Making this IS_REACHABLE() was still wrong, as that just determines whether the lower-level backlight code would be reachable from the panel driver. However, with CONFIG_DRM=y and CONFIG_BACKLIGHT_CLASS_DEVICE=m, the drm_panel_of_backlight is left out of drm_panel.o but the condition tells the driver that it is there, leading to multiple link errors such as ERROR: "drm_panel_of_backlight" [drivers/gpu/drm/panel/panel-sitronix-st7701.ko] undefined! ERROR: "drm_panel_of_backlight" [drivers/gpu/drm/panel/panel-sharp-ls043t1le01.ko] undefined! ERROR: "drm_panel_of_backlight" [drivers/gpu/drm/panel/panel-seiko-43wvf1g.ko] undefined! ERROR: "drm_panel_of_backlight" [drivers/gpu/drm/panel/panel-ronbo-rb070d30.ko] undefined! ERROR: "drm_panel_of_backlight" [drivers/gpu/drm/panel/panel-rocktech-jh057n00900.ko] undefined! ERROR: "drm_panel_of_backlight" [drivers/gpu/drm/panel/panel-panasonic-vvx10f034n00.ko] undefined! ERROR: "drm_panel_of_backlight" [drivers/gpu/drm/panel/panel-osd-osd101t2587-53ts.ko] undefined! Change the condition to check for whether the function was actually part of the drm module. This version of the patch survived a few hundred randconfig builds, so I have a good feeling this might be the last one for the export. Fixes: 4a34a9dcec94 ("drm/drm_panel: Fix EXPORT of drm_panel_of_backlight() one more time") Fixes: 907aa265fde6 ("drm/drm_panel: fix EXPORT of drm_panel_of_backlight") Fixes: 152dbdeab1b2 ("drm/panel: add backlight support") Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx> --- include/drm/drm_panel.h | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/include/drm/drm_panel.h b/include/drm/drm_panel.h index 121f7aabccd1..6193cb555acc 100644 --- a/include/drm/drm_panel.h +++ b/include/drm/drm_panel.h @@ -198,7 +198,8 @@ static inline struct drm_panel *of_drm_find_panel(const struct device_node *np) } #endif -#if IS_REACHABLE(CONFIG_BACKLIGHT_CLASS_DEVICE) +#if IS_ENABLED(CONFIG_DRM_PANEL) && (IS_BUILTIN(CONFIG_BACKLIGHT_CLASS_DEVICE) || \ + (IS_MODULE(CONFIG_DRM) && IS_MODULE(CONFIG_BACKLIGHT_CLASS_DEVICE))) int drm_panel_of_backlight(struct drm_panel *panel); #else static inline int drm_panel_of_backlight(struct drm_panel *panel) -- 2.20.0 _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel