From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-5.2 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 54AECC433DF for ; Fri, 21 Aug 2020 08:00:25 +0000 (UTC) Received: from alsa0.perex.cz (alsa0.perex.cz [77.48.224.243]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id D091220732 for ; Fri, 21 Aug 2020 08:00:24 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=alsa-project.org header.i=@alsa-project.org header.b="MVWi+eQC" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org D091220732 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=lst.de Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=alsa-devel-bounces@alsa-project.org Received: from alsa1.perex.cz (alsa1.perex.cz [207.180.221.201]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by alsa0.perex.cz (Postfix) with ESMTPS id 3B00C16CE; Fri, 21 Aug 2020 09:59:33 +0200 (CEST) DKIM-Filter: OpenDKIM Filter v2.11.0 alsa0.perex.cz 3B00C16CE DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=alsa-project.org; s=default; t=1597996823; bh=X0ORiFKrWP0s649SyWVIij8iYQogdHWVg0rWlAHt9tU=; h=Date:From:To:Subject:References:In-Reply-To:Cc:List-Id: List-Unsubscribe:List-Archive:List-Post:List-Help:List-Subscribe: From; b=MVWi+eQC8jPpmqGxMcakCY7W6XenOemc4McniqEWZJmVJHbyNTXVXUJC7IuIEBWWX wn5TOiD/J1Ka+62LAo7ksXJqJi8WlE2X6XN6Kjx1xswd9JFwBiuhbRZarnMMHfFB+R O7qMiXDIbadOnJ0UZVzw4dlauuP15bzZvQvF3f1U= Received: from alsa1.perex.cz (localhost.localdomain [127.0.0.1]) by alsa1.perex.cz (Postfix) with ESMTP id C7422F804CF; Fri, 21 Aug 2020 09:37:04 +0200 (CEST) Received: by alsa1.perex.cz (Postfix, from userid 50401) id 74FCAF80228; Thu, 20 Aug 2020 18:52:16 +0200 (CEST) Received: from verein.lst.de (verein.lst.de [213.95.11.211]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by alsa1.perex.cz (Postfix) with ESMTPS id 3DDF7F800D3 for ; Thu, 20 Aug 2020 18:52:14 +0200 (CEST) DKIM-Filter: OpenDKIM Filter v2.11.0 alsa1.perex.cz 3DDF7F800D3 Received: by verein.lst.de (Postfix, from userid 2407) id 48F9168AFE; Thu, 20 Aug 2020 18:52:13 +0200 (CEST) Date: Thu, 20 Aug 2020 18:52:13 +0200 From: Christoph Hellwig To: Tomasz Figa Subject: Re: [PATCH 05/28] media/v4l2: remove V4L2-FLAG-MEMORY-NON-CONSISTENT Message-ID: <20200820165213.GC12693@lst.de> 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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.17 (2007-11-01) X-Mailman-Approved-At: Fri, 21 Aug 2020 09:36:15 +0200 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, Christoph Hellwig , Marek Szyprowski , linux-samsung-soc , Joonyoung Shim , linux-scsi@vger.kernel.org, Joerg Roedel , "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: alsa-devel@alsa-project.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: "Alsa-devel mailing list for ALSA developers - http://www.alsa-project.org" List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: alsa-devel-bounces@alsa-project.org Sender: "Alsa-devel" 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.