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SubjectRe: [PATCH v3 00/22] PCI: Iterate pci host bridge instead of pci root bus
On Wed, Feb 6, 2013 at 1:53 AM, Mauro Carvalho Chehab
<> wrote:
> Em Tue, 5 Feb 2013 16:47:10 -0800
> Yinghai Lu <> escreveu:
>> On Tue, Feb 5, 2013 at 4:19 PM, Bjorn Helgaas <> wrote:
>> >
>> > Maybe. I'd rather not introduce for_each_pci_host_bridge() at all, if
>> > we can avoid it. Every place it's used is a place we have to audit to
>> > make sure it's safe. I think your audit above is correct and
>> > complete, but it relies on way too much architecture knowledge. It's
>> > better if we can deduce correctness without knowing which arches
>> > support hotplug and which CPUs support EDAC.
>> >
>> > As soon as for_each_pci_host_bridge() is in the tree, those uses can
>> > be copied to even more places. It's a macro, so it's usable by any
>> > module, even out-of-tree ones that we'll never see and can't fix. So
>> > we won't really have a good way to deprecate and remove it.
>> Now we only have two references in modules.
>> drivers/edac/i7core_edac.c: for_each_pci_host_bridge(host_bridge) {
>> drivers/pci/hotplug/sgi_hotplug.c: for_each_pci_host_bridge(host_bridge) {
>> for the sgi_hotplug.c, it should be same problem that have for acpiphp
>> and pciehp.
>> need to make it support pci host bridge hotplug anyway.
>> for edac, we need to check Mauro about their plan.
> The i7core_pci_lastbus() code at i7core_edac is there to make it work
> with some Nehalem/Nehalem-EP machines that hide the memory controller's
> PCI ID by using an artificially low last bus.

I don't really understand how this helps. An example would probably
make it clearer.

i7core_edac.c has some very creative use of PCI infrastructure.
Normally a driver has a pci_device_id table that identifies the
vendor/device IDs of the devices it cares about, and the driver's
.probe() method is called for every matching device.

But i7core_edac only has two entries in its id_table. When we find a
device that matches one of those two entries, we call i7core_probe(),
which then gropes around for all the *other* devices related to that
original one. This is a bit messy.

I'd like it a lot better if the device IDs in
pci_dev_descr_i7core_nehalem[], pci_dev_descr_lynnfield[], etc., were
just in the pci_device_id table directly. Then i7core_probe() would
be called directly for every device you care about, and you could sort
them out there. That should work without any need for
pci_get_device(), i7core_pci_lastbus(), etc.


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