From 06bfe5b0d892f8120172380694eb66eeb23baf90 Mon Sep 17 00:00:00 2001
From: Rodrigo Vivi <rodrigo.vivi@intel.com>
Date: Thu, 10 Aug 2017 07:50:43 -0700
Subject: [PATCH] drm/i915: Avoid null dereference if mst_port is unset.
Git-commit: 06bfe5b0d892f8120172380694eb66eeb23baf90
Patch-mainline: v4.14-rc1
References: FATE#322643 bsc#1055900

I'm not sure if this is really the case and I don't believe
this is the real fix for the bug mentioned here, but since
I don't see a reliable path when mst_port is set and when
mode_valid is requested I believe it is worth to have this
protection here.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=102022
Cc: Elizabeth <elizabethx.de.la.torre.mena@intel.com>
Cc: Stefan Assmann <sassmann@redhat.com>
Cc: Dhinakaran Pandiyan <dhinakaran.pandiyan@intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20170810145043.24047-1-rodrigo.vivi@intel.com
Acked-by: Takashi Iwai <tiwai@suse.de>

---
 drivers/gpu/drm/i915/intel_dp_mst.c |    3 +++
 1 file changed, 3 insertions(+)

--- a/drivers/gpu/drm/i915/intel_dp_mst.c
+++ b/drivers/gpu/drm/i915/intel_dp_mst.c
@@ -370,6 +370,9 @@ intel_dp_mst_mode_valid(struct drm_conne
 	int bpp = 24; /* MST uses fixed bpp */
 	int max_rate, mode_rate, max_lanes, max_link_clock;
 
+	if (!intel_dp)
+		return MODE_ERROR;
+
 	max_link_clock = intel_dp_max_link_rate(intel_dp);
 	max_lanes = intel_dp_max_lane_count(intel_dp);