From: Russell King - ARM Linux Subject: Re: [V4 PATCH 3/6] pci: Generic function for setting up PCI device DMA coherency Date: Wed, 20 May 2015 21:46:45 +0100 Message-ID: <20150520204645.GX2067@n2100.arm.linux.org.uk> References: <1431724994-21601-1-git-send-email-Suravee.Suthikulpanit@amd.com> <3954735.qeaTp8qOcM@vostro.rjw.lan> <20150520092415.GA25313@e104818-lin.cambridge.arm.com> <2072233.lIH4idDurI@wuerfel> <20150520093401.GC25313@e104818-lin.cambridge.arm.com> <555C7759.3040304@amd.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Catalin Marinas , Arnd Bergmann , thomas.lendacky@amd.com, herbert@gondor.apana.org.au, al.stone@linaro.org, linaro-acpi@lists.linaro.org, netdev@vger.kernel.org, will.deacon@arm.com, linux-kernel@vger.kernel.org, Rob Herring , davem@davemloft.net, linux-acpi@vger.kernel.org, Murali Karicheri , "Rafael J. Wysocki" , hanjun.guo@linaro.org, msalter@redhat.com, grant.likely@linaro.org, leo.duran@amd.com, lenb@kernel.org, bhelgaas@google.com, David Woodhouse , linux-arm-kernel@lists.infradead.org, linux-crypto@vger.kernel.org To: Suravee Suthikulanit Return-path: Content-Disposition: inline In-Reply-To: <555C7759.3040304@amd.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-crypto.vger.kernel.org On Wed, May 20, 2015 at 07:00:25AM -0500, Suravee Suthikulanit wrote: > On 5/20/2015 4:34 AM, Catalin Marinas wrote: > >We have a dummy of_dma_configure() already when !CONFIG_OF, otherwise > >we would need #ifndef here. I already replied, I think for other > >architectures we need this check to avoid a useless host->of_node test. > > It seems that there are several places that have similar check. Would it be > good to convert this into a macro? Something like: > > #define OF_NODE_ENABLED(dev) (IS_ENABLED(CONFIG_OF) && dev->of_node) This /could/ be a useful compile-time optimisation: when CONFIG_OF is disabled, dev->of_node exists but will always be NULL - but the compiler doesn't know this. Your suggestion above would tell the compiler that when CONFIG_OF is disabled, OF_NODE_ENABLED() will evaluate to a constant false, which means it can eliminate code. -- FTTC broadband for 0.8mile line: currently at 10.5Mbps down 400kbps up according to speedtest.net.