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[209.132.180.67]) by mx.google.com with ESMTP id m11si5162110plt.26.2019.01.07.02.14.57; Mon, 07 Jan 2019 02:15:12 -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=@kroah.com header.s=fm2 header.b=VBlinL9R; dkim=pass header.i=@messagingengine.com header.s=fm1 header.b=n8IIP0OJ; 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 Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726758AbfAGKNA (ORCPT + 99 others); Mon, 7 Jan 2019 05:13:00 -0500 Received: from wout2-smtp.messagingengine.com ([64.147.123.25]:41043 "EHLO wout2-smtp.messagingengine.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725550AbfAGKNA (ORCPT ); Mon, 7 Jan 2019 05:13:00 -0500 Received: from compute6.internal (compute6.nyi.internal [10.202.2.46]) by mailout.west.internal (Postfix) with ESMTP id 598731431; Mon, 7 Jan 2019 05:12:58 -0500 (EST) Received: from mailfrontend1 ([10.202.2.162]) by compute6.internal (MEProxy); Mon, 07 Jan 2019 05:12:59 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kroah.com; h= date:from:to:cc:subject:message-id:references:mime-version :content-type:in-reply-to; s=fm2; bh=bUr2uSJslzFSQjpLPjUpt/KLbov Iy3XFjirj3IH6TzI=; b=VBlinL9RFieXN8sK11N9ePEnuw4EKVh16UggoN3h9iV rmaY9yEdWmdCynWMIAMJ13+IFeor23dsLGbG4us0AGQIef1cib+f9DZc+6qZiQNQ QYXwxyDgV8CicGKomLS1Sq4/xX22b3tCm6IVqlucJj0NAUNOEM8L64Z+t2+O1ToU Hk21ZAxTfF5w/3eVEul1J1Hs2WcNiVszAFJ18DyEZ+XQv1kWc5vDnG9N1EU1ycV+ rJ70v2MQOI77dHPEMaxUTtybCrWzqhMLXNwj4qvJ9Spc22mB1qSvZqcEynrxaBbj MgmDeyzF7ifoiHGsfKmSYqlZ+Cw+NZ0nciWptGi9TsQ== DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d= messagingengine.com; h=cc:content-type:date:from:in-reply-to :message-id:mime-version:references:subject:to:x-me-proxy :x-me-proxy:x-me-sender:x-me-sender:x-sasl-enc; s=fm1; bh=bUr2uS JslzFSQjpLPjUpt/KLbovIy3XFjirj3IH6TzI=; b=n8IIP0OJXrRp5YWeOcNFW1 4JpqnyGfCIsnHiwQZaWkB92itUpIeJYPYuzDJD6gSGz7K30PsO4aD2+KfgLmnwBY euFRXnHU1mMacW81c/ghe4zfZ//VheBKm8/3rjQv+m+4MqZPKbShR4ik6O080XBB Hei6QE+WxUr73jrv4u9W+8zQscLoGhjCS6eTypBKrHgLQLcBtP6nVAs0V2qTUf7r ovAdDmHcbV6K+2mzKpWOgr0tG6SB4qMf1f9df6aqGWqgsMWsm4lEzqXgwaopyTs7 JMf20sB2w9ouNGwNUiQNPVPeQq8VPuHCBIrjkd8qeNXlgFTHGCDAI/ob8lNI9hRg == X-ME-Sender: X-ME-Proxy-Cause: gggruggvucftvghtrhhoucdtuddrgedtledrvdejgdduudculddtuddrgedtkedrtddtmd cutefuodetggdotefrodftvfcurfhrohhfihhlvgemucfhrghsthforghilhdpqfhuthen uceurghilhhouhhtmecufedttdenucesvcftvggtihhpihgvnhhtshculddquddttddmne cujfgurhepfffhvffukfhfgggtuggjfgesthdtredttdervdenucfhrhhomhepifhrvghg ucfmjfcuoehgrhgvgheskhhrohgrhhdrtghomheqnecuffhomhgrihhnpehsohhurhgtvg hfohhrghgvrdhnvghtnecukfhppeekfedrkeeirdekledruddtjeenucfrrghrrghmpehm rghilhhfrhhomhepghhrvghgsehkrhhorghhrdgtohhmnecuvehluhhsthgvrhfuihiivg eptd X-ME-Proxy: Received: from localhost (5356596b.cm-6-7b.dynamic.ziggo.nl [83.86.89.107]) by mail.messagingengine.com (Postfix) with ESMTPA id 836CAE4662; Mon, 7 Jan 2019 05:12:56 -0500 (EST) Date: Mon, 7 Jan 2019 11:12:55 +0100 From: Greg KH To: Ivan Mironov Cc: Daniel Vetter , dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, Maarten Lankhorst , Maxime Ripard , Sean Paul , David Airlie , saahriktu , Eugeniy Paltsev Subject: Re: [PATCH v1 2/2] drm/fb-helper: Ignore the value of fb_var_screeninfo.pixclock Message-ID: <20190107101255.GA2364@kroah.com> References: <20181227231308.16904-1-mironov.ivan@gmail.com> <20181227231308.16904-3-mironov.ivan@gmail.com> <20181228120652.GR9058@dvetter-linux.ger.corp.