On Mon, Dec 14, 2009 at 10:23:39AM +0100, Magnus Christensson wrote: >> This function implement the same logic as pci_swizzle_interrupt_pin() in >> Linux kernel. This logic defines how PCI bridge connects INTx of each >> devices behind it to system board interrupt line and it is part of PCI >> spec (page 30 of PCI3.0 spec). Note that the function return pin, not >> interrupt line. To get interrupt line we look into pci_irqs[] array. > The swizzling of INTx-pins happens in PCI-to-PCI bridges. But it looks > like the pci_slot_get_pirq function is applied to all devices, including > those on the top-level bus that are not behind any PCI-to-PCI bridge. > Further, the function only looks at device (slot) and doesn't care where > the device is in the PCI hierarchy.
The pci_slot_get_pirq() appears to be taken directly from hw/piix_pci.c in the qemu source. So, it represents the "motherboard" mapping of irq lines on bus 0. Note, the mapping isn't the same as the swizzling of PCI-to-PCI bridges - on a pci bridge, INTA# of device 0 would map to the upstream INTA# pin, but the pci_slot_get_pirq() would actually map it to INTD#. The code is in line with the ACPI mapping in src/acpi-dsdt.dsl and the PIR mapping in src/pirtable.c. -Kevin
