, if the IRP specifies PowerDeviceD1, PowerDeviceD2, or PowerDeviceD3, and a system set-power IRP is active, the value at Parameters.Power.ShutdownType provides information about the system IRP.

Drivers of devices on the hibernate path should inspect this value. If the IRP requests PowerDeviceD3 and ShutdownType is PowerActionHibernate, such a driver should save any context required to restore the device, but should not power down the device; the device will enter the D3 state when the machine loses power.

On Windows 2000 and later versions of the operating system, drivers should not rely on the value at ShutdownType if the requested power state is PowerDeviceD0.

On Windows 98/Me, if the IRP requests a device power state, the ShutdownType is always PowerActionNone.

The driver that determines when to power down a device varies depending on the device class.

The driver that determines when to power up a device is almost always a driver that accesses the device registers. The driver must verify that the device is in the D0 state before accessing the device's hardware registers. If the device is not in the D0 state, the driver must call PoRequestPowerIrp to send an IRP to power up the device. A driver cannot access its device unless the device is in the D0 state.

When a driver receives a set-power IRP for device state D0, it sets an IoCompletion routine and passes the IRP to the next lower driver.

When the IRP reaches the bus driver, that driver applies (or resets) power to the device, calls PoStartNextPowerIrp (Windows Server 2003, Windows XP, and Windows 2000 only), and calls PoSetPowerState to inform the power manager of the new power state for the device.

After the bus driver completes the power-up IRP, function and filter drivers handle the IRP in their IoCompletion routines as it travels back up the device stack. In the IoCompletion routine, each driver restores or reinitializes its device context and performs any other required start-up tasks.

For more information, see Handling IRP_MN_SET_POWER for Device Power States.

Requirements

Header

Wdm.h (include Wdm.h, Ntddk.h, or Ntifs.h)

See also

DEVICE_POWER_STATE
IoCallDriver
IRP_MN_QUERY_POWER
IRP_MN_SET_POWER
PoCallDriver
PoStartNextPowerIrp
PoSetPowerState
PoRequestPowerIrp
SYSTEM_POWER_STATE
SYSTEM_POWER_STATE_CONTEXT

 

 

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