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    SubjectRe: [PATCH] 2.6 SGI Altix I/O code reorganization
    Grant Grundler wrote:

    > Colin,
    > thanks for ACKing the feedback.
    > I think there is still some confusion...
    >
    > On Wed, Oct 06, 2004 at 02:09:54PM -0500, Colin Ngam wrote:
    > ...
    > > > Mathew explained replacing the raw_pci_ops pointer is the Right Thing
    > > > and I suspect it's easier to properly implement.
    > >
    > > I believe we did just that. We did not touch pci_root_ops.
    >
    > Correct. The patch ignores/overides pci_root_ops with sn_pci_root_ops
    > (which is what I originally suggested).
    >
    > Mathew's point was only raw_pci_ops needs to point at a different
    > set of struct pci_raw_ops (see include/linux/pci.h).

    Hi Grant,

    Well, I am confused then.

    Originally, we needed to use pci_root_ops in io_init.c to pass it to
    pci_scan_bus(). But pci_root_ops is defined as a static in pci/pci.c. We took
    out the static so that we can use this in io_init.c. However, it sounded like
    you guys do not want to externalize pci_root_ops. Okay, we created
    sn_pci_root_ops.

    We do not want pci_raw_ops to point at anything different. It is exactly what we
    needed now that we have implemented in our Prom all the pci config read/write SAL
    calls.

    >
    >
    > > > I realize that's not easy to add/maintain in the arch/ia64 port though
    > > > since pcibios_fixup_bus() is common code for multiple platforms.
    > >
    > > Yes, would anybody allow us to make a platform specific callout
    > > from within generic pcibios_fixup_bus()???
    >
    > If it can be avoided, preferably not. But that's up to Jesse/Tony I think.
    >
    > ...
    > > > It means we are telling PCI subsystem to walk root busses that don't
    > > > exist in all configurations. I hope there are no nasty side effects
    > > > from that.
    > >
    > > Not at all. If you look at the loop, sn_pci_fixup_bus(0 gets called for 0 -
    > > PCI_BUSES_TO_SCAN but if the bus does not exist,
    >
    > Can you quote the bit of the patch which implements "if the bus does not
    > exist" check?
    > I can't find it.

    In the routine sn_pci_fixup_bus()

    +static void sn_pci_fixup_bus(int segment, int busnum)
    +{
    + int status = 0;
    + int nasid, cnode;
    + struct pci_bus *bus;
    + struct pci_controller *controller;
    + struct pcibus_bussoft *prom_bussoft_ptr;
    + struct hubdev_info *hubdev_info;
    + void *provider_soft;
    +
    + status =
    + sal_get_pcibus_info((u64) segment, (u64) busnum,
    + (u64) ia64_tpa(&prom_bussoft_ptr));
    + if (status > 0) {
    + return; /* bus # does not exist */
    + }
    +
    + prom_bussoft_ptr = __va(prom_bussoft_ptr);
    + controller = sn_alloc_pci_sysdata();
    + if (!controller) {
    + BUG();
    + }
    +
    + bus = pci_scan_bus(busnum, &sn_pci_root_ops, controller);
    + if (bus == NULL) {
    + return; /* error, or bus already scanned */
    + }

    We bail if sal_get_pcibus_info() is not successful. Am I missing something?

    >
    >
    > > One favour. Would you agree to letting this patch be included by Tony
    > > and we will come up with another patch to fix the 2 obvious items listed
    > > above? It will be great to avoid spinning this big patch.
    >
    > I think that's up to Jesse/Tony.
    > I don't "own" any of the code in question.
    > Just trying to undo the confusion I caused.

    Thanks.

    colin

    >
    >
    > grant

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