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WDF_DEVICE_POWER_POLICY_IDLE_SETTINGS structure

[Applies to KMDF and UMDF]

The WDF_DEVICE_POWER_POLICY_IDLE_SETTINGS structure contains driver-supplied information that the framework uses when a device is idle and the system is in the system working state (S0).

Syntax


typedef struct _WDF_DEVICE_POWER_POLICY_IDLE_SETTINGS {
  ULONG                                 Size;
  WDF_POWER_POLICY_S0_IDLE_CAPABILITIES IdleCaps;
  DEVICE_POWER_STATE                    DxState;
  ULONG                                 IdleTimeout;
  WDF_POWER_POLICY_S0_IDLE_USER_CONTROL UserControlOfIdleSettings;
  WDF_TRI_STATE                         Enabled;
  WDF_TRI_STATE                         PowerUpIdleDeviceOnSystemWake;
  WDF_POWER_POLICY_IDLE_TIMEOUT_TYPE    IdleTimeoutType;
  WDF_TRI_STATE                         ExcludeD3Cold;
} WDF_DEVICE_POWER_POLICY_IDLE_SETTINGS, *PWDF_DEVICE_POWER_POLICY_IDLE_SETTINGS;

Members

Size

The size, in bytes, of this structure.

IdleCaps

A WDF_POWER_POLICY_S0_IDLE_CAPABILITIES-typed enumerator that identifies the device's ability to wake itself up after being set to a low-power state, while the system remains in its working (S0) state.

DxState

A DEVICE_POWER_STATE-typed enumerator that identifies the low device power state that the device will enter after the idle timeout period ends. DEVICE_POWER_STATE values are defined in wdm.h.

IdleTimeout

The amount of time, in milliseconds, that the device will remain idle before the framework places it in the DxState-supplied low-power state. To use the framework's default idle timeout value, specify IdleTimeoutDefaultValue. For more information on when the framework considers the device to be idle, see Supporting Idle Power-Down.

UserControlOfIdleSettings

A WDF_POWER_POLICY_S0_IDLE_USER_CONTROL-typed enumerator that indicates whether users have the ability to modify the device's idle settings.

Enabled

A WDF_TRI_STATE-typed enumerator that indicates whether the device will be powered down if it remains idle and while the system power is at S0. This member can have one of the following values:

WdfTrue - Powering down is enabled.

WdfFalse - Powering down is disabled.

WdfUseDefault - Powering down is initially enabled by default; but if the UserControlOfIdleSettings member is set to IdleAllowUserControl, the user's setting or driver's INF file overrides the initial value.

If powering down is enabled, the device has a wake-up capability, and the idle timeout value expires, the framework calls the driver's EvtDeviceArmWakeFromS0 callback function before the device enters a low-power state.

PowerUpIdleDeviceOnSystemWake

A WDF_TRI_STATE-typed enumerator that indicates whether the device will return to its working (D0) state when the system returns to its working (S0) state. This member is valid only if the driver sets the IdleCaps member to IdleCannotWakeFromS0. The PowerUpIdleDeviceOnSystemWake member can have one of the following values:

WdfTrue - If both the device and the system are in a low-power state, the device returns to its working state when the system returns to its working state.

WdfFalse - If both the device and the system are in a low-power state, the device remains in the low-power state when the system returns to its working state.

WdfUseDefault - The default value that the framework uses if the driver does not set a different value. This value has the same meaning as WdfFalse.

If the PowerUpIdleDeviceOnSystemWake member is set to WdfFalse or WdfUseDefault, the device returns to its working state only when software accesses the device, such as when an application sends an I/O request to the device. For more information, see A Device Returns to Its Working State.

The PowerUpIdleDeviceOnSystemWake member is available in version 1.9 and later versions of KMDF, and starting in version 2.0 of UMDF.

IdleTimeoutType

A WDF_POWER_POLICY_IDLE_TIMEOUT_TYPE-typed enumerator that indicates how the IdleTimeout member is used.

The IdleTimeoutType member is available in version 1.11 and later versions of KMDF, and starting in version 2.0 of UMDF. See additional information in Remarks.

ExcludeD3Cold

A WDF_TRI_STATE-typed enumerator that indicates whether the D3cold power state should be an allowable choice for the low-power state that the device will enter when the idle timeout period expires. The ExcludeD3Cold member can have one of the following values:

WdfTrue - The framework will move a device to a low-power D-state when the idle timeout period expires. If that D-state is D3, the device will be moved to D3hot. If ExcludeD3Cold is set to WdfTrue, then no further transition from D3hot to D3cold will be allowed.

