From mboxrd@z Thu Jan 1 00:00:00 1970 From: Arnd Bergmann Subject: Re: [PATCH] PCI: add missing DT binding for linux,pci-domain property Date: Tue, 04 Nov 2014 13:07:47 +0100 Message-ID: <2606632.6m38glseTk@wuerfel> References: <1415101660-26450-1-git-send-email-l.stach@pengutronix.de> <20141104120052.GE11102@e106497-lin.cambridge.arm.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7Bit Return-path: In-Reply-To: <20141104120052.GE11102@e106497-lin.cambridge.arm.com> Sender: linux-pci-owner@vger.kernel.org To: Liviu Dudau Cc: Lucas Stach , Rob Herring , Pawel Moll , Mark Rutland , Ian Campbell , Kumar Gala , "devicetree@vger.kernel.org" , Bjorn Helgaas , "linux-pci@vger.kernel.org" List-Id: devicetree@vger.kernel.org On Tuesday 04 November 2014 12:00:52 Liviu Dudau wrote: > > While the description is potentially correct, what it fails to explain is that the > choice of using the property or generating an unstable (across boots) unique > number is actually the choice of the host bridge driver at the moment. I know that > my earlier implementations were defaulting to the automatic numbering, but that has > been dropped from the final series as Rob Herring was objecting to it. > > There is still scope to adopt a wide policy here, but for now it should say something > to the tune: > > If present this property assigns a fixed PCI domain number to a host bridge, > otherwise an unstable (across boots) unique number will be assigned. > If you decide to use the property to assign a fixed PCI domain number to a host > bridge you have to ensure that all the host bridge drivers present in the system > follow the same policy. Otherwise, potentially conflicting domain numbers > may be assigned to root busses behind different host bridges. But with the latest change to the domain handling, all drivers would implement this. I would just mention that Linux kernels older than 3.19 are probably going to ignore this property. Arnd