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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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