[PATCH 11/22] drm/amd/display: add NULL pointer check

[Qingqing Zhuo]

From: Charlene Liu <charlene....@amd.com>

[Why]
In virtual link use case, link->ddc could be NULL.

[How]
Add null pointer check to avoid undefined behavior.

Reviewed-by: Martin Leung <martin.le...@amd.com>
Reviewed-by: Hansen Dsouza <hansen.dso...@amd.com>
Acked-by: Qingqing Zhuo <qingqing.z...@amd.com>
Signed-off-by: Charlene Liu <charlene....@amd.com>
---
 .../amd/display/dc/dcn10/dcn10_hw_sequencer.c    | 16 ++++++++++------
 1 file changed, 10 insertions(+), 6 deletions(-)

diff --git a/drivers/gpu/drm/amd/display/dc/dcn10/dcn10_hw_sequencer.c 
b/drivers/gpu/drm/amd/display/dc/dcn10/dcn10_hw_sequencer.c
index acc7e40e4383..a1a29c508394 100644
--- a/drivers/gpu/drm/amd/display/dc/dcn10/dcn10_hw_sequencer.c
+++ b/drivers/gpu/drm/amd/display/dc/dcn10/dcn10_hw_sequencer.c
@@ -3223,12 +3223,16 @@ static void dcn10_config_stereo_parameters(
                        timing_3d_format == TIMING_3D_FORMAT_INBAND_FA ||
                        timing_3d_format == TIMING_3D_FORMAT_DP_HDMI_INBAND_FA 
||
                        timing_3d_format == TIMING_3D_FORMAT_SIDEBAND_FA) {
-                       enum display_dongle_type dongle = \
-                                       stream->link->ddc->dongle_type;
-                       if (dongle == DISPLAY_DONGLE_DP_VGA_CONVERTER ||
-                               dongle == DISPLAY_DONGLE_DP_DVI_CONVERTER ||
-                               dongle == DISPLAY_DONGLE_DP_HDMI_CONVERTER)
-                               flags->DISABLE_STEREO_DP_SYNC = 1;
+
+                       if (stream->link && stream->link->ddc) {
+                               enum display_dongle_type dongle = \
+                                               stream->link->ddc->dongle_type;
+
+                               if (dongle == DISPLAY_DONGLE_DP_VGA_CONVERTER ||
+                                       dongle == 
DISPLAY_DONGLE_DP_DVI_CONVERTER ||
+                                       dongle == 
DISPLAY_DONGLE_DP_HDMI_CONVERTER)
+                                       flags->DISABLE_STEREO_DP_SYNC = 1;
+                       }
                }
                flags->RIGHT_EYE_POLARITY =\
                                stream->timing.flags.RIGHT_EYE_3D_POLARITY;
-- 
2.25.1