From a874b6a3fb22c8c30f36b1f6ba5430a4c2278a6a Mon Sep 17 00:00:00 2001
From: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Date: Mon, 26 Jun 2017 10:18:35 +0200
Subject: [PATCH] drm/i915: Prevent kernel panic when reading/writing compliance debugfs files, v2.
Git-commit: a874b6a3fb22c8c30f36b1f6ba5430a4c2278a6a
Patch-mainline: v4.14-rc1
References: FATE#322643 bsc#1055900

When reading all debugfs files on a system with DP-MST the kernel panics
on a null pointer dereference because intel_dp is null for a DP-MST
connector. Detect this case and skip those connectors.

Also fix the write for the DP compliance file in the same way.

Changes since v1:
- Fix i915_displayport_test_active_write too. (DK)

Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Dhinakaran Pandiyan <dhinakaran.pandiyan@intel.com>
Cc: Manasi Navare <manasi.d.navare@intel.com>
Reviewed-by: Dhinakaran Pandiyan <dhinakaran.pandiyan@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170626081835.24251-1-maarten.lankhorst@linux.intel.com
Acked-by: Takashi Iwai <tiwai@suse.de>

---
 drivers/gpu/drm/i915/i915_debugfs.c |   44 ++++++++++++++++++++++++++----------
 1 file changed, 32 insertions(+), 12 deletions(-)

--- a/drivers/gpu/drm/i915/i915_debugfs.c
+++ b/drivers/gpu/drm/i915/i915_debugfs.c
@@ -3778,13 +3778,18 @@ static ssize_t i915_displayport_test_act
 
 	drm_connector_list_iter_begin(dev, &conn_iter);
 	drm_for_each_connector_iter(connector, &conn_iter) {
+		struct intel_encoder *encoder;
+
 		if (connector->connector_type !=
 		    DRM_MODE_CONNECTOR_DisplayPort)
 			continue;
 
-		if (connector->status == connector_status_connected &&
-		    connector->encoder != NULL) {
-			intel_dp = enc_to_intel_dp(connector->encoder);
+		encoder = to_intel_encoder(connector->encoder);
+		if (encoder && encoder->type == INTEL_OUTPUT_DP_MST)
+			continue;
+
+		if (encoder && connector->status == connector_status_connected) {
+			intel_dp = enc_to_intel_dp(&encoder->base);
 			status = kstrtoint(input_buffer, 10, &val);
 			if (status < 0)
 				break;
@@ -3816,13 +3821,18 @@ static int i915_displayport_test_active_
 
 	drm_connector_list_iter_begin(dev, &conn_iter);
 	drm_for_each_connector_iter(connector, &conn_iter) {
+		struct intel_encoder *encoder;
+
 		if (connector->connector_type !=
 		    DRM_MODE_CONNECTOR_DisplayPort)
 			continue;
 
-		if (connector->status == connector_status_connected &&
-		    connector->encoder != NULL) {
-			intel_dp = enc_to_intel_dp(connector->encoder);
+		encoder = to_intel_encoder(connector->encoder);
+		if (encoder && encoder->type == INTEL_OUTPUT_DP_MST)
+			continue;
+
+		if (encoder && connector->status == connector_status_connected) {
+			intel_dp = enc_to_intel_dp(&encoder->base);
 			if (intel_dp->compliance.test_active)
 				seq_puts(m, "1");
 			else
@@ -3862,13 +3872,18 @@ static int i915_displayport_test_data_sh
 
 	drm_connector_list_iter_begin(dev, &conn_iter);
 	drm_for_each_connector_iter(connector, &conn_iter) {
+		struct intel_encoder *encoder;
+
 		if (connector->connector_type !=
 		    DRM_MODE_CONNECTOR_DisplayPort)
 			continue;
 
-		if (connector->status == connector_status_connected &&
-		    connector->encoder != NULL) {
-			intel_dp = enc_to_intel_dp(connector->encoder);
+		encoder = to_intel_encoder(connector->encoder);
+		if (encoder && encoder->type == INTEL_OUTPUT_DP_MST)
+			continue;
+
+		if (encoder && connector->status == connector_status_connected) {
+			intel_dp = enc_to_intel_dp(&encoder->base);
 			if (intel_dp->compliance.test_type ==
 			    DP_TEST_LINK_EDID_READ)
 				seq_printf(m, "%lx",
@@ -3915,13 +3930,18 @@ static int i915_displayport_test_type_sh
 
 	drm_connector_list_iter_begin(dev, &conn_iter);
 	drm_for_each_connector_iter(connector, &conn_iter) {
+		struct intel_encoder *encoder;
+
 		if (connector->connector_type !=
 		    DRM_MODE_CONNECTOR_DisplayPort)
 			continue;
 
-		if (connector->status == connector_status_connected &&
-		    connector->encoder != NULL) {
-			intel_dp = enc_to_intel_dp(connector->encoder);
+		encoder = to_intel_encoder(connector->encoder);
+		if (encoder && encoder->type == INTEL_OUTPUT_DP_MST)
+			continue;
+
+		if (encoder && connector->status == connector_status_connected) {
+			intel_dp = enc_to_intel_dp(&encoder->base);
 			seq_printf(m, "%02lx", intel_dp->compliance.test_type);
 		} else
 			seq_puts(m, "0");