IoStartPacket

VOID
    IoStartPacket(
        IN PDEVICE_OBJECT  DeviceObject,
        IN PIRP  Irp,
        IN PULONG  Key,                /* optional */
        IN PDRIVER_CANCEL  CancelFunction     /* optional */
        );

IoStartPacket calls the driver’s StartIo routine with the given IRP or inserts the IRP into the device queue associated with the given device object if the device is already busy.

Parameters

DeviceObject

Points to the target device object for the IRP.

Irp

Points to the IRP to be processed.

Key

Points to a value that determines where to insert the packet into the device queue. If this is zero, the packet is inserted at the tail of the device queue.

CancelFunction

Specifies the entry point for a driver-supplied Cancel routine.

Comments

If the driver is already busy processing a request for the target device object, then the packet is queued in the device queue. Otherwise, this routine calls the driver’s StartIo routine with the specified IRP.

If a nonNULL CancelFunction pointer is supplied, it is set in the IRP so the driver’s Cancel routine is called if the IRP is canceled before its completion.

Drivers that do not have a StartIo routine cannot call IoStartPacket.

Callers of IoStartPacket must be running at IRQL <= DISPATCH_LEVEL. Usually, this routine is called from a device driver’s Dispatch routine at IRQL PASSIVE_LEVEL.

See Also

DEVICE_OBJECT, IoMarkIrpPending, IoSetCancelRoutine, IoStartNextPacket, IoStartNextPacketByKey