Writing Windows WDM Device Drivers

A new Plug and Play device has been added.
StartIo	A callback to handle IRPs serially.
Interrupt Service Routine (ISR)	Called to handle a hardware interrupt. Usually schedules a Deferred Procedure Call to do most interrupt servicing.
DpcForIsr	Deferred Procedure Call routine. Starts off another interrupt-driven transfer or completes an I/O request.
Critical section routine	Called to synchronize execution on one processor with no interrupts. Called by low IRQL tasks to interact with hardware
Cancel	Called to cancel an IRP
Completion	Called when a lower-level driver has completed processing an IRP. This lets the current driver do more work.
AdapterControl	Called when a DMA adapter channel is available.
ControllerControl	Called when a controller becomes free. NT and W2000 only.
Timer	A one-second timer callback.
CustomTimerDpc	For time-outs of less than one second.
CustomDpc	Usually used to handle work queues.
Reinitialize	Called if a driver takes a long time to initialize itself.
ConfigCallback	Query device hardware description callback. NT and W2000 only.
Plug and Play Notification	Called to notify you when devices have arrived, when the hardware profile changes, or when a device is being removed.
Callback	W2000 callback object handler

Dispatch Routines

A driver's DriverEntry routine must set up a series of callbacks for processing IRPs. It also sets the Unload, AddDevice, and StartIo routine callbacks, if these are needed. Table 2.2 shows the common Win32 device I/O functions and their corresponding IRPs. For example, a call to CreateFileends up as a create irp sent to your driver.

Table 2.2 Dispatch routine IRPs

Win32 function	IRP
CreateFile	Create IRP
CloseHandle	Close IRP
ReadFile, etc.	Read IRP
WriteFile, etc.	Write IRP
DeviceIoControl	IOCTL IRP
	Internal IOCTL IRP

One common IRP cannot be generated from user mode code[1]. The Internal IOCTL IRP can only be generated from within the kernel. This allows drivers to