Suspend and Resume Power Callbacks
Suspend and resume power callbacks are independent of the Power Manager. These callbacks occur when the OS is about to enter a suspend state in which the CPU is stopped. They are generated immediately before OEMPowerOff is invoked. Device drivers often receive Power Manager IOCTL calls before the OS suspend state that request the driver to turn itself off. This is not always the case, however. The Power Manager framework allows devices to be turned off while the OS is running or left on while the OS is suspended.
You can decide what action to take if a power-down callback is received while the device power state is D0, D1 or D2. You can often resolve this by turning the device off and then back on again when the power-up callback occurs. However, if the device can function without the CPU, it may be appropriate for you to leave the device turned on. If your device is left in a powered state during suspend, it may indicate that the Power Manager is configured incorrectly, or an application may have called SetPowerRequirement on your device using the POWER_FORCE flag.
Last updated on Tuesday, May 18, 2004
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