User Control of Device Idle and Wake Behavior in UMDF

Warning

UMDF 2 is the latest version of UMDF and supersedes UMDF 1. All new UMDF drivers should be written using UMDF 2. No new features are being added to UMDF 1 and there is limited support for UMDF 1 on newer versions of Windows 10. Universal Windows drivers must use UMDF 2.

For more info, see Getting Started with UMDF.

If a device has idle power-down or wake-up capabilities, you can decide whether users should be allowed to enable or disable these capabilities.

Your UMDF-based driver can use the IWDFDevice2::AssignS0IdleSettings method to specify whether users with registry access can enable or disable a device's idle power-down capability.

Your driver can use the IWDFDevice2::AssignSxWakeSettings method to specify whether users with registry access can enable or disable a device's wake-up capability.

Both of these methods allow the driver to enable the capability, disable the capability, or give users control of the capability:

  • When a driver calls the AssignS0IdleSettings method, it can give users control of a device's idle capabilities by setting the UserControlOfIdleSettings parameter to IdleAllowUserControl and setting the Enabled parameter to WdfTrue or WdfUseDefault.

  • When a driver calls the AssignSxWakeSettings method, it can give users control of a device's wake capabilities by setting the UserControlOfWakeSettings parameter to WakeAllowUserControl and setting the Enabled parameter to WdfTrue or WdfUseDefault.

If your driver allows users to modify idle and wake settings, the framework provides a user interface, in the form of a property sheet page that Device Manager displays so that users can enable or disable the idle and wake capabilities. (The framework modifies IdleInWorkingState and WakeFromSleepState registry values. Drivers and their installation files must not read or modify these values.)

If a user modifies a device's settings, the framework updates the device's power state to match the new settings, if necessary. For example, if the user disables a device's idle power-down capability while the device is already in a low-power state because it was idle, the framework returns the device to its working state.

If your driver allows users to modify idle and wake settings, the framework enables these settings by default. Some driver writers might want to initially disable the settings before allowing users to modify them.

Therefore, versions 1.9 and later of the framework provide two driver-definable registry values, named WdfDefaultIdleInWorkingState and WdfDefaultWakeFromSleepState, which are stored in the device's Device Parameters\WDF subkey, under the device's hardware key. The values are REG_DWORD-typed, with "0" indicating the capability is disabled and "1" indicating the capability is enabled.

Your driver's INF file can use an INF AddReg directive to create and set the WdfDefaultIdleInWorkingState and WdfDefaultWakeFromSleepState registry values. For example, if your driver enables a device's idle power-down capability, but if the capability must be disabled when the device is installed, the driver's INF file can set WdfDefaultIdleInWorkingState to "0".

The framework examines the WdfDefaultIdleInWorkingState registry value only if the driver sets the UserControlOfIdleSettings parameter to IdleAllowUserControl and the Enabled parameter to WdfTrue or WdfUseDefault when the driver calls the IWDFDevice2::AssignS0IdleSettings method.

The framework examines the WdfDefaultWakeFromSleepState registry values only if the driver sets the UserControlOfWakeSettings parameter to IWakeAllowUserControl and the Enabled parameter to WdfTrue or WdfUseDefault when the driver calls the IWDFDevice2::AssignSxWakeSettings method.