е как да няма документация?
ето от Win2000 DDK (за XP-то още не се е появило):

Kernel-Mode Drivers: Windows 2000 DDK
KeRaiseIrql
VOID
KeRaiseIrql(
IN KIRQL NewIrql,
OUT PKIRQL OldIrql
);
KeRaiseIrql raises the hardware priority to a given IRQL value, thereby masking off interrupts of equivalent or lower IRQL on the current processor.

Parameters
NewIrql
Specifies the new IRQL to which the hardware priority is to be raised.
OldIrql
Pointer to the storage for the original (unraised) IRQL value to be used in a subsequent call to KeLowerIrql.
Include
wdm.h or ntddk.h

Comments
If the new IRQL is less than the current IRQL, a bug check occurs. Otherwise, the current IRQL is set to the specified value.

Callers of this routine can be running at any IRQL. Any caller should restore the original IRQL with KeLowerIrql as soon as possible.

A call to KeLowerIrql is valid if it specifies NewIrql <= CurrentIrql. A call to KeRaiseIrql is valid if the caller specifies NewIrql >= CurrentIrql.

See Also
KeGetCurrentIrql, KeLowerIrql

See Also
KeGetCurrentIrql, KeLowerIrql



но при всички положения (не само за help-a) за да напишеш driver трябва да си изтеглиш DDK-то от microsoft...