From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754216AbdBNUFf (ORCPT ); Tue, 14 Feb 2017 15:05:35 -0500 Received: from mail-oi0-f65.google.com ([209.85.218.65]:33460 "EHLO mail-oi0-f65.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753971AbdBNUFY (ORCPT ); Tue, 14 Feb 2017 15:05:24 -0500 Date: Tue, 14 Feb 2017 21:05:20 +0100 From: Daniel Vetter To: Shuah Khan Cc: Jani Nikula , daniel.vetter@intel.com, seanpaul@chromium.org, airlied@linux.ie, linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org Subject: Re: [PATCH] drm: change connector disconnected debug message to an error Message-ID: <20170214200520.GB22762@dvetter-linux.ger.corp.intel.com> Mail-Followup-To: Shuah Khan , Jani Nikula , daniel.vetter@intel.com, seanpaul@chromium.org, airlied@linux.ie, linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org References: <20170202025904.25810-1-shuahkh@osg.samsung.com> <874m0d0z7o.fsf@intel.com> <9d3783d1-b8f8-bd82-3141-1897980197da@osg.samsung.com> <20170203080622.j2fms2hf3pmz7uqb@phenom.ffwll.local> <3608e354-806e-6e43-2392-2c1e31e882a3@osg.samsung.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <3608e354-806e-6e43-2392-2c1e31e882a3@osg.samsung.com> X-Operating-System: Linux dvetter-linux.ger.corp.intel.com 4.8.15-200.fc24.x86_64 User-Agent: Mutt/1.7.1 (2016-10-04) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Feb 10, 2017 at 09:29:07AM -0700, Shuah Khan wrote: > On 02/03/2017 01:06 AM, Daniel Vetter wrote: > > On Thu, Feb 02, 2017 at 10:25:44AM -0700, Shuah Khan wrote: > >> On 02/02/2017 01:32 AM, Jani Nikula wrote: > >>> On Thu, 02 Feb 2017, Shuah Khan wrote: > >>>> Change drm_helper_probe_single_connector_modes() to print an error to > >>>> report connector disconnected status instead of a debug message. > >>>> > >>>> When this condition occurs, application doesn't know the real error and > >>>> reports it as driver lacking support for mode setting. Change it to an > >>>> error to make it easier to debug. > >>> > >>> Please explain what makes this condition an error. Connectors get > >>> connected and disconnected, business as usual, why should this be an > >>> error? > >>> > >>> BR, > >>> Jani. > >> > >> Disconnecting connector itself isn't an error. When user-space tries > >> to access it, it would be useful to report the status that the connector > >> is disconnected. > >> > >> I use embedded system(s) that don't like it when HDMI is hot added or > >> removed. Also, because of return power, it is safer to disconnect HDMI > >> and then apply power to the board. It chased a few libdrm and user-space > >> dead ends before I enabled drm debug and was able to fix the real issue, > >> which is a disconnected cable. > >> > >> User-space prints rather confusing messages as it doesn't really know > >> the disconnected status as it isn't returned to it. > >> > >> I figured it might be a good idea to at least print a message and this can > >> be a notice or info instead of an error. I do think its is worth while in > >> some cases. > > > > This sounds like a very specific use-case you have here, and it can easily > > be supported by a small deamon in userspace (only on debug builds ofc) > > that tell you that someone unplugged the screen when it shouldn't have > > been. > > drm_helper_probe_single_connector_modes() finds the condition and doesn't > have a means to return it to the user-space. Erhm, we send out the uevent for this, and userspace can react. If that's not working, then we need to fix this bug, not add more uapi interfaces on top ... -Daniel > > Instead of error or debug message, would it be useful to add a trace event > to report status of connector to drm_helper_probe_single_connector_modes() > Trace could be triggered as needed and turned off. > > Please let me know what you think of this idea? If it sounds useful, I can > add it. > > > > > Because upstream runs also on non-embedded systems, where unplugging is > > normal, and we definitely don't want to spam dmesg. > > -Daniel > > > > thanks, > -- Shuah > > _______________________________________________ > dri-devel mailing list > dri-devel@lists.freedesktop.org > https://lists.freedesktop.org/mailman/listinfo/dri-devel -- Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch