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[209.85.221.51]) by smtp.gmail.com with ESMTPSA id j22sm1208019edp.77.2020.10.07.05.21.54 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 07 Oct 2020 05:21:55 -0700 (PDT) Received: by mail-wr1-f51.google.com with SMTP id n18so1920553wrs.5 for ; Wed, 07 Oct 2020 05:21:54 -0700 (PDT) X-Received: by 2002:adf:f2ce:: with SMTP id d14mr2420557wrp.32.1602073314520; Wed, 07 Oct 2020 05:21:54 -0700 (PDT) MIME-Version: 1.0 References: <20200930160917.1234225-1-hch@lst.de> <20200930160917.1234225-9-hch@lst.de> <20201002175040.GA1131147@chromium.org> <20201005082629.GA13850@lst.de> <20201007062150.GA10601@lst.de> In-Reply-To: <20201007062150.GA10601@lst.de> From: Tomasz Figa Date: Wed, 7 Oct 2020 14:21:43 +0200 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH 8/8] WIP: add a dma_alloc_contiguous API To: Christoph Hellwig Cc: Sergey Senozhatsky , Mauro Carvalho Chehab , Marek Szyprowski , "open list:IOMMU DRIVERS" , Robin Murphy , Linux Doc Mailing List , Linux Kernel Mailing List , Linux Media Mailing List Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-doc@vger.kernel.org On Wed, Oct 7, 2020 at 8:21 AM Christoph Hellwig wrote: > > On Tue, Oct 06, 2020 at 10:56:04PM +0200, Tomasz Figa wrote: > > > Yes. And make sure the API isn't implemented when VIVT caches are > > > used, but that isn't really different from the current interface. > > > > Okay, thanks. Let's see if we can make necessary changes to the videobuf2. > > > > +Sergey Senozhatsky for awareness too. > > I can defer the changes a bit to see if you'd really much prefer > the former interface. I think for now the most important thing is > that it works properly for the potential users, and the prime one is > videobuf2 for now. drm also seems like a big potential users, but I > had a really hard time getting the developers to engage in API > development. My initial feeling is that it should work, but we'll give you a definitive answer once we prototype it. :) We might actually give it a try in the USB HCD subsystem as well, to implement usb_alloc_noncoherent(), as an optimization for drivers which have to perform multiple random accesses to the URB buffers. I think you might recall discussing this by the way of the pwc and uvcvideo camera drivers. Best regards, Tomasz