Книга: Microsoft Windows Embedded CE 6.0 Exam Preparation Kit

Shared Interrupt Mappings

Shared Interrupt Mappings

The 1:1 relationship between IRQ and SYSINTR implies that you cannot register multiple ISRs for an IRQ directly to implement interrupt sharing, but you can map multiple ISRs indirectly. The interrupt mapping tables only map an IRQ to one static ISR, yet within this ISR, you can call the NKCallIntChain function to iterate through the chain of ISRs, registered dynamically through LoadIntChainHandler. NKCallIntChain goes through the ISRs registered for the shared interrupt and returns the first SYSINTR value that is not equal to SYSINTR_CHAIN. Having determined the appropriate SYSINTR for the current interrupt source, the static ISR can pass this logical interrupt identifier to the kernel to signal the corresponding IST event. The LoadIntChainHandler function and installable ISRs are covered in more detail later in this lesson.

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