linux-kernel - Re: [RFC PATCH 3/5] drm/i915: register LVDS connector even if we can't get a panel mode

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Message-ID: <20120803162451.GF8165@thinkpad-t410>
Date:	Fri, 3 Aug 2012 11:24:51 -0500
From:	Seth Forshee <seth.forshee@...onical.com>
To:	Matthew Garrett <mjg59@...f.ucam.org>
Cc:	dri-devel@...ts.freedesktop.org,
	Daniel Vetter <daniel.vetter@...ll.ch>,
	David Airlie <airlied@...ux.ie>, linux-kernel@...r.kernel.org,
	Andreas Heider <andreas@...tr.de>
Subject: Re: [RFC PATCH 3/5] drm/i915: register LVDS connector even if we
 can't get a panel mode

On Fri, Aug 03, 2012 at 05:14:16PM +0100, Matthew Garrett wrote:
> On Fri, Aug 03, 2012 at 11:02:19AM -0500, Seth Forshee wrote:
> > Some Apple hybrid graphics machines do not have the LVDS panel connected
> > to the integrated GPU at boot and also do not supply a VBT. The LVDS
> > connector is not registered as a result, making it impossible to support
> > graphics switching.
> > 
> > This patch changes intel_lvds_init() to register the connector even if
> > we can't find any panel modes. This makes it necessary to always check
> > intel_lvds->fixed_mode before use, as it could now be NULL.
> 
> This one kind of sucks. I think adding a quirk for this situation would 
> be justifiable, rather than doing it for all devices.

This is one of the things I wasn't so sure about. There are various
checks in intel_lvds_init() that can cause it to bail out before we try
to get the EDID, and I don't fully understand all of them. If non-laptop
machines are expected to bail out before the EDID check then the
approach I've taken seems reasonable. Otherwise adding a quirk probably
is a good idea.

Seth

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