[PATCH] drm/i915: Prevent kernel panic on reading out compliance debugfs files

[Maarten Lankhorst <maarten.lankhorst@xxxxxxxxxxxxxxx>]

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.

Signed-off-by: Maarten Lankhorst <maarten.lankhorst@xxxxxxxxxxxxxxx>
---
 drivers/gpu/drm/i915/i915_debugfs.c | 33 ++++++++++++++++++++++++---------
 1 file changed, 24 insertions(+), 9 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_debugfs.c b/drivers/gpu/drm/i915/i915_debugfs.c
index 1f1176b6400e..30e2e168fe92 100644
--- a/drivers/gpu/drm/i915/i915_debugfs.c
+++ b/drivers/gpu/drm/i915/i915_debugfs.c
@@ -3812,13 +3812,18 @@ static int i915_displayport_test_active_show(struct seq_file *m, void *data)
 
 	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
@@ -3858,13 +3863,18 @@ static int i915_displayport_test_data_show(struct seq_file *m, void *data)
 
 	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",
@@ -3911,13 +3921,18 @@ static int i915_displayport_test_type_show(struct seq_file *m, void *data)
 
 	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");
-- 
2.11.0

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