xref: /haiku/src/system/kernel/arch/generic/acpi_irq_routing_table.cpp (revision cd806508a89edf7be95685df9f7c34bd03db7147)

/*
 * Copyright 2011, Michael Lotz mmlr@mlotz.ch.
 * Copyright 2009, Clemens Zeidler haiku@clemens-zeidler.de.
 * All rights reserved.
 *
 * Distributed under the terms of the MIT License.
 */


#include "acpi_irq_routing_table.h"

#include "acpi.h"

#include <int.h>

#include <PCI.h>


//#define TRACE_PRT
#ifdef TRACE_PRT
#	define TRACE(x...) dprintf("IRQRoutingTable: " x)
#else
#	define TRACE(x...)
#endif


const char* kACPIPciRootName = "PNP0A03";
const char* kACPIPciExpressRootName = "PNP0A08";
	// Note that some configurations will still return the PCI express root
	// when querying for the standard PCI root. This is due to the compatible ID
	// fields in ACPI. TODO: Query both/the correct root device.

// TODO: as per PCI 3.0, the PCI module hardcodes it in various places as well.
static const uint8 kMaxPCIFunctionCount = 8;
static const uint8 kMaxPCIDeviceCount = 32;
	// TODO: actually this is mechanism dependent
#if defined(__i386__) || defined(__x86_64__)
static const uint8 kMaxISAInterrupts = 16;
#else
static const uint8 kMaxISAInterrupts = 0;
#endif

irq_descriptor::irq_descriptor()
	:
	irq(0),
	shareable(false),
	polarity(B_HIGH_ACTIVE_POLARITY),
	trigger_mode(B_EDGE_TRIGGERED)
{
}


void
print_irq_descriptor(const irq_descriptor& descriptor)
{
	const char* activeHighString = "active high";
	const char* activeLowString = " active low";
	const char* levelTriggeredString = "level triggered";
	const char* edgeTriggeredString = "edge triggered";

	dprintf("irq: %u, shareable: %u, polarity: %s, trigger_mode: %s\n",
		descriptor.irq, descriptor.shareable,
		descriptor.polarity == B_HIGH_ACTIVE_POLARITY ? activeHighString
			: activeLowString,
		descriptor.trigger_mode == B_LEVEL_TRIGGERED ? levelTriggeredString
			: edgeTriggeredString);
}


static void
print_irq_routing_entry(const irq_routing_entry& entry)
{
	dprintf("address 0x%04" B_PRIx64 "; pin %u;", entry.device_address,
		entry.pin);

	if (entry.source_index != 0)
		dprintf(" GSI %" B_PRIu32 ";", entry.source_index);
	else
		dprintf(" source %p %" B_PRIu32 ";", entry.source, entry.source_index);

	dprintf(" pci %u:%u pin %u func mask %" B_PRIx32 "; bios irq: %u; gsi %u;"
		" config 0x%02x\n", entry.pci_bus, entry.pci_device, entry.pin + 1,
		entry.pci_function_mask, entry.bios_irq, entry.irq,
		entry.polarity | entry.trigger_mode);
}


void
print_irq_routing_table(const IRQRoutingTable& table)
{
	dprintf("IRQ routing table with %i entries\n", (int)table.Count());
	for (int i = 0; i < table.Count(); i++)
		print_irq_routing_entry(table.ElementAt(i));
}


static status_t
update_pci_info_for_entry(pci_module_info* pci, const irq_routing_entry& entry)
{
	uint32 updateCount = 0;
	for (uint8 function = 0; function < kMaxPCIFunctionCount; function++) {
		if ((entry.pci_function_mask & (1 << function)) == 0)
			continue;

		if (pci->update_interrupt_line(entry.pci_bus, entry.pci_device,
			function, entry.irq) == B_OK) {
			updateCount++;
		}
	}

	return updateCount > 0 ? B_OK : B_ENTRY_NOT_FOUND;
}


static status_t
fill_pci_info_for_entry(pci_module_info* pci, irq_routing_entry& entry)
{
	// check the base device at function 0
	uint8 headerType = pci->read_pci_config(entry.pci_bus, entry.pci_device, 0,
		PCI_header_type, 1);
	if (headerType == 0xff) {
		TRACE("PCI %" B_PRIu8 ":%" B_PRIu8 " entry not found\n",
			entry.pci_bus, entry.pci_device);
		// the device is not present
		return B_ENTRY_NOT_FOUND;
	}

	// we have a device, check how many functions we need to iterate
	uint8 functionCount = 1;
	if ((headerType & PCI_multifunction) != 0)
		functionCount = kMaxPCIFunctionCount;

	for (uint8 function = 0; function < functionCount; function++) {
		// check for device presence by looking for a valid vendor
		uint16 vendorId = pci->read_pci_config(entry.pci_bus, entry.pci_device,
			function, PCI_vendor_id, 2);
		if (vendorId == 0xffff) {
			TRACE("PCI %" B_PRIu8 ":%" B_PRIu8 ":%" B_PRIu8 " vendor 0xffff\n",
				entry.pci_bus, entry.pci_device, function);
			continue;
		}

		uint8 interruptPin = pci->read_pci_config(entry.pci_bus,
			entry.pci_device, function, PCI_interrupt_pin, 1);

