drm/kms: protect against fb helper not being created.

If drivers don't init the fb helper on the connector, the cmdline
code won't work, but it shouldn't crash either.

Signed-off-by: Dave Airlie <airlied@redhat.com>

1 files changed, 11 insertions, 2 deletions

diff --git a/drivers/gpu/drm/drm_crtc_helper.c b/drivers/gpu/drm/drm_crtc_helper.c
index 82fd6e82450f..1fe4e1d344fd 100644
--- a/drivers/gpu/drm/drm_crtc_helper.c
+++ b/drivers/gpu/drm/drm_crtc_helper.c
@@ -279,16 +279,25 @@ static struct drm_display_mode *drm_has_preferred_mode(struct drm_connector *con
 static bool drm_has_cmdline_mode(struct drm_connector *connector)
 {
         struct drm_fb_helper_connector *fb_help_conn = connector->fb_helper_private;
-        struct drm_fb_helper_cmdline_mode *cmdline_mode = &fb_help_conn->cmdline_mode;
+        struct drm_fb_helper_cmdline_mode *cmdline_mode;
+
+        if (!fb_help_conn)
+                return false;
+
+        cmdline_mode = &fb_help_conn->cmdline_mode;
         return cmdline_mode->specified;
 }
 
 static struct drm_display_mode *drm_pick_cmdline_mode(struct drm_connector *connector, int width, int height)
 {
         struct drm_fb_helper_connector *fb_help_conn = connector->fb_helper_private;
-        struct drm_fb_helper_cmdline_mode *cmdline_mode = &fb_help_conn->cmdline_mode;
+        struct drm_fb_helper_cmdline_mode *cmdline_mode;
         struct drm_display_mode *mode = NULL;
 
+        if (!fb_help_conn)
+                return mode;
+
+        cmdline_mode = &fb_help_conn->cmdline_mode;
         if (cmdline_mode->specified == false)
                 return mode;