Enabling the CONFIG_DRM_FBDEV_EMULATION Kconfig symbol can lead to linker
errors, if CONFIG_DRM_KMS_HELPER is built-in but CONFIG_FB as a module.
Because in that case the drm_kms_helper.o object will have references to
symbols that are defined in the fb.ko module, i.e:
$ make bzImage modules
DESCEND objtool
CALL scripts/atomic/check-atomics.sh
CALL scripts/checksyscalls.sh
CHK include/generated/compile.h
GEN .version
CHK include/generated/compile.h
UPD include/generated/compile.h
CC init/version.o
AR init/built-in.a
LD vmlinux.o
MODPOST vmlinux.symvers
MODINFO modules.builtin.modinfo
GEN modules.builtin
LD .tmp_vmlinux.kallsyms1
ld: drivers/gpu/drm/drm_fb_helper.o: in function `drm_fb_helper_resume_worker':
drm_fb_helper.c:(.text+0x2a0): undefined reference to `fb_set_suspend'
...
To prevent this, make following changes to the config option dependencies:
* Depend on FB && !(DRM_KMS_HELPER=y && FB=m), to avoid invalid configs.
* Depend on DRM_KMS_HELPER instead selecting it, to avoid circular deps.
Reported-by: Justin M. Forbes <[email protected]>
Signed-off-by: Javier Martinez Canillas <[email protected]>
---
This fixes linker errors found when building the Fedora kernel package
for the s390x architecture:
https://kojipkgs.fedoraproject.org//work/tasks/9849/77859849/build.log
drivers/gpu/drm/Kconfig | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/drivers/gpu/drm/Kconfig b/drivers/gpu/drm/Kconfig
index cea777ae7fb9..9a21e57b4a0d 100644
--- a/drivers/gpu/drm/Kconfig
+++ b/drivers/gpu/drm/Kconfig
@@ -103,8 +103,8 @@ config DRM_DEBUG_DP_MST_TOPOLOGY_REFS
config DRM_FBDEV_EMULATION
bool "Enable legacy fbdev support for your modesetting driver"
depends on DRM
- depends on FB
- select DRM_KMS_HELPER
+ depends on FB && !(DRM_KMS_HELPER=y && FB=m)
+ depends on DRM_KMS_HELPER
select FB_CFB_FILLRECT
select FB_CFB_COPYAREA
select FB_CFB_IMAGEBLIT
--
2.31.1
On Wed, 27 Oct 2021, Javier Martinez Canillas <[email protected]> wrote:
> Enabling the CONFIG_DRM_FBDEV_EMULATION Kconfig symbol can lead to linker
> errors, if CONFIG_DRM_KMS_HELPER is built-in but CONFIG_FB as a module.
>
> Because in that case the drm_kms_helper.o object will have references to
> symbols that are defined in the fb.ko module, i.e:
>
> $ make bzImage modules
> DESCEND objtool
> CALL scripts/atomic/check-atomics.sh
> CALL scripts/checksyscalls.sh
> CHK include/generated/compile.h
> GEN .version
> CHK include/generated/compile.h
> UPD include/generated/compile.h
> CC init/version.o
> AR init/built-in.a
> LD vmlinux.o
> MODPOST vmlinux.symvers
> MODINFO modules.builtin.modinfo
> GEN modules.builtin
> LD .tmp_vmlinux.kallsyms1
> ld: drivers/gpu/drm/drm_fb_helper.o: in function `drm_fb_helper_resume_worker':
> drm_fb_helper.c:(.text+0x2a0): undefined reference to `fb_set_suspend'
> ...
>
> To prevent this, make following changes to the config option dependencies:
>
> * Depend on FB && !(DRM_KMS_HELPER=y && FB=m), to avoid invalid configs.
> * Depend on DRM_KMS_HELPER instead selecting it, to avoid circular deps.
>
> Reported-by: Justin M. Forbes <[email protected]>
> Signed-off-by: Javier Martinez Canillas <[email protected]>
Please see [1]. I think it's a big mess. I don't think this is the fix
either.
BR,
Jani.
[1] https://lore.kernel.org/r/[email protected]
> ---
>
> This fixes linker errors found when building the Fedora kernel package
> for the s390x architecture:
>
> https://kojipkgs.fedoraproject.org//work/tasks/9849/77859849/build.log
>
> drivers/gpu/drm/Kconfig | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/Kconfig b/drivers/gpu/drm/Kconfig
> index cea777ae7fb9..9a21e57b4a0d 100644
> --- a/drivers/gpu/drm/Kconfig
> +++ b/drivers/gpu/drm/Kconfig
> @@ -103,8 +103,8 @@ config DRM_DEBUG_DP_MST_TOPOLOGY_REFS
> config DRM_FBDEV_EMULATION
> bool "Enable legacy fbdev support for your modesetting driver"
> depends on DRM
> - depends on FB
> - select DRM_KMS_HELPER
> + depends on FB && !(DRM_KMS_HELPER=y && FB=m)
> + depends on DRM_KMS_HELPER
> select FB_CFB_FILLRECT
> select FB_CFB_COPYAREA
> select FB_CFB_IMAGEBLIT
--
Jani Nikula, Intel Open Source Graphics Center