		// Finally match the pin with the entry, note that PCI pins are 1 based
		// while ACPI ones are 0 based.
		if (interruptPin != entry.pin + 1) {
			TRACE("PCI %" B_PRIu8 ":%" B_PRIu8 ":%" B_PRIu8 " IRQ Pin %" B_PRIu8
				" != %" B_PRIu8 "\n", entry.pci_bus, entry.pci_device, function,
				interruptPin, entry.pin + 1);
			continue;
		}

		if (entry.bios_irq == 0) {
			// Keep the originally assigned IRQ around so we can use it for
			// white listing PCI IRQs in the ISA space as those are basically
			// guaranteed not to overlap with ISA devices. Those white listed
			// entries can then be used if we only have a 16 pin IO-APIC or if
			// there are only legacy IRQ resources available for configuration
			// (with bitmasks of 16 bits, limiting their range to ISA IRQs).
			entry.bios_irq = pci->read_pci_config(entry.pci_bus,
				entry.pci_device, function, PCI_interrupt_line, 1);
		}

		entry.pci_function_mask |= 1 << function;
	}

	return entry.pci_function_mask != 0 ? B_OK : B_ENTRY_NOT_FOUND;
}


static status_t
choose_link_device_configurations(acpi_module_info* acpi,
	IRQRoutingTable& routingTable,
	interrupt_available_check_function checkFunction)
{
	/*
		Before configuring the link devices we have to take a few things into
		consideration:
		* Multiple PCI devices / functions may link to the same PCI link
		  device, so we must ensure that we don't try to configure different
		  IRQs for each device, overwriting the previous config of the
		  respective link device.
		* If we can't use non-ISA IRQs then we must ensure that we don't
		  configure any IRQs that overlaps with ISA devices (as they use
		  different triggering modes and polarity they aren't compatible).
		  Since the ISA bus isn't enumerable we don't have any clues as to
		  where an ISA device might be connected. The only safe assumption
		  therefore is to only use IRQs that are known to be usable for PCI
		  devices. In our case we can use all the previously assigned PCI
		  interrupt_line IRQs as stored in the bios_irq field.
	*/

	uint16 validForPCI = 0; // only applies to the ISA IRQs
	uint16 irqUsage[256];
	memset(irqUsage, 0, sizeof(irqUsage));

	// find all unique link devices and resolve their possible IRQs
	Vector<link_device*> links;
	for (int i = 0; i < routingTable.Count(); i++) {
		irq_routing_entry& irqEntry = routingTable.ElementAt(i);

		if (irqEntry.bios_irq != 0 && irqEntry.bios_irq != 255) {
			if (irqEntry.bios_irq < kMaxISAInterrupts)
				validForPCI |= (1 << irqEntry.bios_irq);
		}

		if (irqEntry.source == NULL) {
			// populate all hardwired GSI entries into our map
			irqUsage[irqEntry.irq]++;
			if (irqEntry.irq < kMaxISAInterrupts)
				validForPCI |= (1 << irqEntry.irq);
			continue;
		}

		link_device* link = NULL;
		for (int j = 0; j < links.Count(); j++) {
			link_device* existing = links.ElementAt(j);
			if (existing->handle == irqEntry.source) {
				link = existing;
				break;
			}
		}

		if (link != NULL) {
			link->used_by.PushBack(&irqEntry);
			continue;
		}

		// A new link device, read possible IRQs and fill them in.
		link = new(std::nothrow) link_device;
		if (link == NULL) {
			panic("ran out of memory while configuring irq link devices");
			return B_NO_MEMORY;
		}

		link->handle = irqEntry.source;
		status_t status = read_possible_irqs(acpi, link->handle,
			link->possible_irqs);
		if (status != B_OK) {
			panic("failed to read possible irqs of link device");
			delete link;
			return status;
		}

		status = read_current_irq(acpi, link->handle, link->current_irq);
		if (status != B_OK) {
			panic("failed to read current irq of link device");
			delete link;
			return status;
		}

		if (link->current_irq.irq < kMaxISAInterrupts)
			validForPCI |= (1 << link->current_irq.irq);

		link->used_by.PushBack(&irqEntry);
		links.PushBack(link);
	}

	for (int i = 0; i < links.Count(); i++) {
		link_device* link = links.ElementAt(i);

		int bestIRQIndex = 0;
		uint16 bestIRQUsage = UINT16_MAX;
		for (int j = 0; j < link->possible_irqs.Count(); j++) {
			irq_descriptor& possibleIRQ = link->possible_irqs.ElementAt(j);
			if (!checkFunction(possibleIRQ.irq)) {
				// we can't address this pin
				continue;
			}

			if (possibleIRQ.irq < kMaxISAInterrupts
				&& (validForPCI & (1 << possibleIRQ.irq)) == 0) {
				// better avoid that if possible
				continue;
			}

			if (irqUsage[possibleIRQ.irq] < bestIRQUsage) {
				bestIRQIndex = j;
				bestIRQUsage = irqUsage[possibleIRQ.irq];
			}
		}

