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When to Complete an IRP

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A driver should initiate IRP completion when any of the following conditions is met:

  • The driver determines that IRP processing cannot progress because of invalid parameters or other conditions.

  • The driver is able to handle the requested I/O operation without passing the IRP down the driver stack, and the operation has finished.

  • The IRP is being canceled. (See Canceling IRPs.)

If these conditions are not met, a driver's dispatch routine must pass the IRP down to the next-lower driver, or it must handle processing of the I/O request. If one of the conditions is met, the driver must call IoCompleteRequest.

If a driver completes a request because processing cannot progress, or if it completes a request by handling the requested operation without actually accessing the device, it typically calls IoCompleteRequest from one of its dispatch routines. For more information, see Completing IRPs in Dispatch Routines.

If a driver must access a device to satisfy the request, it typically calls IoCompleteRequest from a DpcForIsr routine. These routines are discussed extensively in Servicing Interrupts.