From mboxrd@z Thu Jan 1 00:00:00 1970 From: Julian Calaby Subject: Re: [PATCH 16/67] powerpc: rename dma_direct_ to dma_nommu_ Date: Wed, 3 Jan 2018 19:19:46 +1100 Message-ID: References: <20171229081911.2802-1-hch@lst.de> <20171229081911.2802-17-hch@lst.de> <878tdgtwzp.fsf@concordia.ellerman.id.au> <87h8s3cvel.fsf@concordia.ellerman.id.au> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Return-path: In-Reply-To: Sender: linux-m68k-owner@vger.kernel.org List-Id: linux-m68k@vger.kernel.org To: Geert Uytterhoeven Cc: Michael Ellerman , 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" Maili Hi All, On Wed, Jan 3, 2018 at 6:49 PM, Geert Uytterhoeven wrote: > Hi Michael, > > On Wed, Jan 3, 2018 at 7:24 AM, Michael Ellerman wrote: >> 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. > > OK, didn't know about the offset. > Then "linear" is what we tend to use, right? If this is indeed a linear mapping, can we just remove this and replace it with the new "generic" mapping being introduced by this patchset? Thanks, -- Julian Calaby Email: julian.calaby@gmail.com Profile: http://www.google.com/profiles/julian.calaby/