		// pick that one and update the counts
		irq_descriptor& chosenDescriptor
			= link->possible_irqs.ElementAt(bestIRQIndex);
		if (!checkFunction(chosenDescriptor.irq)) {
			dprintf("chosen irq %u is not addressable\n", chosenDescriptor.irq);
			return B_ERROR;
		}

		irqUsage[chosenDescriptor.irq] += link->used_by.Count();

		for (int j = 0; j < link->used_by.Count(); j++) {
			irq_routing_entry* irqEntry = link->used_by.ElementAt(j);
			irqEntry->needs_configuration = j == 0; // only configure once
			irqEntry->irq = chosenDescriptor.irq;
			irqEntry->polarity = chosenDescriptor.polarity;
			irqEntry->trigger_mode = chosenDescriptor.trigger_mode;
		}

		delete link;
	}

	return B_OK;
}


static status_t
configure_link_devices(acpi_module_info* acpi, IRQRoutingTable& routingTable)
{
	for (int i = 0; i < routingTable.Count(); i++) {
		irq_routing_entry& irqEntry = routingTable.ElementAt(i);
		if (!irqEntry.needs_configuration)
			continue;

		irq_descriptor configuration;
		configuration.irq = irqEntry.irq;
		configuration.polarity = irqEntry.polarity;
		configuration.trigger_mode = irqEntry.trigger_mode;

		status_t status = set_current_irq(acpi, irqEntry.source, configuration);
		if (status != B_OK) {
			dprintf("failed to set irq on link device, keeping current\n");
			print_irq_descriptor(configuration);

			// we failed to set the resource, fall back to current
			read_current_irq(acpi, irqEntry.source, configuration);
			for (int j = i; j < routingTable.Count(); j++) {
				irq_routing_entry& other = routingTable.ElementAt(j);
				if (other.source == irqEntry.source) {
					other.irq = configuration.irq;
					other.polarity = configuration.polarity;
					other.trigger_mode = configuration.trigger_mode;
				}
			}
		}

		irqEntry.needs_configuration = false;
	}

	return B_OK;
}


static status_t
evaluate_integer(acpi_module_info* acpi, acpi_handle handle,
	const char* method, uint64& value)
{
	acpi_object_type result;
	acpi_data resultBuffer;
	resultBuffer.pointer = &result;
	resultBuffer.length = sizeof(result);

	status_t status = acpi->evaluate_method(handle, method, NULL,
		&resultBuffer);
	if (status != B_OK)
		return status;

	if (result.object_type != ACPI_TYPE_INTEGER)
		return B_BAD_TYPE;

	value = result.integer.integer;
	return B_OK;
}


static status_t
handle_routing_table_entry(acpi_module_info* acpi, pci_module_info* pci,
	acpi_handle parent, const acpi_pci_routing_table* acpiTable,
	uint8 currentBus, irq_routing_entry& irqEntry)
{
	bool noSource = acpiTable->Source[0] == '\0';
		// The above line would be correct according to specs...
	noSource = acpiTable->SourceIndex != 0;
		// ... but we use this one as there seem to be quirks where
		// a source is indicated but not actually present. With a source
		// index != 0 a GSI is generally indicated.

	status_t status;
	acpi_handle source;
	if (!noSource) {
		status = acpi->get_handle(parent, acpiTable->Source, &source);
		if (status != B_OK) {
			dprintf("failed to get handle to link device\n");
			return status;
		}
	}

	memset(&irqEntry, 0, sizeof(irq_routing_entry));
	irqEntry.device_address = acpiTable->Address;
	irqEntry.pin = acpiTable->Pin;
	irqEntry.source = noSource ? NULL : source;
	irqEntry.source_index = acpiTable->SourceIndex;
	irqEntry.pci_bus = currentBus;
	irqEntry.pci_device = (uint8)(acpiTable->Address >> 16);

	status = fill_pci_info_for_entry(pci, irqEntry);
	if (status != B_OK) {
		// Note: This isn't necesarily fatal, as there can be many entries in
		// the table pointing to disabled/optional devices. Also they can be
		// used to describe the full actual wireing regardless of the presence
		// of devices, in which case many entries won't have a match.
#ifdef TRACE_PRT
		dprintf("no matching PCI device for irq entry: ");
		print_irq_routing_entry(irqEntry);
#endif
	} else {
#ifdef TRACE_PRT
		dprintf("found matching PCI device for irq entry: ");
		print_irq_routing_entry(irqEntry);
#endif
	}

