IOCTL_POWER_SET Request Processing (Windows CE 5.0)
The Power Manager adjusts a device's power state using the IOCTL_POWER_SET device IOCTL. Device driver developers should be aware of the following when implementing support for this IOCTL:
- Devices are not required to implement all five device power states. The only required power state is D0. Devices that only support the D0 power state will never receive IOCTL_POWER_SET.
- The Power Manager may request that the device go into any device power state, not just the ones the device claims to support in its IOCTL_POWER_CAPABILITIES handler.
- If a device is requested to go into a power state it does not support, it is expected to go into the next higher-numbered state that it does support. For example, if a device does not support D2 it should go into D3 or D4 as appropriate. The D3 state requires some special handling.
- The Power Manager may issue an IOCTL_POWER_SET that essentially puts the device into its already-current state. In this case, the device driver can simply return success and do nothing.
- The Power Manager is not required to set the device's power state to its default value as specified in a system power state. For example, if a device's power state falls into the range bounded by the system power state and application requirements the Power Manager may choose not to alter the device's power state.
See Also
Device Power Management Guidelines | IOCTL_POWER_SET | IOCTL_POWER_CAPABILITIES
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