linux-kernel - Re: [PATCH v10 07/10] OF: Introduce helper function for getting PCI domain

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Tue, 9 Sep 2014 08:17:50 -0600
From:	Bjorn Helgaas <bhelgaas@...gle.com>
To:	Arnd Bergmann <arnd@...db.de>
Cc:	Liviu Dudau <Liviu.Dudau@....com>,
	Yijing Wang <wangyijing@...wei.com>,
	Rob Herring <robherring2@...il.com>,
	Rob Herring <robh+dt@...nel.org>,
	Jason Gunthorpe <jgunthorpe@...idianresearch.com>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Catalin Marinas <Catalin.Marinas@....com>,
	Will Deacon <Will.Deacon@....com>,
	Russell King <linux@....linux.org.uk>,
	linux-pci <linux-pci@...r.kernel.org>,
	Linus Walleij <linus.walleij@...aro.org>,
	Tanmay Inamdar <tinamdar@....com>,
	Grant Likely <grant.likely@...retlab.ca>,
	Sinan Kaya <okaya@...eaurora.org>,
	Jingoo Han <jg1.han@...sung.com>,
	Kukjin Kim <kgene.kim@...sung.com>,
	Suravee Suthikulanit <suravee.suthikulpanit@....com>,
	linux-arch <linux-arch@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Device Tree ML <devicetree@...r.kernel.org>,
	LAKML <linux-arm-kernel@...ts.infradead.org>,
	"grant.likely@...aro.org" <grant.likely@...aro.org>
Subject: Re: [PATCH v10 07/10] OF: Introduce helper function for getting PCI domain_nr

On Tue, Sep 9, 2014 at 3:16 AM, Arnd Bergmann <arnd@...db.de> wrote:
> On Tuesday 09 September 2014 09:46:21 Liviu Dudau wrote:
>> On Tue, Sep 09, 2014 at 06:54:21AM +0100, Yijing Wang wrote:
>> > PCI domain(or named segment) is provided by firmware, in ACPI system, we evaluated it
>> > by method "_SEG". in IA64 with ACPI, PCI hostbridge driver retrieves the domain from ACPI,
>> > if it's absent, the default domain is zero. So I wonder why in DTS, if it's absent, we get
>> > a auto increment domain value.
>>
>> Because you can have more than one hostbridge (rare, but not impossible) and unless you
>> want to join the two segments, you might want to give it a different domain.
>
> I think you misunderstood the question. The difference is that in ACPI you
> are required to specify the domain, while in DT it is optional with your
> implementation.

_SEG is actually optional, but the spec (ACPI r5.0, sec 6.5.6) says to
assume domain 0 if _SEG is absent.

Yijing mentioned ia64, which is relevant because PCI config accesses
on ia64 are done via a firmware (SAL) interface, and the domain is
part of that interface, so the kernel is actually required to supply
the correct domain number (0 or _SEG value) for each host bridge.

Bjorn
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/