static int pcibios_lookup_irq()

in pci/irq.c [1148:1297]

• 122 lines of code
• 43 McCabe index (conditional complexity)

static int pcibios_lookup_irq(struct pci_dev *dev, int assign)
{
	u8 pin;
	struct irq_info *info;
	int i, pirq, newirq;
	int irq = 0;
	u32 mask;
	struct irq_router *r = &pirq_router;
	struct pci_dev *dev2 = NULL;
	char *msg = NULL;

	/* Find IRQ pin */
	pci_read_config_byte(dev, PCI_INTERRUPT_PIN, &pin);
	if (!pin) {
		dev_dbg(&dev->dev, "no interrupt pin\n");
		return 0;
	}

	if (io_apic_assign_pci_irqs)
		return 0;

	/* Find IRQ routing entry */

	if (!pirq_table)
		return 0;

	info = pirq_get_info(dev);
	if (!info) {
		dev_dbg(&dev->dev, "PCI INT %c not found in routing table\n",
			'A' + pin - 1);
		return 0;
	}
	pirq = info->irq[pin - 1].link;
	mask = info->irq[pin - 1].bitmap;
	if (!pirq) {
		dev_dbg(&dev->dev, "PCI INT %c not routed\n", 'A' + pin - 1);
		return 0;
	}
	dev_dbg(&dev->dev, "PCI INT %c -> PIRQ %02x, mask %04x, excl %04x",
		'A' + pin - 1, pirq, mask, pirq_table->exclusive_irqs);
	mask &= pcibios_irq_mask;

	/* Work around broken HP Pavilion Notebooks which assign USB to
	   IRQ 9 even though it is actually wired to IRQ 11 */

	if (broken_hp_bios_irq9 && pirq == 0x59 && dev->irq == 9) {
		dev->irq = 11;
		pci_write_config_byte(dev, PCI_INTERRUPT_LINE, 11);
		r->set(pirq_router_dev, dev, pirq, 11);
	}

	/* same for Acer Travelmate 360, but with CB and irq 11 -> 10 */
	if (acer_tm360_irqrouting && dev->irq == 11 &&
		dev->vendor == PCI_VENDOR_ID_O2) {
		pirq = 0x68;
		mask = 0x400;
		dev->irq = r->get(pirq_router_dev, dev, pirq);
		pci_write_config_byte(dev, PCI_INTERRUPT_LINE, dev->irq);
	}

	/*
	 * Find the best IRQ to assign: use the one
	 * reported by the device if possible.
	 */
	newirq = dev->irq;
	if (newirq && !((1 << newirq) & mask)) {
		if (pci_probe & PCI_USE_PIRQ_MASK)
			newirq = 0;
		else
			dev_warn(&dev->dev, "IRQ %d doesn't match PIRQ mask "
				 "%#x; try pci=usepirqmask\n", newirq, mask);
	}
	if (!newirq && assign) {
		for (i = 0; i < 16; i++) {
			if (!(mask & (1 << i)))
				continue;
			if (pirq_penalty[i] < pirq_penalty[newirq] &&
				can_request_irq(i, IRQF_SHARED))
				newirq = i;
		}
	}
	dev_dbg(&dev->dev, "PCI INT %c -> newirq %d", 'A' + pin - 1, newirq);

	/* Check if it is hardcoded */
	if ((pirq & 0xf0) == 0xf0) {
		irq = pirq & 0xf;
		msg = "hardcoded";
	} else if (r->get && (irq = r->get(pirq_router_dev, dev, pirq)) && \
	((!(pci_probe & PCI_USE_PIRQ_MASK)) || ((1 << irq) & mask))) {
		msg = "found";
		if (r->lvl)
			r->lvl(pirq_router_dev, dev, pirq, irq);
		else
			elcr_set_level_irq(irq);
	} else if (newirq && r->set &&
		(dev->class >> 8) != PCI_CLASS_DISPLAY_VGA) {
		if (r->set(pirq_router_dev, dev, pirq, newirq)) {
			if (r->lvl)
				r->lvl(pirq_router_dev, dev, pirq, newirq);
			else
				elcr_set_level_irq(newirq);
			msg = "assigned";
			irq = newirq;
		}
	}

	if (!irq) {
		if (newirq && mask == (1 << newirq)) {
			msg = "guessed";
			irq = newirq;
		} else {
			dev_dbg(&dev->dev, "can't route interrupt\n");
			return 0;
		}
	}
	dev_info(&dev->dev, "%s PCI INT %c -> IRQ %d\n", msg, 'A' + pin - 1, irq);

	/* Update IRQ for all devices with the same pirq value */
	for_each_pci_dev(dev2) {
		pci_read_config_byte(dev2, PCI_INTERRUPT_PIN, &pin);
		if (!pin)
			continue;

		info = pirq_get_info(dev2);
		if (!info)
			continue;
		if (info->irq[pin - 1].link == pirq) {
			/*
			 * We refuse to override the dev->irq
			 * information. Give a warning!
			 */
			if (dev2->irq && dev2->irq != irq && \
			(!(pci_probe & PCI_USE_PIRQ_MASK) || \
			((1 << dev2->irq) & mask))) {
#ifndef CONFIG_PCI_MSI
				dev_info(&dev2->dev, "IRQ routing conflict: "
					 "have IRQ %d, want IRQ %d\n",
					 dev2->irq, irq);
#endif
				continue;
			}
			dev2->irq = irq;
			pirq_penalty[irq]++;
			if (dev != dev2)
				dev_info(&dev->dev, "sharing IRQ %d with %s\n",
					 irq, pci_name(dev2));
		}
	}
	return 1;
}