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[209.132.180.67]) by mx.google.com with ESMTP id v186si2075224pfb.284.2018.02.23.09.05.26; Fri, 23 Feb 2018 09:05:42 -0800 (PST) Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67; Authentication-Results: mx.google.com; dkim=pass header.i=@chromium.org header.s=google header.b=BbLkFo3u; spf=pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=chromium.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751460AbeBWREg (ORCPT + 99 others); Fri, 23 Feb 2018 12:04:36 -0500 Received: from mail-yb0-f195.google.com ([209.85.213.195]:36562 "EHLO mail-yb0-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751447AbeBWREe (ORCPT ); Fri, 23 Feb 2018 12:04:34 -0500 Received: by mail-yb0-f195.google.com with SMTP id e135-v6so3114258ybb.3 for ; Fri, 23 Feb 2018 09:04:34 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=chromium.org; s=google; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:content-transfer-encoding:in-reply-to :user-agent; bh=gMFoUgWAh+uRZkBdpXrDSBqciE16JvpAT+BcXN3E94s=; b=BbLkFo3uFjShcnmxk82C7i51GstvZzzgJm87zs+uEo75Gjh4YZjU/zHMqscvd+i80j yv14Ezk9phOKp3VCgbDaKSLI5Shkihw8vr8uRVfVw4GbSd5tpo86T12ptLMyTxcI5V8h WKnmZStJcZAmhtlv8QXkXwWsnl2QIQhx16eUc= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:content-transfer-encoding :in-reply-to:user-agent; bh=gMFoUgWAh+uRZkBdpXrDSBqciE16JvpAT+BcXN3E94s=; b=OCFapaxRM9SzzItU9f5gnXc37wJ6OBEroVsw8iwBM8ENVP7dx1SP6mDxe8D18CvBKv GcTL88BAqvcgNsbl3ROXRGeSGwqXyiYTmn81GNpbvZVCX6AnrtV0eWl5feUH9Bm1h9tK pp3C2RIEy2/G1FcqJOgz8F2UF8nbIq5PxKQ522ux4PIKgNKX045wKi8DsroHIMjF1eqv jPJWu8v9WmEsQWHEZV3D6WvPL0C9dQvDd54v8yLDQjP/g5vyTwrtV3fPOjtM4WFgkRmm gIYYRrydDXFXMstnH7tYh5AH7dRgekm5T1tCkRwn9w2Zmh0GHRnId3jrPUdLDKC1xXFf V+bA== X-Gm-Message-State: APf1xPCqp7vTolUXjnqO92Z6u0smCaYFn/ixCEhsNKHv/L3L6pGjhT2f hdY7X972NN/7HI5rPp+ctXIurw== X-Received: by 2002:a25:8688:: with SMTP id z8-v6mr1517644ybk.265.1519405473924; Fri, 23 Feb 2018 09:04:33 -0800 (PST) Received: from localhost ([2620:0:1013:11:d3af:69ac:1964:28e8]) by smtp.gmail.com with ESMTPSA id f81sm1069785ywc.92.2018.02.23.09.04.32 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Fri, 23 Feb 2018 09:04:32 -0800 (PST) Date: Fri, 23 Feb 2018 12:04:32 -0500 From: Sean Paul To: Liviu Dudau Cc: Sean Paul , Rob Clark , dri-devel , freedreno , linux-arm-msm , Brian Starkey , Mihail Atanassov , Gustavo Padovan , Maarten Lankhorst , David Airlie , Jonathan Corbet , linux-doc@vger.kernel.org, Linux Kernel Mailing List , daniel.vetter@ffwll.ch Subject: Re: [RFC 1/4] drm: Add writeback connector type Message-ID: <20180223170432.GP223881@art_vandelay> References: <20180223131758.18362-1-robdclark@gmail.com> <20180223131758.18362-2-robdclark@gmail.com> <20180223155935.GJ223881@art_vandelay> <20180223164329.GO223881@art_vandelay> <20180223164858.GY9111@e110455-lin.cambridge.arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20180223164858.GY9111@e110455-lin.cambridge.arm.com> User-Agent: Mutt/1.9.2 (2017-12-15) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Feb 23, 2018 at 04:48:58PM +0000, Liviu Dudau wrote: > On Fri, Feb 23, 2018 at 11:43:29AM -0500, Sean Paul wrote: > > On Fri, Feb 23, 2018 at 11:25:11AM -0500, Rob Clark wrote: > > > On Fri, Feb 23, 2018 at 10:59 AM, Sean Paul wrote: > > > > > > > > Have we considered hiding writeback behind a client cap instead? > > > > > > It is kinda *almost* unneeded, since the connector reports itself as > > > disconnected. > > > > > > I'm not sure what the reason was to drop the cap, but I think it would > > > be better to have a cap so WB connectors don't show up in, for ex, > > > xrandr > > > > Yeah, the disconnected hack is kind of gross, IMO. I hate to introduce churn in > > the patch series given that it was initially introduced with the client cap. > > Haha, that's the reverse of Daniel's position: > > https://lists.freedesktop.org/archives/dri-devel/2016-October/120519.html Yeah, it happens :(. I don't think it's a dealbreaker either way, it just seems awkward to expose a connector which is "disconnected", but available for use. I don't think we have any other connectors which are supposed to be used in this state. > > > > > There are also cases where we might want to make writeback unavailable, such as > > when content protection is enabled. In those cases, it's conceivable that we > > might want to use disconnected as a signal to u/s. I suppose we could also just > > fail the check, so most of this is just academic. > > Not sure what other hardware out there does, but on Mali DP's case you > would be outputing the protected content by putting the display > processor in secure mode, which automatically disables writeback for us. > Or to put in another way, you don't need a writeback framebuffer if you > are in non-secure mode as you can get access to the framebuffer used for > the plane anyway. Yeah, I was mostly thinking about the case where you might have HDCP enabled on the HDMI connector and be able to slurp up the content via a writeback. However if the buffer is not secure in the first place, then it's already accessible in userspace so I don't think that writeback presents a new security hole. /me needs to get HDCP out of his head. Sean > > Best regards, > Liviu > > > > > Sean > > > > > > > > > > BR, > > > -R > > > > -- > > Sean Paul, Software Engineer, Google / Chromium OS > > -- > ==================== > | I would like to | > | fix the world, | > | but they're not | > | giving me the | > \ source code! / > --------------- > ¯\_(ツ)_/¯ -- Sean Paul, Software Engineer, Google / Chromium OS