From mboxrd@z Thu Jan 1 00:00:00 1970 From: Michael Ellerman Subject: Re: [PATCH 16/67] powerpc: rename dma_direct_ to dma_nommu_ Date: Wed, 03 Jan 2018 17:24:02 +1100 Message-ID: <87h8s3cvel.fsf@concordia.ellerman.id.au> References: <20171229081911.2802-1-hch@lst.de> <20171229081911.2802-17-hch@lst.de> <878tdgtwzp.fsf@concordia.ellerman.id.au> Mime-Version: 1.0 Content-Type: text/plain Return-path: In-Reply-To: Sender: linux-m68k-owner@vger.kernel.org List-Id: linux-m68k@vger.kernel.org To: Geert Uytterhoeven Cc: Christoph Hellwig , iommu@lists.linux-foundation.org, Linux MIPS Mailing List , linux-ia64@vger.kernel.org, Linux-sh list , sparclinux , Guan Xuetao , Linux-Arch , linux-s390 , linux-c6x-dev@linux-c6x.org, "open list:QUALCOMM HEXAGON..." , the arch/x86 maintainers , arcml , adi-buildroot-devel@lists.sourceforge.net, linux-m68k , patches@groups.riscv.org, "open list:METAG ARCHITECTURE" , linux-arm-kernel@lists.infradead.org, Michal Geert Uytterhoeven writes: > On Tue, Jan 2, 2018 at 10:45 AM, Michael Ellerman wrote: >> Christoph Hellwig writes: >> >>> We want to use the dma_direct_ namespace for a generic implementation, >>> so rename powerpc to the second best choice: dma_nommu_. >> >> I'm not a fan of "nommu". Some of the users of direct ops *are* using an >> IOMMU, they're just setting up a 1:1 mapping once at init time, rather >> than mapping dynamically. >> >> Though I don't have a good idea for a better name, maybe "1to1", >> "linear", "premapped" ? > > "identity"? I think that would be wrong, but thanks for trying to help :) The address on the device side is sometimes (often?) offset from the CPU address. So eg. the device can DMA to RAM address 0x0 using address 0x800000000000000. Identity would imply 0 == 0 etc. I think "bijective" is the correct term, but that's probably a bit esoteric. cheers