IoStartPacket

The IoStartPacket routine 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.

VOID 
  IoStartPacket(
    IN PDEVICE_OBJECT  DeviceObject,
    IN PIRP  Irp,
    IN PULONG  Key  OPTIONAL,
    IN PDRIVER_CANCEL  CancelFunction  OPTIONAL
    );

Parameters

DeviceObject

Pointer to the target device object for the IRP.

Irp

Pointer to the IRP to be processed.

Key

Pointer 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.

Return Value

None

Headers

Declared in wdm.h and ntddk.h. Include wdm.h or ntddk.h.

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 non-NULL 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