Re: [RFC PATCH 01/16] PCI: Enhance pci_scan_root_bus() to support default IO/MEM resources

[Yijing Wang <wangyijing@huawei.com>]

On 2014/11/18 22:23, Liviu Dudau wrote:
> On Tue, Nov 18, 2014 at 11:46:06AM +0000, Yijing Wang wrote:
>> On 2014/11/18 17:36, Arnd Bergmann wrote:
>>> On Tuesday 18 November 2014 15:44:23 Yijing Wang wrote:
>>>> On 2014/11/17 18:08, Arnd Bergmann wrote:
>>>>> On Monday 17 November 2014 18:21:35 Yijing Wang wrote:
>>>>>> -       list_for_each_entry(window, resources, list)
>>>>>> -               if (window->res->flags & IORESOURCE_BUS) {
>>>>>> -                       found = true;
>>>>>> -                       break;
>>>>>> -               }
>>>>>> +       if (!resources) {
>>>>>> +               pci_add_resource(&default_res, &ioport_resource);
>>>>>> +               pci_add_resource(&default_res, &iomem_resource);
>>>>>> +               pci_add_resource(&default_res, &busn_resource);
>>>>>> +       } else {
>>>>>>
>>>>>
>>>>> Isn't it almost always wrong to do this? You are adding all of the
>>>>> I/O ports and memory to the host bridge, which will prevent you from
>>>>> adding another host bridge, and the iomem_resource normally
>>>>> includes a lot of addresses that are not accessible by the PCI host.
>>>>
>>>> Hi Arnd, pci host bridge windows are the ranges allow child devices to setup
>>>> from. Add all of IO/MEM here just a limit to child devices, no request for these
>>>> resources, so it won't hurt another host bridge. Some platforms have no dts or ACPI
>>>> report host bridge resources, in this case, we directly assign ioport/iomem_resources
>>>> as the root resources of PCI devices.
>>>
>>> But it would be wrong to allow hosts to allocate a device BAR that is not
>>> visible through the host bridge. I think we need to keep these separate
>>> from the general case: if you call any of the modern interfaces you have
>>> to provide the resources and a device. I notice that there is only one
>>> caller of pci_scan_bus_parented(), we should probably change that over to
>>> pci_scan_root_bus() or your new interface and remove the old one, but
>>> keep pci_scan_bus() as the only entry point for all of the legacy users
>>> that do not know about the resources.
>>
>> Ok, I will move this out of the generic interface.
> 
> My suggestion would actually be to trigger a warning/error if you detect that the resources
> are missing. That way we can force the drivers to clean up.

It make sense to me, thanks.

> 
> Best regards,
> Liviu
> 
>>
>> Thanks!
>> Yijing.
>>
>>>
>>> 	Arnd
>>>
>>> .
>>>
>>
>>
>> -- 
>> Thanks!
>> Yijing
>>
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> 


-- 
Thanks!
Yijing