PCI: Difference between revisions

If you plan to use the [[I/O APIC]], things aren't so easy. Basically the PCI bus specifies that their are 4 interrupt pins. They are labeled INTA#, INTB#, INTC#, and INTD#. You find out what pin a device is using by reading the ''Interrupt Pin'' field of the header. So far, so good. The only problem is that the PCI pins don't correspond to anyan particulararbitrary I/O APIC pin. It's up to the progammer to find the mapping. How is that done? You must parse the [[MP]] Tables or the [[ACPI]] tables. The MP tables are easy, only they aren't supported on newer hardware. The ACPI tables, however, involve parsing AML, which is not an easy task. If one wants to take a shortcut, you can use [[ACPICA]]. Once you've found the I/O APIC pin, all you do is map that to an IRQ using the I/O APIC redirection table. See the [[I/O APIC]] article for more information on this.

Alternatively, you could just use MSI or MSI-X, and skip all that nastycomplicated ACPI stuff.