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=-4.2 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_2 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 9361EC48BE5 for ; Tue, 22 Jun 2021 07:58:04 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 777136128C for ; Tue, 22 Jun 2021 07:58:04 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229789AbhFVIAS (ORCPT ); Tue, 22 Jun 2021 04:00:18 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:39836 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230182AbhFVIAS (ORCPT ); Tue, 22 Jun 2021 04:00:18 -0400 Received: from mail-lj1-x22b.google.com (mail-lj1-x22b.google.com [IPv6:2a00:1450:4864:20::22b]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 78A60C061574; Tue, 22 Jun 2021 00:58:02 -0700 (PDT) Received: by mail-lj1-x22b.google.com with SMTP id u11so17896031ljh.2; Tue, 22 Jun 2021 00:58:02 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=date:from:to:cc:subject:message-id:in-reply-to:references :mime-version; bh=u8GLty3tOXL1FdPiA/Irm6Dck8CZ9gdJPuMIDM8NO+g=; b=d7iFiJQ73FVsnECWrp/feRn6JQJRkwTvGErWNpA2d1IoBAezEyvzoYNpLC6ucfTCBu I6loo0sLSeysO9MpFd99ZcYndA3NYU2TqdipUr9scVYTOPsyA3KxxScRq0Wp9PmFfKrb cb3uDYYRjpauTOuB4ksrAX153C1jryvrvgR2b9PghLdwh5vqtUGgoKCrDZfBcOyYVDds qRj/rmJ4z44Qtx9Bxi9g0Z5z6i/dX+Gac9i5Ixc0Xw9u/cbJulJJ4CztAqPbODcH+bA7 PA7MxdYWbvdXTBcvRay2UzNJNN6YUS/vqWBUHm1kYuccBeTrSMoLBHIy0O+IKNGN7CcJ jgXQ== 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:in-reply-to :references:mime-version; bh=u8GLty3tOXL1FdPiA/Irm6Dck8CZ9gdJPuMIDM8NO+g=; b=MVzUS//3Yd0KA9I28lNVlVwXCpjqlrQDSPDzgGKxlhzsLPzEWU9WKbn0vPo9EGv5NG ERrOcW3l50NiTjJmWZtCbEDR5cnGxjbH54OdipKW5SaurINgkLtCTcJKOh0bZIn4YTic oT5JIQjyaYwIKUsB9kcIlfmCwD7+Y7X6mw0QZE5ZJZBHr2g0qCEjmJXozR+JGMiCideY cP3ue3KH7JdyBtKZ+YyX7qMEHrR1aqMjZeK+M5L77rhWi3oiKZbSv00HfGELNFV2Qy3K 6mZ8OKTowXrNam2wkAKjCDquwBjOmqxbv7bFtA6yS2DirTjt+nIz3Y+72SSgieL5WK/X JnLQ== X-Gm-Message-State: AOAM531FH/pw778RW+RI0N/tTjdfBNiw7pKCJEl9J1X/HrDj5QgWnysB ufUZtMyvxJG7uUunSUCpSYI= X-Google-Smtp-Source: ABdhPJwpT7cg8PaaS+cBElIDaTgWonJwsRlSSCUx8dbqTLht5p2QNMd+5QPV5OR6nXmvC+gWz/IOsA== X-Received: by 2002:a2e:90ca:: with SMTP id o10mr2043374ljg.299.1624348680814; Tue, 22 Jun 2021 00:58:00 -0700 (PDT) Received: from eldfell ([194.136.85.206]) by smtp.gmail.com with ESMTPSA id u2sm2521546ljg.134.2021.06.22.00.58.00 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 22 Jun 2021 00:58:00 -0700 (PDT) Date: Tue, 22 Jun 2021 10:57:57 +0300 From: Pekka Paalanen To: Esaki Tomohito Cc: Thomas Zimmermann , 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 Subject: Re: [PATH 0/4] [RFC] Support virtual DRM Message-ID: <20210622105757.2b9dec32@eldfell> In-Reply-To: <85593f2f-5aa9-6023-ecba-c5275a468b71@igel.co.jp> References: <20210621062742.26073-1-etom@igel.co.jp> <9853d0a9-6053-db64-9c79-40b7e0689eec@suse.de> <85593f2f-5aa9-6023-ecba-c5275a468b71@igel.co.jp> X-Mailer: Claws Mail 3.17.3 (GTK+ 2.24.32; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; boundary="Sig_/k_Ny_BZtmz_EeVKX1+Wmizg"; protocol="application/pgp-signature" Precedence: bulk List-ID: X-Mailing-List: devicetree@vger.kernel.org --Sig_/k_Ny_BZtmz_EeVKX1+Wmizg Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: quoted-printable On Tue, 22 Jun 2021 13:02:59 +0900 Esaki Tomohito wrote: > Hi, Thomas > Thank you for reply. >=20 > On 2021/06/21 16:10, Thomas Zimmermann wrote: > > Hi > >=20 > > Am 21.06.21 um 08:27 schrieb Tomohito Esaki: =20 > >> 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. =20 > >=20 > > 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? =20 >=20 > 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. Hi, > 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. This is not a universal fact. You can write a Wayland compositor that consistently reaches app-to-screen latency of less than one monitor refresh cycle, while also using KMS planes. I believe Weston succeeds in this already if you write the Wayland application accordingly. 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