As a course of learning linux device drivers, I'm implementing a PCIe driver, and I'd like to understand at what level the interrupts can be or should be enabled/disabled. I intentionally do not specify OS, as I'm assuming it should be relevant for any platform. By levels I mean the following:
a) OS specific interrupts handling framework
b) Interrupts can be disabled or enabled in the PCI/PCIe configuration space registers, e.g. COMMAND register
c) Interrupts also can be masked at device level, for instance we can configure device not trigger certain interrupts to the host
I understand that whatever interrupt type is being used on PCIe (INTx emulation, MSI or MSI-X), it has to be delivered to the host OS. So my question is really -- do we actually have to enable or disable interrupts on every layer, or it's sufficient only at the closest to hardware, e.g. in relevant PCI registers?