From: Arnd Bergmann arnd@arndb.de

commit ec7cc3f74b4236860ce612656aa5be7936d1c594 upstream.

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 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") Acked-by: Rob Herring robh@kernel.org # for drivers/of/ Link: https://lore.kernel.org/all/20210721151839.2484245-1-arnd@kernel.org/ Signed-off-by: Arnd Bergmann arnd@arndb.de Cc: Thomas Zimmermann tzimmermann@suse.de Cc: Daniel Vetter daniel.vetter@ffwll.ch # fbdev support Cc: Maxime Ripard maxime@cerno.tech Cc: Liam Girdwood lgirdwood@gmail.com Cc: Mark Brown broonie@kernel.org Cc: Daniel Vetter daniel.vetter@ffwll.ch Cc: Borislav Petkov bp@suse.de Cc: Javier Martinez Canillas javierm@redhat.com Cc: Randy Dunlap rdunlap@infradead.org Cc: Geert Uytterhoeven geert+renesas@glider.be Cc: Peter Collingbourne pcc@google.com Cc: Andy Shevchenko andriy.shevchenko@linux.intel.com Cc: dri-devel@lists.freedesktop.org Cc: linux-kernel@vger.kernel.org Cc: stable@vger.kernel.org # v5.14+ Signed-off-by: Thomas Zimmermann tzimmermann@suse.de Link: https://patchwork.freedesktop.org/patch/msgid/20210928145243.1098064-1-arnd@... Signed-off-by: Maarten Lankhorst maarten.lankhorst@linux.intel.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/of/base.c | 1 + drivers/video/fbdev/Kconfig | 5 +++-- 2 files changed, 4 insertions(+), 2 deletions(-)

--- a/drivers/of/base.c +++ b/drivers/of/base.c @@ -36,6 +36,7 @@ LIST_HEAD(aliases_lookup); struct device_node *of_root; EXPORT_SYMBOL(of_root); struct device_node *of_chosen; +EXPORT_SYMBOL(of_chosen); struct device_node *of_aliases; struct device_node *of_stdout; static const char *of_stdout_options; --- a/drivers/video/fbdev/Kconfig +++ b/drivers/video/fbdev/Kconfig @@ -2191,8 +2191,9 @@ config FB_HYPERV This framebuffer driver supports Microsoft Hyper-V Synthetic Video.

config FB_SIMPLE - bool "Simple framebuffer support" - depends on (FB = y) && !DRM_SIMPLEDRM + tristate "Simple framebuffer support" + depends on FB + depends on !DRM_SIMPLEDRM select FB_CFB_FILLRECT select FB_CFB_COPYAREA select FB_CFB_IMAGEBLIT