EvtDeviceD0Entry

EvtDeviceD0Entry is a callback function in the Windows Driver Model (WDM) and Windows Driver Frameworks (WDF) that a device driver implements to handle the transition of a device into the D0 power state. The D0 state is the fully powered-on state where the device is operational. When the operating system determines that a device needs to be powered up, it calls the driver's EvtDeviceD0Entry function.

This function is responsible for performing any necessary hardware initialization, re-enabling hardware interrupts, and ensuring the device is ready to accept I/O operations. It might involve programming specific registers on the device, verifying hardware presence, or restoring configuration settings that were saved when the device entered a lower power state. The function receives a WDFDEVICE handle (for WDF drivers) or a PDEVICE_OBJECT pointer (for WDM drivers) and a WDF_POWER_DEVICE_STATE enumeration value indicating the target power state, which in this case will be WdfPowerDeviceD0.

If the driver successfully prepares the device for the D0 state, EvtDeviceD0Entry should return a success status code, such as STATUS_SUCCESS. If an error occurs during the initialization process, the driver should return an appropriate error code, and the system will attempt to handle the failure, potentially by transitioning the device to a lower power state. This callback is crucial for proper device power management and ensures that devices are functional when needed.