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// SPDX-License-Identifier: GPL-2.0
/*
* Support routines for initializing a PCI subsystem
*
* Extruded from code written by
* Dave Rusling (david.rusling@reo.mts.dec.com)
* David Mosberger (davidm@cs.arizona.edu)
* David Miller (davem@redhat.com)
*/
#include <linux/kernel.h>
#include <linux/pci.h>
#include <linux/errno.h>
#include <linux/ioport.h>
#include <linux/cache.h>
#include "pci.h"
void pci_assign_irq(struct pci_dev *dev)
{
u8 pin;
u8 slot = -1;
int irq = 0;
struct pci_host_bridge *hbrg = pci_find_host_bridge(dev->bus);
if (!(hbrg->map_irq)) {
pci_dbg(dev, "runtime IRQ mapping not provided by arch\n");
return;
}
/*
* If this device is not on the primary bus, we need to figure out
* which interrupt pin it will come in on. We know which slot it
* will come in on because that slot is where the bridge is. Each
* time the interrupt line passes through a PCI-PCI bridge we must
* apply the swizzle function.
*/
pci_read_config_byte(dev, PCI_INTERRUPT_PIN, &pin);
/* Cope with illegal. */
if (pin > 4)
pin = 1;
if (pin) {
/* Follow the chain of bridges, swizzling as we go. */
if (hbrg->swizzle_irq)
slot = (*(hbrg->swizzle_irq))(dev, &pin);
/*
* If a swizzling function is not used, map_irq() must
* ignore slot.
*/
irq = (*(hbrg->map_irq))(dev, slot, pin);
if (irq == -1)
irq = 0;
}
dev->irq = irq;
pci_dbg(dev, "assign IRQ: got %d\n", dev->irq);
/*
* Always tell the device, so the driver knows what is the real IRQ
* to use; the device does not use it.
*/
pci_write_config_byte(dev, PCI_INTERRUPT_LINE, irq);
}
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