Irip windows9/18/2023 ![]() Return STATUS_CONTINUE_COMPLETION // Make sure of same synchronicity Because the dispatch routine is returning the status of lower driver ![]() You must not change the synchronicity of the IRP.Īs a result, there are only 2 valid versions of the completion routine in this scenario (31 and 32): NTSTATUS.You must propagate the pending status of the IRP as indicated by Irp->PendingReturned.This is to make sure that the status values set in the IRP's IoStatus block (Irp->IoStatus.Status) are the same as the return status of the lower drivers. You must not change the status of the IRP in the completion routine.If you return the status of the lower driver from your dispatch routine: Because you are setting completion routine, you must copy theĬompletionRoutine_31,// or CompletionRoutine_32 The purpose of setting the completion routine is to modify the content of the IRP on its way back. In this case, the driver sets a completion routine, forwards the IRP down, and then returns the status of lower driver as is. Scenario 3: Forward with a completion routine This is the only status you can return. KeSetEvent ((PKEVENT) Context, IO_NO_INCREMENT, FALSE) system does not have to acquire an internal lock. call KeSetEvent unnecessarily and improves performance because the You will set the event only if the lower driver has returned KernelMode, // must be Kernelmode to prevent the stack getting paged out Status = IoCallDriver(TopOfDeviceStack, Irp) You are setting completion routine, so you must copy KeInitializeEvent(&event, NotificationEvent, FALSE) You can call IoForwardIrpSynchronously to do this operation easily. For example, when you receive a IRP_MN_START_DEVICE IRP, you must forward the IRP down to the bus driver and wait for it to complete before you can start your device. This is frequently done when handling PNP IRPs. Use the following code if a driver wants to forward the IRP to a lower driver and wait for it to return so that it can process the IRP. Return IoCallDriver(TopOfDeviceStack, Irp) location because it provides better performance. You are not setting a completion routine, so just skip the stack If the driver is a top level driver, the IRP can be completed synchronously or asynchronously, depending on the status that is returned by the lower driver. The driver does not have to set a completion routine in this case. Use the following code if a driver just wants to forward the IRP down and take no additional action. Typedef enum _IO_COMPLETION_ROUTINE_RESULT IO_COMPLETION_ROUTINE_RESULT, *PIO_COMPLETION_ROUTINE_RESULT įorwarding an IRP to another driver Scenario 1: Forward and forget Completion routines can also use this enumeration instead of status codes. #define STATUS_CONTINUE_COMPLETION STATUS_SUCCESS Otherwise, STATUS_MORE_PROCESSING_REQUIRED This value should be returned from completion routines to continue If the status is anything other than STATUS_MORE_PROCESSING_REQUIRED, continue completing the IRP upward.īecause the I/O Manager does not have to know which non-STATUS_MORE_PROCESSING_REQUIRED value is used, use STATUS_SUCCESS (because the value 0 loads efficiently on most processor architectures).Īs you read the following code, note that STATUS_CONTINUE_COMPLETION is aliased to STATUS_SUCCESS in the WDK.If the status is STATUS_MORE_PROCESSING_REQUIRED, stop completing the IRP, leave the stack location unchanged and return.The I/O manager uses the following rules when it examines the status: Scenarios 6-12 discuss different ways of creating an IRP and sending it to another driver.īefore you examine the various scenarios, note that an IRP completion routine can return either STATUS_MORE_PROCESSING_REQUIRED or STATUS_SUCCESS.Scenarios 1-5 are about how to forward an IRP to a lower driver from a dispatch routine.This article discusses different ways that a driver can send IRPs to a lower driver and includes annotated sample code. A driver either creates its own IRP and sends it to a lower driver, or the driver forwards the IRPs that it receives from another driver that is attached above. A Windows Driver Model (WDM) driver typically sends input/output request packets (IRPs) to other drivers.
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