drm/sun4i: link in front-end code if needed

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: dd0421f475 ("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>
Signed-off-by: Maxime Ripard <maxime.ripard@bootlin.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180706142847.2032381-1-arnd@arndb.de
This commit is contained in:
Arnd Bergmann 2018-07-06 16:28:28 +02:00 committed by Maxime Ripard
parent 44f9a4b0dc
commit 3156b53c2e
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@ -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