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Message-ID: <55024405.8040504@huawei.com>
Date: Fri, 13 Mar 2015 09:57:25 +0800
From: Yijing Wang <wangyijing@huawei.com>
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To: Bjorn Helgaas <bhelgaas@google.com>
CC: Jiang Liu <jiang.liu@linux.intel.com>, <linux-pci@vger.kernel.org>,
        Yinghai Lu <yinghai@kernel.org>, <linux-kernel@vger.kernel.org>,
        Marc Zyngier <marc.zyngier@arm.com>,
        <linux-arm-kernel@lists.infradead.org>,
        Russell King <linux@arm.linux.org.uk>, <x86@kernel.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Benjamin Herrenschmidt <benh@kernel.crashing.org>,
        Rusty Russell <rusty@rustcorp.com.au>, Tony Luck <tony.luck@intel.com>,
        <linux-ia64@vger.kernel.org>, "David S. Miller" <davem@davemloft.net>,
        "Guan Xuetao" <gxt@mprc.pku.edu.cn>, <linux-alpha@vger.kernel.org>,
        <linux-m68k@vger.kernel.org>, Liviu Dudau <liviu@dudau.co.uk>,
        "Arnd Bergmann" <arnd@arndb.de>,
        Geert Uytterhoeven <geert@linux-m68k.org>
Subject: Re: [PATCH v6 03/30] PCI: Export busn_resource to drivers/pci
References: <1425868467-9667-1-git-send-email-wangyijing@huawei.com> <1425868467-9667-4-git-send-email-wangyijing@huawei.com> <20150311222835.GA1082@google.com> <55017BA1.7020700@huawei.com> <20150312193219.GA7346@google.com>
In-Reply-To: <20150312193219.GA7346@google.com>
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>> 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
> 
> .
> 


-- 
Thanks!
Yijing