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([240b:10:c9a0:ca00:5192:32ad:e5be:23cd]) by smtp.gmail.com with ESMTPSA id x20sm16719962pfh.112.2021.06.21.21.03.00 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 21 Jun 2021 21:03:03 -0700 (PDT) Subject: Re: [PATH 0/4] [RFC] Support virtual DRM To: Thomas Zimmermann Cc: Maarten Lankhorst , Maxime Ripard , David Airlie , Daniel Vetter , Laurent Pinchart , Kieran Bingham , dri-devel@lists.freedesktop.org, linux-renesas-soc@vger.kernel.org, linux-kernel@vger.kernel.org, devicetree@vger.kernel.org, linux-doc@vger.kernel.org, Damian Hobson-Garcia , Takanari Hayama References: <20210621062742.26073-1-etom@igel.co.jp> <9853d0a9-6053-db64-9c79-40b7e0689eec@suse.de> From: Esaki Tomohito Message-ID: <85593f2f-5aa9-6023-ecba-c5275a468b71@igel.co.jp> Date: Tue, 22 Jun 2021 13:02:59 +0900 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.11.0 MIME-Version: 1.0 In-Reply-To: <9853d0a9-6053-db64-9c79-40b7e0689eec@suse.de> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, Thomas Thank you for reply. On 2021/06/21 16:10, Thomas Zimmermann wrote: > Hi > > Am 21.06.21 um 08:27 schrieb Tomohito Esaki: >> Virtual DRM splits the overlay planes of a display controller into >> multiple >> virtual devices to allow each plane to be accessed by each process. >> >> This makes it possible to overlay images output from multiple >> processes on a >> display. For example, one process displays the camera image without >> compositor >> while another process overlays the UI. > > I briefly looked over your patches. I didn't understand how this is > different to the functionality of a compositor? Shouldn't this be solved > in userspace? I think when latency is important (e.g., AR, VR, for displaying camera images in IVI systems), there may be use cases where the compositor cannot be used. Normally, when the image is passed through the compositor, it is displayed after 2 VSYNC at most, because the compositor combines the image with VSYNC synchronization. On the other hand, if we use vDRM, the image will be displayed at the next VSYNC, so it will be displayed after 1 VSYNC at most. Also, since the compositor is a single point of failure, we may not want to make it dependent on it. Best regards Tomohito Esaki 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=-5.1 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A, 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 0BCD6C2B9F4 for ; Tue, 22 Jun 2021 04:03:08 +0000 (UTC) Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 9839F611CE for ; Tue, 22 Jun 2021 04:03:07 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 9839F611CE Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=igel.co.jp Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=dri-devel-bounces@lists.freedesktop.org Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id E61AD6E10C; Tue, 22 Jun 2021 04:03:06 +0000 (UTC) Received: from mail-pg1-x532.google.com (mail-pg1-x532.google.com [IPv6:2607:f8b0:4864:20::532]) by gabe.freedesktop.org (Postfix) with ESMTPS id EEC4B6E10C for ; Tue, 22 Jun 2021 04:03:04 +0000 (UTC) Received: by mail-pg1-x532.google.com with SMTP id t13so4183571pgu.11 for ; Mon, 21 Jun 2021 21:03:04 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=igel-co-jp.20150623.gappssmtp.com; s=20150623; h=subject:to:cc:references:from:message-id:date:user-agent :mime-version:in-reply-to:content-language:content-transfer-encoding; bh=LCU0yJ9k9lkuiH4BXOzJ8l7LNMuqUv70T9bND/kl8Tc=; b=2IRIENBoxAqdiYLU9/rOfm8louoM9XJGUrNr4bDU2GLRrypkgatHI8hkFkeTbyRLbG