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, 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 7B6A9C19425 for ; Wed, 9 Dec 2020 11:17:27 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4C9AC23B85 for ; Wed, 9 Dec 2020 11:17:27 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730565AbgLILRX (ORCPT ); Wed, 9 Dec 2020 06:17:23 -0500 Received: from verein.lst.de ([213.95.11.211]:49769 "EHLO verein.lst.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726954AbgLILRX (ORCPT ); Wed, 9 Dec 2020 06:17:23 -0500 Received: by verein.lst.de (Postfix, from userid 2407) id B68FB68AFE; Wed, 9 Dec 2020 12:16:39 +0100 (CET) Date: Wed, 9 Dec 2020 12:16:39 +0100 From: ". Christoph Hellwig" To: Sergey Senozhatsky Cc: Tomasz Figa , ". Christoph Hellwig" , Ricardo Ribalda , Marek Szyprowski , Robin Murphy , Mauro Carvalho Chehab , IOMMU DRIVERS , Joerg Roedel , Linux Doc Mailing List , Linux Kernel Mailing List , Linux Media Mailing List , Sergey Senozhatsky Subject: Re: [PATCH v3 5/6] media: uvcvideo: Use dma_alloc_noncontiguos API Message-ID: <20201209111639.GB22806@lst.de> References: <20201125221917.150463-1-ribalda@chromium.org> <20201130083410.GD32234@lst.de> <20201201033658.GE3723071@google.com> <20201201144916.GA14682@lst.de> <20201208071320.GA1667627@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20201208071320.GA1667627@google.com> User-Agent: Mutt/1.5.17 (2007-11-01) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Dec 08, 2020 at 04:13:20PM +0900, Sergey Senozhatsky wrote: > On (20/12/08 13:54), Tomasz Figa wrote: > > > > In any case, Sergey is going to share a preliminary patch on how the > > current API would be used in the V4L2 videobuf2 framework. That should > > give us more input on how such a helper could look. > > HUGE apologies for the previous screw up! I replied in the > gmail web-interface and that did not work out as expected > (at all, big times). Actually the previous mail was a mime multipart one, and the plain text version displayed just fine here. My the gmail engineers finally learned something after all. > Another thing to notice is that the new API requires us to have two execution branches > in allocators - one for the current API; and one for the new API (if it's supported and > if user-space requested non-coherent allocation). So I think we do want these branches for coherent vs non-coherent as they have very different semantics and I do not think that hiding them under the same API helps people to understand those vastly different semantics. OTOH we should look into a fallback for DMA API instances that do not support the discontigous allocations. I think between your comments and those from Ricardo I have a good idea for a somewhat updated API. I'll try to post something in the next days.