	if (noSource) {
		// fill in the GSI and config
		irqEntry.needs_configuration = false;
		irqEntry.irq = irqEntry.source_index;
		irqEntry.polarity = B_LOW_ACTIVE_POLARITY;
		irqEntry.trigger_mode = B_LEVEL_TRIGGERED;
	}

	return B_OK;
}


irq_routing_entry*
find_routing_table_entry(IRQRoutingTable& table, uint8 bus, uint8 device,
	uint8 pin)
{
	for (int i = 0; i < table.Count(); i++) {
		irq_routing_entry& irqEntry = table.ElementAt(i);
		if (irqEntry.pci_bus != bus || irqEntry.pci_device != device)
			continue;

		if (irqEntry.pin + 1 == pin)
			return &irqEntry;
	}

	return NULL;
}


static status_t
ensure_all_functions_matched(pci_module_info* pci, uint8 bus,
	IRQRoutingTable& matchedTable, IRQRoutingTable& unmatchedTable,
	Vector<pci_address>& parents)
{
	for (uint8 device = 0; device < kMaxPCIDeviceCount; device++) {
		if (pci->read_pci_config(bus, device, 0, PCI_vendor_id, 2) == 0xffff) {
			TRACE("PCI bus %" B_PRIu8 ":%" B_PRIu8 " not present.\n",
				bus, device);
			// not present
			continue;
		}

		uint8 headerType = pci->read_pci_config(bus, device, 0,
			PCI_header_type, 1);

		uint8 functionCount = 1;
		if ((headerType & PCI_multifunction) != 0)
			functionCount = kMaxPCIFunctionCount;

		for (uint8 function = 0; function < functionCount; function++) {
			// check for device presence by looking for a valid vendor
			if (pci->read_pci_config(bus, device, function, PCI_vendor_id, 2)
				== 0xffff) {
				// not present
				TRACE("PCI %" B_PRIu8 ":%" B_PRIu8 ":%" B_PRIu8 " "
					"not present.\n", bus, device, function);
				continue;
			}

			if (function > 0) {
				headerType = pci->read_pci_config(bus, device, function,
					PCI_header_type, 1);
			}

			// if this is a bridge, recurse down
			if ((headerType & PCI_header_type_mask)
				== PCI_header_type_PCI_to_PCI_bridge) {

				pci_address pciAddress;
				pciAddress.segment = 0;
				pciAddress.bus = bus;
				pciAddress.device = device;
				pciAddress.function = function;

				parents.PushBack(pciAddress);

				uint8 secondaryBus = pci->read_pci_config(bus, device, function,
					PCI_secondary_bus, 1);
				if (secondaryBus != 0xff) {
					ensure_all_functions_matched(pci, secondaryBus,
						matchedTable, unmatchedTable, parents);
				}

				parents.PopBack();
			}

			uint8 interruptPin = pci->read_pci_config(bus, device, function,
				PCI_interrupt_pin, 1);
			if (interruptPin == 0 || interruptPin > 4) {
				TRACE("PCI %" B_PRIu8 ":%" B_PRIu8 ":%" B_PRIu8 " "
					"not routed.\n", bus, device, function);
				// not routed
				continue;
			}

			irq_routing_entry* irqEntry = find_routing_table_entry(matchedTable,
				bus, device, interruptPin);
			if (irqEntry != NULL) {
				// we already have a matching entry for that device/pin, make
				// sure the function mask includes us
				TRACE("PCI %" B_PRIu8 ":%" B_PRIu8 ":%" B_PRIu8 " "
					"already matched. Will mask.\n", bus, device, function);
				irqEntry->pci_function_mask |= 1 << function;
				continue;
			}

			TRACE("PCI %" B_PRIu8 ":%" B_PRIu8 ":%" B_PRIu8 " has %" B_PRIu8 " "
				"parents, searching them...\n", bus, device, function,
				parents.Count());

			// This function has no matching routing table entry yet. Try to
			// figure one out in the parent, based on the device number and
			// interrupt pin.
			bool matched = false;
			uint8 parentPin = ((device + interruptPin - 1) % 4) + 1;
			for (int i = parents.Count() - 1; i >= 0; i--) {
				pci_address& parent = parents.ElementAt(i);
				irqEntry = find_routing_table_entry(matchedTable, parent.bus,
					parent.device, parentPin);
				if (irqEntry == NULL) {
					// try the unmatched table as well
					TRACE("PCI %" B_PRIu8 ":%" B_PRIu8 ":%" B_PRIu8 " "
						"no matchedTable entry.\n", bus, device, function);
					irqEntry = find_routing_table_entry(unmatchedTable,
						parent.bus, parent.device, parentPin);
				}

				if (irqEntry == NULL) {
					// no match in that parent, go further up
					parentPin = ((parent.device + parentPin - 1) % 4) + 1;