WdfFalse - The device may enter the D3cold power state when the idle timeout period expires, if all of the following criteria are met:

  • The DxState member of this structure specifies PowerDeviceD3 or PowerDeviceMaximum.
  • The ACPI firmware indicates that the device supports the D3cold power state.
  • If the driver specified IdleCanWakeFromS0 or IdleUsbSelectiveSuspend in the IdleCaps member of this structure, the device can respond to an external wake-up event while in the D3cold power state. Otherwise, this requirement does not apply.

WdfUseDefault - The framework examines the DDInstall.HW section of the driver's INF file. If the following lines are present, this value has the same meaning as WdfFalse:

Include = machine.inf
Needs = PciD3ColdSupported

Otherwise, this value has the same meaning as WdfTrue.

The ExcludeD3Cold member is available starting in KMDF version 1.11, as well as starting in version 2.0 of UMDF, and is ignored in operating systems earlier than Windows 8. See additional information in Remarks.

Remarks

The WDF_DEVICE_POWER_POLICY_IDLE_SETTINGS structure is used as input to WdfDeviceAssignS0IdleSettings.

The first time a driver calls WdfDeviceAssignS0IdleSettings, the following actions occur:

  • The framework stores the values of all WDF_DEVICE_POWER_POLICY_IDLE_SETTINGS structure members.

  • If the UserControlOfIdleSettings member is set to IdleAllowUserControl and if the Enabled member is set to WdfUseDefault, the framework reads the registry to find out if the user has enabled powering down the device when it is idle.

During subsequent calls to WdfDeviceAssignS0IdleSettings, the framework only stores the values of the DxState, IdleTimeout, and Enabled members. Also, in KMDF 1.9 and earlier, the framework stores the value of the IdleCaps member unless the value is IdleUsbSelectiveSuspend. Therefore, the driver must use the following rules:

  • If the driver specifies IdleUsbSelectiveSuspend for the IdleCaps member's value, it must do so the first time that it calls WdfDeviceAssignS0IdleSettings, and it cannot subsequently change that value.

  • If the driver specifies IdleCanWakeFromS0 or IdleCannotWakeFromS0 the first time it calls WdfDeviceAssignS0IdleSettings, it can subsequently call WdfDeviceAssignS0IdleSettings again to change that value (but it cannot change the value to IdleUsbSelectiveSuspend).

Starting in KMDF 1.11 and UMDF 2.0, a KMDF driver can switch between IdleUsbSelectiveSuspend and IdleCannotWakeFromS0 at any time.

Starting in Windows 8, setting the IdleTimeoutType member to SystemManagedIdleTimeout or SystemManagedIdleTimeoutWithHint causes the framework to register with the power management framework (PoFx).

If the driver is implementing functional power state support for a multiple-component device, the driver must either set IdleTimeoutType to DriverManagedIdleTimeout or not call WdfDeviceAssignS0IdleSettings at all.

For more information, see Supporting Functional Power States and Overview of the Power Management Framework.

The following rules apply to the value that you specify for the DxState member:

  • The value cannot be PowerDeviceD0.

  • For USB devices, the value cannot be PowerDeviceD0 or PowerDeviceD3.

  • If you specify PowerDeviceMaximum, the framework uses the value that the driver for the device's bus supplied in the DeviceWake member of its WDF_DEVICE_POWER_CAPABILITIES structure.

  • If the value of the IdleCaps member is IdleCanWakeFromS0, you cannot specify a device power state that is lower than the device power state in the DeviceWake member of the bus driver's WDF_DEVICE_POWER_CAPABILITIES structure. (In other words, if the bus driver's DeviceWake value is PowerDeviceD2, your function driver's DxState value cannot be PowerDeviceD3.)

In operating systems earlier than Windows 8, the D3 power state signifies that the device is in a low-power state, but that some power to the bus is still maintained. Starting in Windows 8, the former D3 power state is called D3hot, and a new power state (D3cold) is available. A device can enter the D3cold state either while the system is in its working (S0) state or in a low-power state. When a device is in the D3cold power state, the bus is inactive and the device must trigger its own wake signal when an external action (for example plugging in a network cable) causes a hardware event.

Starting in KMDF 1.11 and UMDF 2.0, a device that supports idle power-down can use the ExcludeD3Cold member of this structure to specify whether the D3cold power state should be an allowable choice for the low device power state that the device will enter after the idle timeout period ends.

For information about registry entries that control a device's idle capabilities, see User Control of Device Idle and Wake Behavior.

To initialize its WDF_DEVICE_POWER_POLICY_IDLE_SETTINGS structure, your driver should call WDF_DEVICE_POWER_POLICY_IDLE_SETTINGS_INIT.

Requirements

Minimum KMDF version

1.0

Minimum UMDF version

2.0

Header

Wdfdevice.h (include Wdf.h)

 

 

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