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[209.85.166.50]) by smtp.gmail.com with ESMTPSA id 14sm4659188ilz.7.2021.01.07.06.14.19 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 07 Jan 2021 06:14:19 -0800 (PST) Received: by mail-io1-f50.google.com with SMTP id m23so6295072ioy.2 for ; Thu, 07 Jan 2021 06:14:19 -0800 (PST) X-Received: by 2002:a6b:cd02:: with SMTP id d2mr1461830iog.4.1610028858785; Thu, 07 Jan 2021 06:14:18 -0800 (PST) MIME-Version: 1.0 References: <20201125221917.150463-1-ribalda@chromium.org> <20201130083410.GD32234@lst.de> <20201201033658.GE3723071@google.com> <20201201144916.GA14682@lst.de> <20201208071320.GA1667627@google.com> <20201209111639.GB22806@lst.de> In-Reply-To: <20201209111639.GB22806@lst.de> From: Ricardo Ribalda Date: Thu, 7 Jan 2021 15:14:08 +0100 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH v3 5/6] media: uvcvideo: Use dma_alloc_noncontiguos API To: ". Christoph Hellwig" Cc: Sergey Senozhatsky , Tomasz Figa , 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 Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Christoph Happy new year! On Wed, Dec 9, 2020 at 12:16 PM . Christoph Hellwig wrote: > > 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. Did you have time to look into this? No hurry, I just want to make sure that I didn't miss anything ;) Best regards! -- Ricardo Ribalda