					TRACE("PCI %" B_PRIu8 ":%" B_PRIu8 ":%" B_PRIu8 " "
						"no unmatchedTable entry, looking at parent pin %"
						B_PRIu8 "...\n", bus, device, function, parentPin);
					continue;
				}

				// found a match, make a copy and add it to the table
				irq_routing_entry newEntry = *irqEntry;
				newEntry.device_address = (device << 16) | 0xffff;
				newEntry.pin = interruptPin - 1;
				newEntry.pci_bus = bus;
				newEntry.pci_device = device;
				newEntry.pci_function_mask = 1 << function;

				uint8 biosIRQ = pci->read_pci_config(bus, device, function,
					PCI_interrupt_line, 1);
				if (biosIRQ != 0 && biosIRQ != 255) {
					if (newEntry.bios_irq != 0 && newEntry.bios_irq != 255
						&& newEntry.bios_irq != biosIRQ) {
						// If the function was actually routed to that pin,
						// the two bios irqs should match. If they don't
						// that means we're not correct in our routing
						// assumption.
						panic("calculated irq routing doesn't match bios for "
							"PCI %u:%u:%u", bus, device, function);
						return B_ERROR;
					}

					newEntry.bios_irq = biosIRQ;
				}

				dprintf("calculated irq routing entry: ");
				print_irq_routing_entry(newEntry);

				matchedTable.PushBack(newEntry);
				matched = true;
				break;
			}

			if (!matched) {
				uint32 interrupt_line = pci->read_pci_config(bus, device,
					function, PCI_interrupt_line, 1);
				// On x86, interrupt line 255 means "unknown" or "no connection"
				// (PCI Local Bus spec 3.0, section 6.2.4 / page 223, footnote.)
				if (interrupt_line == 0 || interrupt_line == 255) {
					dprintf("assuming no interrupt use on PCI device"
						" %u:%u:%u (bios irq 0, interrupt line %" B_PRId32 ")\n",
						bus, device, function, interrupt_line);
					continue;
				}

				dprintf("WARNING: unable to find irq routing for PCI "
					"%" B_PRIu8 ":%" B_PRIu8 ":%" B_PRIu8 ". Device may be "
					"unstable / broken.\n", bus, device, function);
				return B_ERROR;
			}
		}
	}

	return B_OK;
}


static status_t
read_irq_routing_table_recursive(acpi_module_info* acpi, pci_module_info* pci,
	acpi_handle parent, acpi_handle device, uint8 currentBus,
	IRQRoutingTable& table, IRQRoutingTable& unmatchedTable, bool rootBridge,
	interrupt_available_check_function checkFunction)
{
	if (!rootBridge) {
		// check if this actually is a bridge
		uint64 value;
		pci_address pciAddress;
		pciAddress.bus = currentBus;
		if (evaluate_integer(acpi, device, "_ADR", value) == B_OK) {
			pciAddress.device = (uint8)(value >> 16);
			pciAddress.function = (uint8)value;
		} else {
			pciAddress.device = 0;
			pciAddress.function = 0;
		}

		if (pciAddress.device >= kMaxPCIDeviceCount
			|| pciAddress.function >= kMaxPCIFunctionCount) {
			// we don't seem to be on the PCI bus anymore
			// (just a different type of device)
			return B_OK;
		}

		// Verify that the device is really present...
		uint16 deviceID = pci->read_pci_config(pciAddress.bus,
			pciAddress.device, pciAddress.function, PCI_device_id, 2);
		if (deviceID == 0xffff) {
			// Not present or disabled.
			TRACE("device not present\n");
			return B_OK;
		}

		// ... and that it really is a PCI bridge we support.
		uint8 baseClass = pci->read_pci_config(pciAddress.bus,
			pciAddress.device, pciAddress.function, PCI_class_base, 1);
		uint8 subClass = pci->read_pci_config(pciAddress.bus,
			pciAddress.device, pciAddress.function, PCI_class_sub, 1);
		if (baseClass != PCI_bridge || subClass != PCI_pci) {
			// Not a bridge or an unsupported one.
			TRACE("not a PCI bridge\n");
			return B_OK;
		}

		uint8 headerType = pci->read_pci_config(pciAddress.bus,
			pciAddress.device, pciAddress.function, PCI_header_type, 1);

		switch (headerType & PCI_header_type_mask) {
			case PCI_header_type_PCI_to_PCI_bridge:
			case PCI_header_type_cardbus:
				TRACE("found a PCI bridge (0x%02x)\n", headerType);
				break;

			default:
				// Unsupported header type.
				TRACE("unsupported header type (0x%02x)\n", headerType);
				return B_OK;
		}

		// Find the secondary bus number (the "downstream" bus number for the
		// attached devices) in the bridge configuration.
		uint8 secondaryBus = pci->read_pci_config(pciAddress.bus,
			pciAddress.device, pciAddress.function, PCI_secondary_bus, 1);
		if (secondaryBus == 255) {
			// The bus below this bridge is inactive, nothing to do.
			TRACE("secondary bus is inactive\n");
			return B_OK;
		}

