The PCI legacy interrupts can be described with link devices, cf ACPI 6.4, s6.2.13 "_PRT (PCI Routing Table)". Link devices can have optional _SRS/_PRS methods to set the interrupt. In PCI Firmware Specification Revision 3.3, s4.3.2.1. "Resource Setting": """ A non-configurable device only specifies _CRS. However, if they are configurable, devices include _PRS to indicate the possible resource setting and _SRS to allow OSPM to specify a new resource allocation for the device. """ However, _PRS/_SRS methods are checked in drivers/acpi/pci_link.c, and the driver aborts if they are absent. E.g.: When _PRS is missing: ACPI: \_SB_.PCI0.LNKA: _CRS 36 not found in _PRS ACPI: \_SB_.PCI0.LNKA: No IRQ available. Try pci=noacpi or acpi=off
For reference, the initial check that the interrupt advertised in _CRS is also in _PRS should come from: https://bugzilla.kernel.org/show_bug.cgi?id=2665 https://bugzilla.kernel.org/show_bug.cgi?id=2733