From mboxrd@z Thu Jan  1 00:00:00 1970
From: wangyijing@huawei.com (Yijing Wang)
Date: Thu, 12 Mar 2015 19:42:25 +0800
Subject: [PATCH v6 03/30] PCI: Export busn_resource to drivers/pci
In-Reply-To: <20150311222835.GA1082@google.com>
References: <1425868467-9667-1-git-send-email-wangyijing@huawei.com>
 <1425868467-9667-4-git-send-email-wangyijing@huawei.com>
 <20150311222835.GA1082@google.com>
Message-ID: <55017BA1.7020700@huawei.com>
To: linux-arm-kernel@lists.infradead.org
List-Id: linux-arm-kernel.lists.infradead.org

>> -static struct resource busn_resource = {
>> +struct resource busn_resource = {
>>  	.name	= "PCI busn",
>>  	.start	= 0,
>>  	.end	= 255,
>>  	.flags	= IORESOURCE_BUS,
>>  };
>> +EXPORT_SYMBOL(busn_resource);
> 
> I don't think this is a good idea.  We support multiple PCI domains, and
> each domain has its own 0-255 bus number range.  This busn_resource is
> only for domain 0 and probably should be handled in arch code instead of
> the PCI core.
> 
> Right now, I think it's possible to call pci_scan_bus_parented() or
> pci_scan_bus() several times for buses in different domains, and they would
> all share the same busn_resource, which would cause corruption.
> 
> So it's already broken, but I don't want to make it harder to fix by
> exporting this stuff.

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.

Do I understand correct ?

Thanks!
Yijing.

> 
>>  
>>  /* Ugh.  Need to stop exporting this to modules. */
>>  LIST_HEAD(pci_root_buses);
>> -- 
>> 1.7.1
>>
> 
> .
> 


-- 
Thanks!
Yijing