Windows® 2000 Device Driver Book: A Guide for Programmers, Second Edition, The

Writing a DpcForIsr Routine

A driver's DpcForIsr routine is responsible for determining a final status for the current request, completing the IRP, and starting the next one.

Execution Context

In response to the ISR's call to IoRequestDpc, a driver's DpcForIsr routine (described in Table 8.6) is added to the DPC dispatch queue. When the CPU's IRQL value drops below DISPATCH_LEVEL, the DPC dispatcher calls the DpcForIsr routine. A DpcForIsr routine runs at DISPATCH_LEVEL IRQL, which means it has no access to pagable addresses.

The I/O Manager ignores multiple calls to IoRequestDpc for a given device until the DpcForIsr routine executes. This is normal behavior for all DPC objects. If a driver design is such that it might issue overlapping DPC ...