Re: [Qemu-devel] IRQ number, interrupt number, interrupt line & GPIO[in/out]

[陳韋任 <chenwj@iis.sinica.edu.tw>]

> Can anyone explain their relationship and difference among them?  It
> is very appreciated if you can make some comments. thanks.

  I think IRQ number, interrupt number are quite similar things. You can
check PIC [1] first, especially 8259A [2]. When a device raise an interrupt,
the interrupt is delivered to CPU through PIC. Each device attaches itself
to one of PIC's pins. Thus, when we say the IRQ number of device X is Y,
it means device X attaches itself to PIC's pin Y. PIC will deliver the highest
priority interrupt to the CPU. The term "interrupt line" might appear in PCI
context [3]. BIOS usually uses interrupt line to represent what PIC pin the
device attatches to. Note that PIC (Programmable Interrupt Controller) and
PCI (Peripheral Component Interconnect) are different things.

  GPIO mostly is used on SoC. It depends on the vendor how to use GPIO. One
of GPIO capabilities is similar to PIC, I guess. But I leave this to SoC
experts. I strongly recommend the book [5] if you want to learn how things
work.

HTH, 
chenwj

[1] http://en.wikipedia.org/wiki/Programmable_Interrupt_Controller
[2] http://en.wikipedia.org/wiki/Intel_8259
[3] http://en.wikipedia.org/wiki/Conventional_PCI
[4] http://en.wikipedia.org/wiki/General_Purpose_Input/Output
[5] 系统虚拟化:原理与实现

-- 
Wei-Ren Chen (陳韋任)
Computer Systems Lab, Institute of Information Science,
Academia Sinica, Taiwan (R.O.C.)
Tel:886-2-2788-3799 #1667
Homepage: http://people.cs.nctu.edu.tw/~chenwj