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WMI and the Power Management Tab

  • Artikel

Drivers that support power management can automatically enable the Power Management tab for the device property sheet in Device Manager. If a driver handles the GUID_POWER_DEVICE_ENABLE or GUID_POWER_DEVICE_WAKE_ENABLE WMI class GUIDs, Device Manager displays a Power Management tab on the device property sheet. Certain controls on the property page are enabled depending on which WMI class GUIDs the driver supports.

The GUID_POWER_DEVICE_XXX class GUIDs enable controls on the property page as follows:

  • GUID_POWER_DEVICE_ENABLE

    Enables a check box to activate or deactivate power management for the device. The data block for the WMI class consists of a single BOOLEAN value that indicates whether power management is enabled. The meaning of the value is device-dependent.

    Note

    It is generally not recommended that users modify these settings on modern standby capable systems as it can cause significant battery drain.

  • GUID_POWER_DEVICE_WAKE_ENABLE

    Enables a check box to activate or deactivate sending wait/wake IRPs. When selected, the driver should send an IRP_MN_WAIT_WAKE request to its physical device object. This enables the device to wake the system in response to an external event. This setting generally does not impact the device's ability to wake the system from modern standby but rather low power system states (Sx, where x > 0). For example, when enabled for the keyboard class driver, the keyboard device will wake the system when a key is pressed. When the check box is not selected, the driver should cancel the IRP_MN_WAIT_WAKE request. The data block for the WMI class consists of a single BOOLEAN value that indicates the current state of the check box.

WMI query requests are sent for the GUID_POWER_DEVICE_XXX WMI class GUIDs whenever the property sheet for the driver is opened in Device Manager. The WMI change requests are sent whenever one of the check box values on the Power Management tab changes. Users will expect the value they set to persist between driver loads and unloads, so drivers should store the current value of either property in the registry.

The mouse or keyboard class sample drivers both handle the GUID_POWER_DEVICE_WAKE_ENABLE WMI class GUID. See \src\input\kbdclass and \src\input\mouclass in the Windows Driver Kit (WDK).