		// The secondary bus cannot be the same as the current one.
		if (secondaryBus == currentBus) {
			dprintf("invalid secondary bus %u on primary bus %u,"
				" can't configure irq routing of devices below\n",
				secondaryBus, currentBus);
			// TODO: Maybe we want to just return B_OK anyway so that we don't
			// fail this step. We ensure that we matched all devices at the
			// end of preparation, so we'd detect missing child devices anyway
			// and it would not cause us to fail for empty misconfigured busses
			// that we don't actually care about.
			return B_ERROR;
		}

		// Everything below is now on the secondary bus.
		TRACE("now scanning bus %u\n", secondaryBus);
		currentBus = secondaryBus;
	}

	acpi_data buffer;
	buffer.pointer = NULL;
	buffer.length = ACPI_ALLOCATE_BUFFER;
	status_t status = acpi->get_irq_routing_table(device, &buffer);
	if (status == B_OK) {
		TRACE("found irq routing table\n");

		acpi_pci_routing_table* acpiTable
			= (acpi_pci_routing_table*)buffer.pointer;
		while (acpiTable->Length) {
			irq_routing_entry irqEntry;
			status = handle_routing_table_entry(acpi, pci, parent, acpiTable,
				currentBus, irqEntry);
			if (status == B_OK) {
				if (irqEntry.source == NULL && !checkFunction(irqEntry.irq)) {
					dprintf("hardwired irq %u not addressable\n", irqEntry.irq);
					free(buffer.pointer);
					return B_ERROR;
				}

				if (irqEntry.pci_function_mask != 0)
					table.PushBack(irqEntry);
				else
					unmatchedTable.PushBack(irqEntry);
			}

			acpiTable = (acpi_pci_routing_table*)((uint8*)acpiTable
				+ acpiTable->Length);
		}

		free(buffer.pointer);
	} else {
		TRACE("no irq routing table present\n");
	}

	// recurse down the ACPI child devices
	acpi_data pathBuffer;
	pathBuffer.pointer = NULL;
	pathBuffer.length = ACPI_ALLOCATE_BUFFER;
	status = acpi->ns_handle_to_pathname(device, &pathBuffer);
	if (status != B_OK) {
		dprintf("failed to resolve handle to path\n");
		return status;
	}

	char childName[255];
	void* counter = NULL;
	while (acpi->get_next_entry(ACPI_TYPE_DEVICE, (char*)pathBuffer.pointer,
		childName, sizeof(childName), &counter) == B_OK) {

		acpi_handle childHandle;
		status = acpi->get_handle(NULL, childName, &childHandle);
		if (status != B_OK) {
			dprintf("failed to get handle to child \"%s\"\n", childName);
			break;
		}

		TRACE("recursing down to child \"%s\"\n", childName);
		status = read_irq_routing_table_recursive(acpi, pci, device, childHandle,
			currentBus, table, unmatchedTable, false, checkFunction);
		if (status != B_OK)
			break;
	}

	free(pathBuffer.pointer);
	return status;
}


static status_t
read_irq_routing_table(acpi_module_info* acpi, IRQRoutingTable& table,
	interrupt_available_check_function checkFunction)
{
	char rootPciName[255];
	acpi_handle rootPciHandle;
	rootPciName[0] = 0;
	status_t status = acpi->get_device(kACPIPciRootName, 0, rootPciName, 255);
	if (status != B_OK)
		return status;

	status = acpi->get_handle(NULL, rootPciName, &rootPciHandle);
	if (status != B_OK)
		return status;

	// We reset the root bus to 0 here. Any failed evaluation means default
	// values, so we don't have to do anything in the error case.
	uint8 rootBus = 0;

	uint64 value;
	if (evaluate_integer(acpi, rootPciHandle, "_BBN", value) == B_OK)
		rootBus = (uint8)value;

#if 0
	// TODO: handle
	if (evaluate_integer(acpi, rootPciHandle, "_SEG", value) == B_OK)
		rootPciAddress.segment = (uint8)value;
#endif

	pci_module_info* pci;
	status = get_module(B_PCI_MODULE_NAME, (module_info**)&pci);
	if (status != B_OK) {
		// shouldn't happen, since the PCI module is a dependency of the
		// ACPI module and we shouldn't be here at all if it wasn't loaded
		dprintf("failed to get PCI module!\n");
		return status;
	}

