legacy.c

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/*
 * legacy.c - traditional, old school PCI bus probing
 */
#include <linux/init.h>
#include <linux/export.h>
#include <linux/pci.h>
#include <asm/pci_x86.h>

/*
 * Discover remaining PCI buses in case there are peer host bridges.
 * We use the number of last PCI bus provided by the PCI BIOS.
 */
static void __devinit pcibios_fixup_peer_bridges(void)
{
    int n;

    if (pcibios_last_bus <= 0 || pcibios_last_bus > 0xff)
        return;
    DBG("PCI: Peer bridge fixup\n");

    for (n=0; n <= pcibios_last_bus; n++)
        pcibios_scan_specific_bus(n);
}

int __init pci_legacy_init(void)
{
    if (!raw_pci_ops) {
        printk("PCI: System does not support PCI\n");
        return 0;
    }

    printk("PCI: Probing PCI hardware\n");
    pci_root_bus = pcibios_scan_root(0);
    return 0;
}

void __devinit pcibios_scan_specific_bus(int busn)
{
    int devfn;
    long node;
    u32 l;

    if (pci_find_bus(0, busn))
        return;

    node = get_mp_bus_to_node(busn);
    for (devfn = 0; devfn < 256; devfn += 8) {
        if (!raw_pci_read(0, busn, devfn, PCI_VENDOR_ID, 2, &l) &&
            l != 0x0000 && l != 0xffff) {
            DBG("Found device at %02x:%02x [%04x]\n", busn, devfn, l);
            printk(KERN_INFO "PCI: Discovered peer bus %02x\n", busn);
            pci_scan_bus_on_node(busn, &pci_root_ops, node);
            return;
        }
    }
}
EXPORT_SYMBOL_GPL(pcibios_scan_specific_bus);

int __init pci_subsys_init(void)
{
    /*
     * The init function returns an non zero value when
     * pci_legacy_init should be invoked.
     */
    if (x86_init.pci.init())
        pci_legacy_init();

    pcibios_fixup_peer_bridges();
    x86_init.pci.init_irq();
    pcibios_init();

    return 0;
}
subsys_initcall(pci_subsys_init);