GT8Nb16qpHMXS+sHckMEspeY/jRj+8I0oJ+xQDQY5gwUOxmGciFsHz3INa2KoN5DLghx 887kkP0AQGfaUA7l3YlEg0I4iq//vGSCtuiTAZpnAOyBu3j7nNkuE0F3ZHhE1m/ZRszu YsdAHz3Cv5q0n9L2hHkLVzqTOCsD3GXOzpOyjxV34rQc12+D55Tva5Rpcj3R7b7qcXn5 Y1pc9qLwY7Lt6RKJIVyCzGTtxHovj1ReEzkFjNi5lnJ9NA39zpgHg7q+s9topcsVBFe9 rOjA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:cc:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=LCU0yJ9k9lkuiH4BXOzJ8l7LNMuqUv70T9bND/kl8Tc=; b=bp5NeAxoIYSlJVptw2jlvh176D8704PtRD5CX9lD2C0zEyUP2ALjxn+zSGsupvxXP2 1A+QGiECGcAq9ixT4aR6GdKONMbBEGg8gAryH6lcF1GJBiEnHRS+qrg/F2KalJNEja8W n+mRujH1XZdbDGT06FRtj4oiNYmfZmTdeH/BJGfqfu3KnBd1k5pEeWtbxWCMcZ9+ybxG 2LuLsLFi6BRu9hSPx01zLc8m5oMnj3CyRJQOyVCPW9nsd1DPmamq6gPrF2B/p84eWIik BUXUKQ22wKAg/n6xdBj1ns4DpBgb2hN8E0sQAGPjrEgPudjO3TWdmLblP59Y/2IAgRIC zcMQ== X-Gm-Message-State: AOAM533WWhj/UrCQQDLTLwgYh/1/dPmQyA4wSI9nhSOtSZ5xxZR7edxl WqSpLRgTpDLTZ1G3kJbd7qQ6jg== X-Google-Smtp-Source: ABdhPJyKj/BVU5tSTB/YxCiCQydfHrVE81rBbCx40oGNuZ57J9fDCnwKUCuoM0Jyxaso51VahEdMJw== X-Received: by 2002:a05:6a00:1515:b029:2f1:d29:2a44 with SMTP id q21-20020a056a001515b02902f10d292a44mr1605587pfu.51.1624334584489; Mon, 21 Jun 2021 21:03:04 -0700 (PDT) Received: from ?IPv6:240b:10:c9a0:ca00:5192:32ad:e5be:23cd? ([240b:10:c9a0:ca00:5192:32ad:e5be:23cd]) by smtp.gmail.com with ESMTPSA id x20sm16719962pfh.112.2021.06.21.21.03.00 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 21 Jun 2021 21:03:03 -0700 (PDT) Subject: Re: [PATH 0/4] [RFC] Support virtual DRM To: Thomas Zimmermann References: <20210621062742.26073-1-etom@igel.co.jp> <9853d0a9-6053-db64-9c79-40b7e0689eec@suse.de> From: Esaki Tomohito Message-ID: <85593f2f-5aa9-6023-ecba-c5275a468b71@igel.co.jp> Date: Tue, 22 Jun 2021 13:02:59 +0900 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.11.0 MIME-Version: 1.0 In-Reply-To: <9853d0a9-6053-db64-9c79-40b7e0689eec@suse.de> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: devicetree@vger.kernel.org, Takanari Hayama , linux-doc@vger.kernel.org, David Airlie , dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, linux-renesas-soc@vger.kernel.org, Kieran Bingham , Laurent Pinchart , Damian Hobson-Garcia Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" Hi, Thomas Thank you for reply. On 2021/06/21 16:10, Thomas Zimmermann wrote: > Hi > > Am 21.06.21 um 08:27 schrieb Tomohito Esaki: >> Virtual DRM splits the overlay planes of a display controller into >> multiple >> virtual devices to allow each plane to be accessed by each process. >> >> This makes it possible to overlay images output from multiple >> processes on a >> display. For example, one process displays the camera image without >> compositor >> while another process overlays the UI. > > I briefly looked over your patches. I didn't understand how this is > different to the functionality of a compositor? Shouldn't this be solved > in userspace? I think when latency is important (e.g., AR, VR, for displaying camera images in IVI systems), there may be use cases where the compositor cannot be used. Normally, when the image is passed through the compositor, it is displayed after 2 VSYNC at most, because the compositor combines the image with VSYNC synchronization. On the other hand, if we use vDRM, the image will be displayed at the next VSYNC, so it will be displayed after 1 VSYNC at most. Also, since the compositor is a single point of failure, we may not want to make it dependent on it. Best regards Tomohito Esaki