Hi
Am 27.04.22 um 23:55 schrieb Javier Martinez Canillas:
The DRM_DP_AUX_CHARDEV and DRM_DP_CEC Kconfig symbols enable code that use DP helper functions, that are only present if CONFIG_DRM_DISPLAY_DP_HELPER is also enabled.
But these don't select the DRM_DISPLAY_DP_HELPER symbol, meaning that it is possible to enable any of them without CONFIG_DRM_DISPLAY_DP_HELPER.
That will lead to the following linking errors with the mentioned config:
LD vmlinux.o MODPOST vmlinux.symvers MODINFO modules.builtin.modinfo GEN modules.builtin LD .tmp_vmlinux.kallsyms1 KSYMS .tmp_vmlinux.kallsyms1.S AS .tmp_vmlinux.kallsyms1.S LD .tmp_vmlinux.kallsyms2 KSYMS .tmp_vmlinux.kallsyms2.S AS .tmp_vmlinux.kallsyms2.S LD vmlinux SYSMAP System.map SORTTAB vmlinux OBJCOPY arch/arm64/boot/Image MODPOST modules-only.symvers ERROR: modpost: "drm_dp_dpcd_write" [drivers/gpu/drm/display/drm_display_helper.ko] undefined! ERROR: modpost: "drm_dp_read_desc" [drivers/gpu/drm/display/drm_display_helper.ko] undefined! ERROR: modpost: "drm_dp_dpcd_read" [drivers/gpu/drm/display/drm_display_helper.ko] undefined! make[1]: *** [scripts/Makefile.modpost:134: modules-only.symvers] Error 1 make[1]: *** Deleting file 'modules-only.symvers' make: *** [Makefile:1749: modules] Error 2
Note: It seems this has been an issue for a long time but was made easier to reproduce after the commit 1e0f66420b13 ("drm/display: Introduce a DRM display-helper module"). Adding a Fixes: tag just to make sure that this fix will be picked for stable once the mentioned change also lands there.
Fixes: 1e0f66420b13 ("drm/display: Introduce a DRM display-helper module") Signed-off-by: Javier Martinez Canillas javierm@redhat.com
Changes in v2:
Explain better the issue in the change description.
Only select DRM_DISPLAY_DP_HELPER and not DRM_DISPLAY_HELPER.
drivers/gpu/drm/display/Kconfig | 2 ++ 1 file changed, 2 insertions(+)
diff --git a/drivers/gpu/drm/display/Kconfig b/drivers/gpu/drm/display/Kconfig index f84f1b0cd23f..9fe80c4e555c 100644 --- a/drivers/gpu/drm/display/Kconfig +++ b/drivers/gpu/drm/display/Kconfig @@ -32,6 +32,7 @@ config DRM_DISPLAY_HDMI_HELPER config DRM_DP_AUX_CHARDEV bool "DRM DP AUX Interface" depends on DRM
- select DRM_DISPLAY_DP_HELPER
You cannot select DISPLAY_DP_HELPER without DISPLAY_HELPER.
Can't you simply make it depend on DISPLAY_DP_HELPER. The menu entry will show up as soon as there's a driver that selcets DISPLAY_DP_HELPER.
Best regards Thomas
help Choose this option to enable a /dev/drm_dp_auxN node that allows to read and write values to arbitrary DPCD registers on the DP aux @@ -40,6 +41,7 @@ config DRM_DP_AUX_CHARDEV config DRM_DP_CEC bool "Enable DisplayPort CEC-Tunneling-over-AUX HDMI support" depends on DRM
- select DRM_DISPLAY_DP_HELPER select CEC_CORE help Choose this option if you want to enable HDMI CEC support for