	IRQRoutingTable unmatchedTable;
	status = read_irq_routing_table_recursive(acpi, pci, ACPI_ROOT_OBJECT,
		rootPciHandle, rootBus, table, unmatchedTable, true, checkFunction);
	if (status != B_OK) {
		put_module(B_PCI_MODULE_NAME);
		return status;
	}

	if (table.Count() == 0) {
		put_module(B_PCI_MODULE_NAME);
		return B_ERROR;
	}

	// Now go through all the PCI devices and verify that they have a routing
	// table entry. For the devices without a match, we calculate their pins
	// on the bridges and try to match these in the parent routing table. We
	// do this recursively going up the tree until we find a match or arrive
	// at the top.
	Vector<pci_address> parents;
	status = ensure_all_functions_matched(pci, rootBus, table, unmatchedTable,
		parents);

	put_module(B_PCI_MODULE_NAME);
	return status;
}


status_t
prepare_irq_routing(acpi_module_info* acpi, IRQRoutingTable& routingTable,
	interrupt_available_check_function checkFunction)
{
	status_t status = read_irq_routing_table(acpi, routingTable, checkFunction);
	if (status != B_OK)
		return status;

	// resolve desired configuration of link devices
	return choose_link_device_configurations(acpi, routingTable, checkFunction);
}


status_t
enable_irq_routing(acpi_module_info* acpi, IRQRoutingTable& routingTable)
{
	// configure the link devices; also resolves GSIs for link based entries
	status_t status = configure_link_devices(acpi, routingTable);
	if (status != B_OK) {
		panic("failed to configure link devices");
		return status;
	}

	pci_module_info* pci;
	status = get_module(B_PCI_MODULE_NAME, (module_info**)&pci);
	if (status != B_OK) {
		// shouldn't happen, since the PCI module is a dependency of the
		// ACPI module and we shouldn't be here at all if it wasn't loaded
		dprintf("failed to get PCI module!\n");
		return status;
	}

	// update the PCI info now that all GSIs are known
	for (int i = 0; i < routingTable.Count(); i++) {
		irq_routing_entry& irqEntry = routingTable.ElementAt(i);

		status = update_pci_info_for_entry(pci, irqEntry);
		if (status != B_OK) {
			dprintf("failed to update interrupt_line for PCI %u:%u mask %"
				B_PRIx32 "\n", irqEntry.pci_bus, irqEntry.pci_device,
				irqEntry.pci_function_mask);
		}
	}

	put_module(B_PCI_MODULE_NAME);
	return B_OK;
}


static status_t
read_irq_descriptor(acpi_module_info* acpi, acpi_handle device,
	bool readCurrent, irq_descriptor* _descriptor,
	irq_descriptor_list* descriptorList)
{
	acpi_data buffer;
	buffer.pointer = NULL;
	buffer.length = ACPI_ALLOCATE_BUFFER;

	status_t status;
	if (readCurrent)
		status = acpi->get_current_resources(device, &buffer);
	else
		status = acpi->get_possible_resources(device, &buffer);

	if (status != B_OK) {
		dprintf("failed to read %s resources for irq\n",
			readCurrent ? "current" : "possible");
		free(buffer.pointer);
		return status;
	}

	irq_descriptor descriptor;
	descriptor.irq = 255;

	acpi_resource* resource = (acpi_resource*)buffer.pointer;
	while (resource->Type != ACPI_RESOURCE_TYPE_END_TAG) {
		switch (resource->Type) {
			case ACPI_RESOURCE_TYPE_IRQ:
			{
				acpi_resource_irq& irq = resource->Data.Irq;
				if (irq.InterruptCount < 1) {
					dprintf("acpi irq resource with no interrupts\n");
					break;
				}

				descriptor.shareable = irq.Shareable != 0;
				descriptor.trigger_mode = irq.Triggering == 0
					? B_LEVEL_TRIGGERED : B_EDGE_TRIGGERED;
				descriptor.polarity = irq.Polarity == 0
					? B_HIGH_ACTIVE_POLARITY : B_LOW_ACTIVE_POLARITY;

				if (readCurrent)
					descriptor.irq = irq.Interrupts[0];
				else {
					for (uint16 i = 0; i < irq.InterruptCount; i++) {
						descriptor.irq = irq.Interrupts[i];
						descriptorList->PushBack(descriptor);
					}
				}

#ifdef TRACE_PRT
				dprintf("acpi irq resource (%s):\n",
					readCurrent ? "current" : "possible");
				dprintf("\ttriggering: %s\n",
					irq.Triggering == 0 ? "level" : "edge");
				dprintf("\tpolarity: %s active\n",
					irq.Polarity == 0 ? "high" : "low");
				dprintf("\tshareable: %s\n", irq.Shareable != 0 ? "yes" : "no");
				dprintf("\tcount: %u\n", irq.InterruptCount);
				if (irq.InterruptCount > 0) {
					dprintf("\tinterrupts:");
					for (uint16 i = 0; i < irq.InterruptCount; i++)
						dprintf(" %u", irq.Interrupts[i]);
					dprintf("\n");
				}
#endif
				break;
			}

			case ACPI_RESOURCE_TYPE_EXTENDED_IRQ:
			{
				acpi_resource_extended_irq& irq = resource->Data.ExtendedIrq;
				if (irq.InterruptCount < 1) {
					dprintf("acpi extended irq resource with no interrupts\n");
					break;
				}

