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[209.85.128.47]) by smtp.gmail.com with ESMTPSA id k8sm317514ejz.60.2020.09.08.14.58.33 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 08 Sep 2020 14:58:33 -0700 (PDT) Received: by mail-wm1-f47.google.com with SMTP id b79so432347wmb.4 for ; Tue, 08 Sep 2020 14:58:33 -0700 (PDT) X-Received: by 2002:a1c:c20a:: with SMTP id s10mr433507wmf.55.1599602313215; Tue, 08 Sep 2020 14:58:33 -0700 (PDT) MIME-Version: 1.0 References: <20200819065555.1802761-1-hch@lst.de> <20200819065555.1802761-6-hch@lst.de> <20200819135454.GA17098@lst.de> <20200820044347.GA4533@lst.de> <20200820052004.GA5305@lst.de> <20200820165407.GD12693@lst.de> <20200901110617.GA13232@lst.de> In-Reply-To: From: Tomasz Figa Date: Tue, 8 Sep 2020 23:58:22 +0200 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH 05/28] media/v4l2: remove V4L2-FLAG-MEMORY-NON-CONSISTENT To: Hans Verkuil , Mauro Carvalho Chehab Cc: Christoph Hellwig , Linux Media Mailing List , Linux Kernel Mailing List , Sergey Senozhatsky Content-Type: text/plain; charset="UTF-8" Sender: linux-media-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-media@vger.kernel.org Hi Hans, Mauro, On Tue, Sep 1, 2020 at 5:02 PM Tomasz Figa wrote: > > On Tue, Sep 1, 2020 at 1:06 PM Christoph Hellwig wrote: > > > > On Thu, Aug 20, 2020 at 07:33:48PM +0200, Tomasz Figa wrote: > > > > It wasn't meant to be too insulting, but I found this out when trying > > > > to figure out how to just disable it. But it also ends up using > > > > the actual dma attr flags for it's own consistency checks, so just > > > > not setting the flag did not turn out to work that easily. > > > > > > > > > > Yes, sadly the videobuf2 ended up becoming quite counterintuitive > > > after growing for the long years and that is reflected in the design > > > of this feature as well. I think we need to do something about it. > > > > So I'm about to respin the series and wonder how we should proceed. > > I've failed to come up with a clean patch to keep the flag and make > > it a no-op. Can you or your team give it a spin? > > > > Okay, I'll take a look. > > > Also I wonder if the flag should be renamed from NON_CONSISTENT > > to NON_COHERENT - the consistent thing is a weird wart from the times > > the old PCI DMA API that is mostly gone now. > > It originated from the DMA_ATTR_NON_CONSISTENT flag, but agreed that > NON_COHERENT would be more consistent (pun not intended) with the rest > of the DMA API given the removal of that flag. Let me see if we can > still change it. Given the above, we would like to make changes that affect the UAPI. Would you still be able to revert this series? Best regards, Tomasz