Edit

IoCompletion Routines for Wait/Wake IRPs

  • Article

The I/O manager calls a driver's wait/wake IoCompletion routine after the next-lower driver in the device stack has completed the wait/wake IRP. Each function and filter (FDO) driver that handles a wait/wake IRP should set an IoCompletion routine for the IRP.

Each function or filter driver sets an IoCompletion routine as it handles the wait/wake IRP on its way down the device stack. The device power policy owner, which sends the IRP, might therefore have an IoCompletion routine in addition to a callback routine. Keep in mind that the callback routine is invoked after the IoCompletion routine and that the two have different requirements. For more information, see Wait/Wake Callback Routines.

The actions required in a wait/wake IoCompletion routine depend on the device and the type of driver. The following are some actions a driver might need to perform in its wait/wake IoCompletion routine:

  1. Reset any relevant fields in the device extension. For example, when a wait/wake IRP is pending, most drivers set a flag and keep a pointer to the IRP in the device extension.

  2. Reset the Cancel routine, if any, for the IRP by calling IoSetCancelRoutine, specifying a NULL pointer for the routine.

  3. Call IoCompleteRequest, specifying IO_NO_INCREMENT, to complete the IRP.

As each successive driver completes the IRP, the I/O manager passes control to the IoCompletion routine of the next-higher driver going back up the stack.

After calling the IoCompletion routines set by drivers as they passed the wait/wake IRP down the device stack, the I/O manager calls the callback routine passed to PoRequestPowerIrp by the driver that sent the IRP. For further information, see Wait/Wake Callback Routines.