				descriptor.shareable = irq.Shareable != 0;
				descriptor.trigger_mode = irq.Triggering == 0
					? B_LEVEL_TRIGGERED : B_EDGE_TRIGGERED;
				descriptor.polarity = irq.Polarity == 0
					? B_HIGH_ACTIVE_POLARITY : B_LOW_ACTIVE_POLARITY;

				if (readCurrent)
					descriptor.irq = irq.Interrupts[0];
				else {
					for (uint16 i = 0; i < irq.InterruptCount; i++) {
						descriptor.irq = irq.Interrupts[i];
						descriptorList->PushBack(descriptor);
					}
				}

#ifdef TRACE_PRT
				dprintf("acpi extended irq resource (%s):\n",
					readCurrent ? "current" : "possible");
				dprintf("\tproducer: %s\n",
					irq.ProducerConsumer ? "yes" : "no");
				dprintf("\ttriggering: %s\n",
					irq.Triggering == 0 ? "level" : "edge");
				dprintf("\tpolarity: %s active\n",
					irq.Polarity == 0 ? "high" : "low");
				dprintf("\tshareable: %s\n", irq.Shareable != 0 ? "yes" : "no");
				dprintf("\tcount: %u\n", irq.InterruptCount);
				if (irq.InterruptCount > 0) {
					dprintf("\tinterrupts:");
					for (uint16 i = 0; i < irq.InterruptCount; i++)
						dprintf(" %u", irq.Interrupts[i]);
					dprintf("\n");
				}
#endif
				break;
			}
		}

		if (descriptor.irq != 255)
			break;

		resource = (acpi_resource*)((uint8*)resource + resource->Length);
	}

	free(buffer.pointer);

	if (descriptor.irq == 255)
		return B_ERROR;

	if (readCurrent)
		*_descriptor = descriptor;

	return B_OK;
}


status_t
read_current_irq(acpi_module_info* acpi, acpi_handle device,
	irq_descriptor& descriptor)
{
	return read_irq_descriptor(acpi, device, true, &descriptor, NULL);
}


status_t
read_possible_irqs(acpi_module_info* acpi, acpi_handle device,
	irq_descriptor_list& descriptorList)
{
	return read_irq_descriptor(acpi, device, false, NULL, &descriptorList);
}


status_t
set_current_irq(acpi_module_info* acpi, acpi_handle device,
	const irq_descriptor& descriptor)
{
	acpi_data buffer;
	buffer.pointer = NULL;
	buffer.length = ACPI_ALLOCATE_BUFFER;

	status_t status = acpi->get_current_resources(device, &buffer);
	if (status != B_OK) {
		dprintf("failed to read current resources for irq\n");
		return status;
	}

	bool irqWritten = false;
	acpi_resource* resource = (acpi_resource*)buffer.pointer;
	while (resource->Type != ACPI_RESOURCE_TYPE_END_TAG) {
		switch (resource->Type) {
			case ACPI_RESOURCE_TYPE_IRQ:
			{
				acpi_resource_irq& irq = resource->Data.Irq;
				if (irq.InterruptCount < 1) {
					dprintf("acpi irq resource with no interrupts\n");
					break;
				}

				irq.Triggering
					= descriptor.trigger_mode == B_LEVEL_TRIGGERED ? 0 : 1;
				irq.Polarity
					= descriptor.polarity == B_HIGH_ACTIVE_POLARITY ? 0 : 1;
				irq.Shareable = descriptor.shareable ? 0 : 1;
				irq.InterruptCount = 1;
				irq.Interrupts[0] = descriptor.irq;

				irqWritten = true;
				break;
			}

			case ACPI_RESOURCE_TYPE_EXTENDED_IRQ:
			{
				acpi_resource_extended_irq& irq = resource->Data.ExtendedIrq;
				if (irq.InterruptCount < 1) {
					dprintf("acpi extended irq resource with no interrupts\n");
					break;
				}

				irq.Triggering
					= descriptor.trigger_mode == B_LEVEL_TRIGGERED ? 0 : 1;
				irq.Polarity
					= descriptor.polarity == B_HIGH_ACTIVE_POLARITY ? 0 : 1;
				irq.Shareable = descriptor.shareable ? 0 : 1;
				irq.InterruptCount = 1;
				irq.Interrupts[0] = descriptor.irq;

				irqWritten = true;
				break;
			}
		}

		if (irqWritten)
			break;

		resource = (acpi_resource*)((uint8*)resource + resource->Length);
	}

	if (irqWritten) {
		status = acpi->set_current_resources(device, &buffer);
		if (status != B_OK)
			dprintf("failed to set irq resources\n");
	} else {
		dprintf("failed to write requested irq into resources\n");
		status = B_ERROR;
	}

	free(buffer.pointer);
	return status;
}