On 2015/10/8 21:20, Bjorn Helgaas wrote:
> On Thu, Oct 08, 2015 at 01:32:04PM +0800, Jiang Liu wrote:
>> On 2015/10/7 1:47, Bjorn Helgaas wrote:
>>>> +struct pci_bus *acpi_pci_root_create(struct acpi_pci_root *root,
>>>> + struct acpi_pci_root_ops *ops,
>>>> + struct acpi_pci_root_info *info,
>>>> + void *sysdata)
>>>> +{
>>>> + int ret, busnum = root->secondary.start;
>>>> + struct acpi_device *device = root->device;
>>>> + int node = acpi_get_node(device->handle);
>>>> + struct pci_bus *bus;
>>>> +
>>>> + info->root = root;
>>>> + info->bridge = device;
>>>> + info->ops = ops;
>>>> + INIT_LIST_HEAD(&info->resources);
>>>> + snprintf(info->name, sizeof(info->name), "PCI Bus %04x:%02x",
>>>> + root->segment, busnum);
>>>> +
>>>> + if (ops->init_info && ops->init_info(info))
>>>> + goto out_release_info;
>>>> + ret = acpi_pci_probe_root_resources(info);
>>>> + if (ops->prepare_resources)
>>>> + ret = ops->prepare_resources(info, ret);
>>>> + if (ret < 0)
>>>> + goto out_release_info;
>>>> + else if (ret > 0)
>>>> + pci_acpi_root_add_resources(info);
>>>
>>> This is unnecessarily complicated: you set "ret", then overwrite it if
>>> ops->prepare_resources. By the time you test "ret", it's messy to
>>> figure out what it means.
>>>
>>> Both ops->prepare_resources() and pci_acpi_root_add_resources()
>>> should be able to deal with empty resource lists, so can you do the
>>> following instead?
>>>
>>> ret = acpi_pci_probe_root_resources(info);
>>> if (ret < 0)
>>> goto out_release_info;
>>
>> The original code is used to handle a special case for x86,
>> where acpi_pci_probe_root_resources() fails but ops->prepare_resources()
>> succeeds. For x86, PCI host bridge resources may probed by means
>> other than ACPI when pci_use_crs is true (AMD and Broadcom hostbridges).
>> So we can't return failure when acpi_pci_probe_root_resources() fails.
>
> That's even worse than I thought. I take back my ack; I think this
> really needs to be restructured so it does the right thing *and* reads
> clearly. Having convoluted generic code to deal with an arch-specific
> special case is a recipe for breakage in the future.
>
> Maybe you can move the non-ACPI resource probing from
> prepare_resources() into acpi_pci_probe_root_resources() (you could
> rename it to something more generic if that helps).
Hi Bjorn,
How about this solution?
1) export acpi_pci_probe_root_resources() as a helper to arch code
2) change ACPI core code as below
if (ops->init_info && ops->init_info(info))
goto out_release_info;
if (ops->prepare_resources)
ret = ops->prepare_resources(info);
else
ret = acpi_pci_probe_root_resources(info);
if (ret < 0)
goto out_release_info;
pci_acpi_root_add_resources(info);
pci_add_resource(&info->resources, &root->secondary);
bus = pci_create_root_bus(NULL, busnum, ops->pci_ops,
sysdata, &info->resources);
if (!bus)
goto out_release_info;
By this way, if arch has special requirement, it could implement
prepare_resources callback and make use of
acpi_pci_probe_root_resources() if needed.
Thanks!
Gerry
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