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=-3.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED 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 63DB2C433DB for ; Thu, 7 Jan 2021 08:14:18 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 353B623137 for ; Thu, 7 Jan 2021 08:14:18 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726522AbhAGIOC (ORCPT ); Thu, 7 Jan 2021 03:14:02 -0500 Received: from mail-oi1-f177.google.com ([209.85.167.177]:44720 "EHLO mail-oi1-f177.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726171AbhAGIOC (ORCPT ); Thu, 7 Jan 2021 03:14:02 -0500 Received: by mail-oi1-f177.google.com with SMTP id d189so6490131oig.11; Thu, 07 Jan 2021 00:13:46 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=2sNU56Ph9zOh5AccBeHHxNWeCtZj6RXCAKwJxVBMKmE=; b=UunNUgONTNSLs9KQH9szadf8eYTaPHc7X+IR67UsD/7/utczvqG7173tay/KazIZoN jtMaFekKPASOb81DdC3hZbakxN3q6LNcAU7jA9RrOzNi6IqHWE1j9lJEIAVmkUl3xR9a Mxcy4yvhf2RDay9H0l3uMro2+GBfWoS6dxW9PcaMTTiJiA7PD9ZbHsiLKtMNrbVhRRuI NGED7BfRVLws1Iaing6f/r2zJCI3RnvcN7PICWhOBaOCmEItx2+e4CbQVrNMa7s4Yfyz 7nAzfo66o9Q8a9gImc1FtMFhUmal8ZID9OrLVCPBj9ssxcs7lD+7JlBWBgWUF9gSp++l 5fog== X-Gm-Message-State: AOAM531XxIv3jd2jkNv7F6FFWHrCdmtOhwBunGG69AoiefRKv2Xr2vs5 wu6CTD+SF3ZSZNrA/FuBKRTXnHZ4S2YBhoHY8kTXD2AhJOw= X-Google-Smtp-Source: ABdhPJwrnQjPXBYzM2SyYW1CfGTO1vgkI2yKYDdyKTlIhuNFDs8Idq4cEQdtVae6Q4iQGMePy4f/z4WxW1zGTn3wWGI= X-Received: by 2002:aca:3cc5:: with SMTP id j188mr684519oia.54.1610007201402; Thu, 07 Jan 2021 00:13:21 -0800 (PST) MIME-Version: 1.0 References: <20210104155708.800470590@linuxfoundation.org> <20210104155710.187945647@linuxfoundation.org> In-Reply-To: <20210104155710.187945647@linuxfoundation.org> From: Geert Uytterhoeven Date: Thu, 7 Jan 2021 09:13:10 +0100 Message-ID: Subject: Re: [PATCH 5.10 28/63] fbcon: Disable accelerated scrolling To: Greg Kroah-Hartman Cc: Linux Kernel Mailing List , stable , Tomi Valkeinen , Thomas Zimmermann , Sam Ravnborg , Jiri Slaby , Bartlomiej Zolnierkiewicz , Linus Torvalds , Ben Skeggs , Nouveau Dev , Daniel Vetter , "Gustavo A. R. Silva" , Tetsuo Handa , Peilin Ye , George Kennedy , Nathan Chancellor , Peter Rosin , Daniel Vetter Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Jan 4, 2021 at 5:58 PM Greg Kroah-Hartman wrote: > From: Daniel Vetter > > commit 39aead8373b3c20bb5965c024dfb51a94e526151 upstream. > > So ever since syzbot discovered fbcon, we have solid proof that it's > full of bugs. And often the solution is to just delete code and remove > features, e.g. 50145474f6ef ("fbcon: remove soft scrollback code"). > > Now the problem is that most modern-ish drivers really only treat > fbcon as an dumb kernel console until userspace takes over, and Oops > printer for some emergencies. Looking at drm drivers and the basic > vesa/efi fbdev drivers shows that only 3 drivers support any kind of > acceleration: > > - nouveau, seems to be enabled by default > - omapdrm, when a DMM remapper exists using remapper rewriting for > y/xpanning > - gma500, but that is getting deleted now for the GTT remapper trick, > and the accelerated copyarea never set the FBINFO_HWACCEL_COPYAREA > flag, so unused (and could be deleted already I think). > > No other driver supportes accelerated fbcon. And fbcon is the only Note that there are 32 more drivers using acceleration under drivers/video/fbdev/. Gr{oetje,eeting}s, Geert -- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org In personal conversations with technical people, I call myself a hacker. But when I'm talking to journalists I just say "programmer" or something like that. -- Linus Torvalds