What are legacy interrupts?

在看arm的trustzone的手册时，在中断一节常看到legacy interrupts这个名词，这是什么意思呢？

以下是网上高手的解释说明。

Legacy interrupts are the two interrupts that were in ARM before GIC arrived: nIRQ - normal interrupt request, and fIRQ - fast interrupt request.

Since legacy interrupts were made for single-core processors, and they don't support multi-core processors internally, the reason they bypass the distributor logic should be rather clear - the legacy interrupts are hardwired into one of the cores.

In short - it allows the CPU to work in backwards compatibility with older ARM specification. For example, a four-core ARM CPU will have 4 nIRQs and 4 fIRQs, separate for each of the cores. When you have an old piece of ARM-compatible hardware (which doesn't support GIC), you connect it to one of the core's nIRQ/fIRQ just as if you connected it to an old single-core CPU, and it will always execute on that one core.

简单说，legacy interrupts是单核时的中断中的产物，有一些早期的硬件不支持GIC，只能把中断直接连接在单核上，当项目中选用这种硬件和新的多核的处理器在一起用时，arm新的多核处理器也提供了这种legacy的硬件中断直接连接的方式，以向下兼容，这种中断无法在GIC中管理。