From mboxrd@z Thu Jan 1 00:00:00 1970 From: Christoph Hellwig Subject: Re: [PATCH] drivers/of: Introduce ARCH_HAS_OWN_OF_NUMA Date: Mon, 9 Apr 2018 10:49:18 -0700 Message-ID: <20180409174918.GA4629@infradead.org> References: <20180409074604.17671-1-oohall@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <20180409074604.17671-1-oohall@gmail.com> Sender: linux-kernel-owner@vger.kernel.org To: Oliver O'Halloran Cc: linux-kernel@vger.kernel.org, sfr@canb.auug.org.au, devicetree@vger.kernel.org, linux-nvdimm@lists.01.org, sparclinux@vger.kernel.org, linuxppc-dev@lists.ozlabs.org List-Id: devicetree@vger.kernel.org On Mon, Apr 09, 2018 at 05:46:04PM +1000, Oliver O'Halloran wrote: > Some OF platforms (pseries and some SPARC systems) has their own > implementations of NUMA affinity detection rather than using the generic > OF_NUMA driver, which mainly exists for arm64. For other platforms one > of two fallbacks provided by the base OF driver are used depending on > CONFIG_NUMA. > > In the CONFIG_NUMA=n case the fallback is an inline function in of.h. > In the =y case the fallback is a real function which is defined as a > weak symbol so that it may be overwritten by the architecture if desired. > > The problem with this arrangement is that the real implementations all > export of_node_to_nid(). Unfortunately it's not possible to export the > fallback since it would clash with the non-weak version. As a result > we get build failures when: > > a) CONFIG_NUMA=y && CONFIG_OF=y, and > b) The platform doesn't implement of_node_to_nid(), and > c) A module uses of_node_to_nid() > > Given b) will be true for most platforms this is fairly easy to hit > and has been observed on ia64 and x86. > > This patch remedies the problem by introducing the ARCH_HAS_OWN_OF_NUMA > Kconfig option which is selected if an architecture provides an > implementation of of_node_to_nid(). If a platform does not use it's own, > or the generic OF_NUMA, then always use the inline fallback in of.h so > we don't need to futz around with exports. I'd rather have a specific kconfig symbol for the 'generic' implementation, especially given that it doesn't appear to be all that generic.