From mboxrd@z Thu Jan  1 00:00:00 1970
From: Jani Nikula <jani.nikula@intel.com>
Subject: Re: [PATCH 1/2] drm/i915: add sanity checks for hsync
	and htotal
Date: Thu, 21 Jun 2012 10:33:12 +0300
Message-ID: <87zk7xw24n.fsf@intel.com>
References: <68e45eed497d3fef1ee9756f4648eb97b7fdd4aa.1340222977.git.jani.nikula@intel.com>
	<1340228186.14667.7.camel@atropine>
Mime-Version: 1.0
Content-Type: text/plain; charset="us-ascii"
Content-Transfer-Encoding: 7bit
Return-path: <intel-gfx-bounces+gcfxdi-intel-gfx=m.gmane.org@lists.freedesktop.org>
Received: from mga02.intel.com (mga02.intel.com [134.134.136.20])
	by gabe.freedesktop.org (Postfix) with ESMTP id 245F3A0ABD
	for <intel-gfx@lists.freedesktop.org>;
	Thu, 21 Jun 2012 00:30:42 -0700 (PDT)
In-Reply-To: <1340228186.14667.7.camel@atropine>
List-Unsubscribe: <http://lists.freedesktop.org/mailman/options/intel-gfx>,
	<mailto:intel-gfx-request@lists.freedesktop.org?subject=unsubscribe>
List-Archive: <http://lists.freedesktop.org/archives/intel-gfx>
List-Post: <mailto:intel-gfx@lists.freedesktop.org>
List-Help: <mailto:intel-gfx-request@lists.freedesktop.org?subject=help>
List-Subscribe: <http://lists.freedesktop.org/mailman/listinfo/intel-gfx>,
	<mailto:intel-gfx-request@lists.freedesktop.org?subject=subscribe>
Sender: intel-gfx-bounces+gcfxdi-intel-gfx=m.gmane.org@lists.freedesktop.org
Errors-To: intel-gfx-bounces+gcfxdi-intel-gfx=m.gmane.org@lists.freedesktop.org
To: Adam Jackson <ajax@redhat.com>
Cc: intel-gfx@lists.freedesktop.org
List-Id: intel-gfx@lists.freedesktop.org

On Thu, 21 Jun 2012, Adam Jackson <ajax@redhat.com> wrote:
> On Wed, 2012-06-20 at 23:15 +0300, Jani Nikula wrote:
>> Restrict hsync start, end, hdisplay and htotal to be according to hw
>> spec. Through drm_mode_set_crtcinfo(), these will also limit hblank start,
>> end.
>
> I'm pretty sure any physical hardware would balk at modes like this.
> Virtual framebuffers probably wouldn't care, I guess.  Still, seems
> wrong to have this in i915 when it should be common.
>
> Is this a problem we've seen in the wild, or is this just paranoia?

Looking at patch 2/2 I thought this would be a sensible thing to
do. That patch adds a check for a condition people might expect to work,
but doesn't, on Cantiga and later. It seemed a bit odd to merely add a
check for hsync_start == hdisplay while hsync_start < hdisplay (and the
other related conditions) would fail too.

BR,
Jani.