On Wed, Jul 21, 2021 at 9:18 AM Arnd Bergmann arnd@kernel.org wrote:
From: Arnd Bergmann arnd@arndb.de
Configurations with both CONFIG_FB_SIMPLE=y and CONFIG_DRM_SIMPLEDRM=m are allowed by Kconfig because the 'depends on !DRM_SIMPLEDRM' dependency does not disallow FB_SIMPLE as long as SIMPLEDRM is not built-in. This
Double negative. How about:
allows FB_SIMPLE as long as SIMPLEDRM is not built-in.
can however result in a build failure when cfb_fillrect() etc are then also in loadable modules:
x86_64-linux-ld: drivers/video/fbdev/simplefb.o:(.rodata+0x1f8): undefined reference to `cfb_fillrect' x86_64-linux-ld: drivers/video/fbdev/simplefb.o:(.rodata+0x200): undefined reference to `cfb_copyarea' x86_64-linux-ld: drivers/video/fbdev/simplefb.o:(.rodata+0x208): undefined reference to `cfb_imageblit'
To work around this, change FB_SIMPLE to be a 'tristate' symbol, which still allows both to be =m together, but not one of them to be =y if the other one is =m. If a distro kernel picks this configuration, it can be determined by local policy which of the two modules gets loaded. The 'of_chosen' export is needed as this is the first loadable module referencing it.
Alternatively, the Kconfig dependency could be changed to 'depends on DRM_SIMPLEDRM=n', which would forbid the configuration with both drivers.
Fixes: 11e8f5fd223b ("drm: Add simpledrm driver") Signed-off-by: Arnd Bergmann arnd@arndb.de
drivers/of/base.c | 1 + drivers/video/fbdev/Kconfig | 5 +++-- 2 files changed, 4 insertions(+), 2 deletions(-)
For the DT change:
Acked-by: Rob Herring robh@kernel.org