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.11.1 (2018-12-01) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, Jan 05, 2019 at 09:21:21PM +0500, Ivan Mironov wrote: > On Fri, 2018-12-28 at 13:06 +0100, Daniel Vetter wrote: > > On Fri, Dec 28, 2018 at 04:13:08AM +0500, Ivan Mironov wrote: > > > Strict requirement of pixclock to be zero breaks support of SDL 1.2 > > > which contains hardcoded table of supported video modes with non-zero > > > pixclock values[1]. > > > > > > To better understand which pixclock values are considered valid and how > > > driver should handle these values, I briefly examined few existing fbdev > > > drivers and documentation in Documentation/fb/. And it looks like there > > > are no strict rules on that and actual behaviour varies: > > > > > > * some drivers treat (pixclock == 0) as "use defaults" (uvesafb.c); > > > * some treat (pixclock == 0) as invalid value which leads to > > > -EINVAL (clps711x-fb.c); > > > * some pass converted pixclock value to hardware (uvesafb.c); > > > * some are trying to find nearest value from predefined table > > > (vga16fb.c, video_gx.c). > > > > > > Given this, I believe that it should be safe to just ignore this value if > > > changing is not supported. It seems that any portable fbdev application > > > which was not written only for one specific device working under one > > > specific kernel version should not rely on any particular behaviour of > > > pixclock anyway. > > > > > > However, while enabling SDL1 applications to work out of the box when > > > there is no /etc/fb.modes with valid settings, this change affects the > > > video mode choosing logic in SDL. Depending on current screen > > > resolution, contents of /etc/fb.modes and resolution requested by > > > application, this may lead to user-visible difference (not always): > > > image will be displayed in a right way, but it will be aligned to the > > > left instead of center. There is no "right behaviour" here as well, as > > > emulated fbdev, opposing to old fbdev drivers, simply ignores any > > > requsts of video mode changes with resolutions smaller than current. > > > > > > Feel free to NAK this patch if you think that it causes breakage of > > > user-space =). > > > > It's a regression, we don't nack regression fixes :-) > > > > > The easiest way to reproduce this problem is to install sdl-sopwith[2], > > > remove /etc/fb.modes file if it exists, and then try to run sopwith > > > from console without X. At least in Fedora 29, sopwith may be simply > > > installed from standard repositories. > > > > > > [1] SDL 1.2.15 source code, src/video/fbcon/SDL_fbvideo.c, vesa_timings > > > [2] http://sdl-sopwith.sourceforge.net/ > > > > > > Signed-off-by: Ivan Mironov > > > > I thought this is also a regression fix, so also needs Fixes: and cc: > > stable? > > -Daniel > > This particular patch fixes a bug that existed for 10 years unnoticed. > Are "Fixes:" and "Cc: stable" really required? If you want it backported into a stable kernel release, then yes, they are needed :) thanks, greg k-h