When the base sun4i DRM driver is built-in but the back-end is a loadable module, we run into a link error:
drivers/gpu/drm/sun4i/sun4i_drv.o: In function `sun4i_drv_probe': sun4i_drv.c:(.text+0x60c): undefined reference to `sun4i_frontend_of_table'
The dependency is a bit tricky, the best workaround I have come up with is to use a Makefile hack to to interpret both CONFIG_DRM_SUN4I_BACKEND=m and CONFIG_DRM_SUN4I_BACKEND=y as a directive to build the front-end the same way as the main module.
Fixes: dd0421f47505 ("drm/sun4i: Add a driver for the display frontend") Link: https://lore.kernel.org/lkml/20180301091908.zcptz3ezqr2c6ly5@flea/ Signed-off-by: Arnd Bergmann arnd@arndb.de --- I stumbled over this one again when I sent a related patch. --- drivers/gpu/drm/sun4i/Makefile | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/drivers/gpu/drm/sun4i/Makefile b/drivers/gpu/drm/sun4i/Makefile index 3daed14941ca..11de3cd52dae 100644 --- a/drivers/gpu/drm/sun4i/Makefile +++ b/drivers/gpu/drm/sun4i/Makefile @@ -32,7 +32,10 @@ obj-$(CONFIG_DRM_SUN4I) += sun4i-tcon.o obj-$(CONFIG_DRM_SUN4I) += sun4i_tv.o obj-$(CONFIG_DRM_SUN4I) += sun6i_drc.o
-obj-$(CONFIG_DRM_SUN4I_BACKEND) += sun4i-backend.o sun4i-frontend.o +obj-$(CONFIG_DRM_SUN4I_BACKEND) += sun4i-backend.o +ifdef CONFIG_DRM_SUN4I_BACKEND +obj-$(CONFIG_DRM_SUN4I) += sun4i-frontend.o +endif obj-$(CONFIG_DRM_SUN4I_HDMI) += sun4i-drm-hdmi.o obj-$(CONFIG_DRM_SUN6I_DSI) += sun6i-dsi.o obj-$(CONFIG_DRM_SUN8I_DW_HDMI) += sun8i-drm-hdmi.o