values from pci_dev or read from config space - pci

[Oscar Salvador]

Thanks ;)! I didn't find it.

Kind regards

2014-08-26 15:39 GMT+02:00  <Valdis.Kletnieks at vt.edu>:
> On Tue, 26 Aug 2014 08:33:18 +0200, Oscar Salvador said:
>
>> If I get the IRQ from the pci_dev, I get a X, but if I get the IRQ
>> from the config space, I get another different number Y.
>>
>> Would be you so kind to explain:
>>
>> 1- Why it's better use the values stored in pci_dev structure instead
>> of read from config space.
>> 2- Why the IRQ number is different? (Maybe this question is answered
>> with the first question hehe)
>
> The Linux kernel keeps track of both physical and logical IRQ numbers.
> So physical IRQ 0 is often wired to a timer on x86 systems, but logical
> IRQ 0 is used for NO_IRQ  in dev->irq  type usages.
>
> Screw it, I'll let Linus explain from a decade ago:
>
> http://yarchive.net/comp/linux/no_irq.html