[PATCH v6 03/30] PCI: Export busn_resource to drivers/pci

Yijing Wang wangyijing at huawei.com
Thu Mar 12 18:57:25 PDT 2015

>> Hi Bjorn, busn_resource may would not be shared by multi domains,
>> We insert bus number resource like:
>> pci_add_resource(&resources, &busn_resource);	
>> 	pci_bus_insert_busn_res(root_bus, start, bus_max);	//start is the root bus number provided by arch pci host driver, bus max here == 255
>> 		get_pci_domain_busn_res(domain)	//for root bus	//try to get a domain specific pci_domain_busn_res, if not exist, create it.
>> 			request_resource_conflict(domain_specific_busn_res, res)   //request busn res(start, bus_max) from the pci_domain_busn_res.
>> So every domain has its own pci_domain_busn_res , different domain would not share the same bus number resource.
> The intent of pci_add_resource() and passing the resulting resource list
> into pci_scan_root_bus(), etc., is that the host bridge may consume any
> resources described by the list.  If we pass the same resource to multiple
> calls, that means the resource must be shared between the multiple host
> bridges involved.  For bus numbers, that makes some sense if the platform
> considers the bridges to be in the same domain, but not if they are in
> different domains.
> If we export busn_resource, we have no control over what domains it becomes
> associated with because the domain is passed into pci_scan_root_bus() by
> the caller.

Agree, I will drop this patch, thanks!

> Bjorn
> .


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