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

[Shu Ming <shuming@linux.vnet.ibm.com>]

IRQ number  is actually a word coming from ancient time.  When 8259 was 
popular at that time, we only have 0 ~ 15 interrupts when two 8259 are 
cascaded.  The IRQ number mattered in that time, because 8259 put their 
vector number in the bus for CPU after the interrupt was delivered.  The 
number did have special meaning to the CPU used as a vector to interrupt 
table.  However, in modern time, especially after we have APIC and MSI, 
the number don't have much meaning to CPU because the interrupt is  
targeting some special PCI address to notify the CPU.  So APIC don't 
need put a vector number in the bus. In modern os,  it is usually called 
auto vector for OS to walk the interrupt routine table.  Interrupt line 
is similar to IRQ numbers, interrupt numbers.


On 2012-3-2 20:38, Zhi Yong Wu wrote:
> HI,
>
> Can anyone explain their relationship and difference among them?  It
> is very appreciated if you can make some comments. thanks.
>


-- 
Shu Ming<shuming@linux.vnet.ibm.com>
IBM China Systems and Technology Laboratory