Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752002AbdHEP56 (ORCPT ); Sat, 5 Aug 2017 11:57:58 -0400 Received: from vern.gendns.com ([206.190.152.46]:55516 "EHLO vern.gendns.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751226AbdHEP54 (ORCPT ); Sat, 5 Aug 2017 11:57:56 -0400 Subject: Re: [PATCH v5] drm/fb-helper: pass physical dimensions to fbdev To: Laurent Pinchart , dri-devel@lists.freedesktop.org Cc: linux-kernel@vger.kernel.org, Daniel Vetter References: <1501863924-7154-1-git-send-email-david@lechnology.com> <5131811.ZCEmYft6Yc@avalon> From: David Lechner Message-ID: <3ac80a0e-707c-6bf9-4e19-d3a455303ff4@lechnology.com> Date: Sat, 5 Aug 2017 10:57:50 -0500 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.2.1 MIME-Version: 1.0 In-Reply-To: <5131811.ZCEmYft6Yc@avalon> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-AntiAbuse: This header was added to track abuse, please include it with any abuse report X-AntiAbuse: Primary Hostname - vern.gendns.com X-AntiAbuse: Original Domain - vger.kernel.org X-AntiAbuse: Originator/Caller UID/GID - [47 12] / [47 12] X-AntiAbuse: Sender Address Domain - lechnology.com X-Get-Message-Sender-Via: vern.gendns.com: authenticated_id: davidmain+lechnology.com/only user confirmed/virtual account not confirmed X-Authenticated-Sender: vern.gendns.com: davidmain@lechnology.com X-Source: X-Source-Args: X-Source-Dir: Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 865 Lines: 22 On 08/04/2017 04:53 PM, Laurent Pinchart wrote: > Hi David, > > Thank you for the patch. > > On Friday 04 Aug 2017 11:25:24 David Lechner wrote: >> The fbdev subsystem has a place for physical dimensions (width and height >> in mm) that is readable by userspace. Since DRM also knows these >> dimensions, pass this information to the fbdev device. > > I'm curious, what's your use case for this ? What userspace software do you > use that is still based on fbdev and needs screen dimensions ? I have dug up an old graphics library called GRX[1] and modernized it[2]. So, I am using the screen dimensions to make it DPI-aware so that the font on my 2.4" screen looks the same size as my 2.8" screen when both are 320x240 pixels. Until this year, all of the displays I have only have fbdev drivers. [1]: http://grx.gnu.de [2]: https://github.com/ev3dev/grx