Andi Kleen <ak@xxxxxxx> writes: > P.S.: There seems to be a lot of confusion about all this. > Maybe it would make sense to do a write up defining all the terms > and stick it into Documentation/* ? How does this look? I am pretty horrible when it comes to Documentation, but this seems to be the essence of what I was saying earlier. Eric diff --git a/Documentation/IRQ.txt b/Documentation/IRQ.txt new file mode 100644 index 0000000..5340369 --- /dev/null +++ b/Documentation/IRQ.txt @@ -0,0 +1,22 @@ +What is an IRQ? + +An IRQ is an interrupt request from a device. +Currently they can come in over a pin, or over a packet. +IRQs at the source can be shared. + +An IRQ number is a kernel identifier used to talk about a hardware +interrupt source. Typically this is an index into the global irq_desc +array, but except for what linux/interrupt.h implements the details +are architecture specific. + +An IRQ number is an enumeration of the possible interrupt sources on a +machine. Typically what is enumerated is the number of input pins on +all of the interrupt controller in the system. In the case of ISA +what is enumerated are the 16 input pins to the pair of i8259 +interrupt controllers. + +Architectures can assign additional meaning to the IRQ numbers, and +are encouraged to in the case where there is any manual configuration +of the hardware involved. The ISA IRQ case on x86 where anyone who +has been around a while can tell you how the first 16 IRQs map to the +input pins on a pair of i8259s is the classic example. - To unsubscribe from this list: send the line "unsubscribe linux-acpi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
