linux-kernel - Re: [PATCH v2 06/29] x86/PCI: convert to pci_create_root_bus() and pci_scan_root

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Date:	Fri, 14 Oct 2011 14:54:46 -0600
From:	Bjorn Helgaas <bhelgaas@...gle.com>
To:	Yinghai Lu <yinghai.lu@...cle.com>
Cc:	linux-pci@...r.kernel.org, linux-arch@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Jesse Barnes <jbarnes@...tuousgeek.org>
Subject: Re: [PATCH v2 06/29] x86/PCI: convert to pci_create_root_bus() and pci_scan_root_bus()

On Fri, Oct 14, 2011 at 2:39 PM, Yinghai Lu <yinghai.lu@...cle.com> wrote:
> On 10/14/2011 01:32 PM, Bjorn Helgaas wrote:
>
>
>>>>       int node;
>>>> @@ -353,11 +349,18 @@ struct pci_bus * __devinit pci_acpi_scan_root(struct acpi_pci_root *root)
>>>>               memcpy(bus->sysdata, sd, sizeof(*sd));
>>>>               kfree(sd);
>>>>       } else {
>>>> -             bus = pci_create_bus(NULL, busnum, &pci_root_ops, sd);
>>>> -             if (bus) {
>>>> -                     get_current_resources(device, busnum, domain, bus);
>>>> -                     bus->subordinate = pci_scan_child_bus(bus);
>>>> +             INIT_LIST_HEAD(&resources);
>>>> +             get_current_resources(device, busnum, domain, &resources);
>>>> +             if (!pci_use_crs) {
>>>> +                     pci_free_resource_list(&resources);
>>>> +                     x86_pci_root_bus_resources(busnum, &resources);
>>>>               }
>>>
>>>
>>> You may need to update get_current_resources() to return status about handling _CRS...
>>> and check that status insteaf of !pci_use_crs.
>>
>> Is the current patch broken here?  I don't think it will be simpler to
>> have get_current_resources() return a status and check that.  But if
>> something's actually broken, I want to fix it, of course.
>>
>
>
> yes. if for some reason, _CRS is not handled right, that root bus resources will not get set to default res.
>
> +             status = get_current_resources(device, busnum, domain, &resources);
> +             if (status) {
> +                     pci_free_resource_list(&resources);
> +                     x86_pci_root_bus_resources(busnum, &resources);
>              }
>
> get_current_resources() will not return 0 if _CRS is not really used.

OK.  I think it was that way before, too.  We created the bus with
default resources, but the first thing get_current_resources() did was
clear them all out.  If there was a problem parsing _CRS, we never
went back and put the defaults back in.

But I think this will do what you suggest and is nicer than what I had before:

                INIT_LIST_HEAD(&resources);
                get_current_resources(device, busnum, domain, &resources);
                if (list_empty(&resources))
                        x86_pci_root_bus_resources(busnum, &resources);
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