On Wed, Mar 14, 2018 at 12:01 AM, Thierry Reding thierry.reding@gmail.com wrote:
On Tue, Mar 13, 2018 at 09:59:54PM +0100, Arnd Bergmann wrote:
Like many other panel drivers, this one fails to build when backlight support is disabled:
drivers/gpu/drm/panel/panel-raydium-rm68200.o: In function `rm68200_probe': panel-raydium-rm68200.c:(.text+0x14a): undefined reference to `devm_of_find_backlight'
This adds the appropriate dependency.
Fixes: 2b7ed18bed1a ("drm/panel: Add support for Raydium RM68200 panel driver") Signed-off-by: Arnd Bergmann arnd@arndb.de
drivers/gpu/drm/panel/Kconfig | 1 + 1 file changed, 1 insertion(+)
This shouldn't be necessary. include/linux/backlight.h defines a stub if the backlight class is not enabled.
What tree are you seeing this on?
This is on linux-next.
It must be with BACKLIGHT_CLASS_DEVICE=m and DRM_PANEL_RAYDIUM_RM68200=y, meaning that it should be sufficient to do
depends on BACKLIGHT_CLASS_DEVICE || BACKLIGHT_CLASS_DEVICE=n
to force DRM_PANEL_RAYDIUM_RM68200 to be a loadable module whenever BACKLIGHT_CLASS_DEVICE=m. For the patch, I looked at what the other drivers in the same directory do and followed their example.
I see three options here:
1. update my patch changelog with the explanation I wrote here but leave it untouched 2. use the more elaborate dependency (after testing) but not change the others 3. change all panel drivers with a backlight dependency the same way, possibly with a helper symbol like
config BACKLIGHT_CLASS_DEVICE_OPTIONAL tristate default m if BACKLIGHT_CLASS_DEVICE=m default y
Arnd