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[209.85.128.49]) by smtp.gmail.com with ESMTPSA id h10sm1684357eds.0.2020.08.20.10.41.17 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 20 Aug 2020 10:41:18 -0700 (PDT) Received: by mail-wm1-f49.google.com with SMTP id k8so2418457wma.2 for ; Thu, 20 Aug 2020 10:41:17 -0700 (PDT) X-Received: by 2002:a1c:4d12:: with SMTP id o18mr4512279wmh.55.1597945276327; Thu, 20 Aug 2020 10:41:16 -0700 (PDT) MIME-Version: 1.0 References: <20200819065555.1802761-1-hch@lst.de> <20200819065555.1802761-6-hch@lst.de> <62e4f4fc-c8a5-3ee8-c576-fe7178cb4356@arm.com> <2b32f1d8-16f7-3352-40a5-420993d52fb5@arm.com> <20200820050214.GA4815@lst.de> <20200820165213.GC12693@lst.de> In-Reply-To: <20200820165213.GC12693@lst.de> From: Tomasz Figa Date: Thu, 20 Aug 2020 19:41:03 +0200 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH 05/28] media/v4l2: remove V4L2-FLAG-MEMORY-NON-CONSISTENT To: Christoph Hellwig Cc: alsa-devel@alsa-project.org, linux-ia64@vger.kernel.org, Linux Doc Mailing List , nouveau@lists.freedesktop.org, linux-nvme@lists.infradead.org, linux-mips@vger.kernel.org, "James E.J. Bottomley" , linux-mm@kvack.org, linux-samsung-soc , Joonyoung Shim , linux-scsi@vger.kernel.org, "list@263.net:IOMMU DRIVERS" , Ben Skeggs , Matt Porter , Linux Media Mailing List , Tom Lendacky , Pawel Osciak , Mauro Carvalho Chehab , "list@263.net:IOMMU DRIVERS , Joerg Roedel , " , Thomas Bogendoerfer , linux-parisc@vger.kernel.org, netdev@vger.kernel.org, Seung-Woo Kim , Linux Kernel Mailing List , Kyungmin Park , Robin Murphy X-BeenThere: iommu@lists.linux-foundation.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: Development issues for Linux IOMMU support List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: iommu-bounces@lists.linux-foundation.org Sender: "iommu" On Thu, Aug 20, 2020 at 6:52 PM Christoph Hellwig wrote: > > On Thu, Aug 20, 2020 at 12:24:31PM +0200, Tomasz Figa wrote: > > > Of course this still uses the scatterlist structure with its annoying > > > mix of input and output parametes, so I'd rather not expose it as > > > an official API at the DMA layer. > > > > The problem with the above open coded approach is that it requires > > explicit handling of the non-IOMMU and IOMMU cases and this is exactly > > what we don't want to have in vb2 and what was actually the job of the > > DMA API to hide. Is the plan to actually move the IOMMU handling out > > of the DMA API? > > > > Do you think we could instead turn it into a dma_alloc_noncoherent() > > helper, which has similar semantics as dma_alloc_attrs() and handles > > the various corner cases (e.g. invalidate_kernel_vmap_range and > > flush_kernel_vmap_range) to achieve the desired functionality without > > delegating the "hell", as you called it, to the users? > > Yes, I guess I could do something in that direction. At least for > dma-iommu, which thanks to Robin should be all you'll need in the > foreseeable future. That would be really great. Let me know if we can help by testing with V4L2/vb2 or in any other way. Best regards, Tomasz _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu