关于设备电源状态D3的问题

[huangbt_amoi]

为什么可以把系统从挂起状态的设备不能通过DevicePowerNotify申请进入D3状态呢？
小弟看了windows mobile 5.0的文档，但是看得一头雾水，请各位大哥大姐指教，本人不胜感激！以下是mobile的部分文档：

Devices that can wake the system from a suspend state should not request the D3 state through DevicePowerNotify. This is because enabling a device as a wake source is not always appropriate, unless the system is going to enter a suspend state. The driver cannot distinguish IOCTL_POWER_SET requests for D3 that it has initiated itself from those initiated by the Power Manager as part of a system power state transition.

If a non-wake-enabled device is in D3 and the system suspends, it should transition to D4 in its XXX_PowerDown (Device Manager) handler and back to D3 in its XXX_PowerUp (Device Manager) handler. If it cannot do this, it should not attempt to support D3, but should transition to D4 when requested to go into D3.

[tong20037]

路过～

[huangbt_amoi]

快回复啊，在线等！

[huangbt_amoi]

急啊，急！！！！

[huangbt_amoi]

自己顶

[Mobile_Writer]

可以通过
SetDevicePower（）
来实现。
或者也试试SetSystemPowerState（）
来试试。
正常情况下D0到D4是如下定义的，但有的时候不一定，有OEM决定。
//*****************************************************************************
// T Y P E D E F S
//*****************************************************************************

//
// Device Power States
//
typedef enum _CEDEVICE_POWER_STATE {
PwrDeviceUnspecified = -1,
D0 = 0, // Full On: full power, full functionality
D1, // Low Power On: fully functional at low power/performance
D2, // Standby: partially powered with automatic wake
D3, // Sleep: partially powered with device initiated wake
D4, // Off: unpowered
PwrDeviceMaximum
} CEDEVICE_POWER_STATE, *PCEDEVICE_POWER_STATE;

[huangbt_amoi]

多谢楼上老兄，但我不是问如何让设备进入D3状态，而是为什么可以作为唤醒源的设备不要通过DevicePowerNotify申请进入D3状态，也就是：Devices that can wake the system from a suspend state should not request the D3 state through DevicePowerNotify
后面解释了原因：This is because enabling a device as a wake source is not always appropriate。但是这好像说得太含糊了吧！能不能给点详细点的解释？

[huangbt_amoi]

郁闷了，这么多天，没人帮我解决