Subject: Re: [REGRESSION] next/master: (build) undefined reference to `devm_backlight_device_register' in vmlinux...

From: Randy Dunlap <[email-masked]>
Date: Wed, 15 Oct 2025 20:47:35 -0700

Guido,

Looks like this driver needs

+	depends on BACKLIGHT_CLASS_DEVICE

to fix the build.

@Gus- please read comments near bottom/end.

On 10/14/25 6:59 AM, KernelCI bot wrote:
> 
> 
> 
> 
> Hello,
> 
> New build issue found on next/master:
> 
> ---
>  undefined reference to `devm_backlight_device_register' in vmlinux.unstripped (drivers/gpu/drm/panel/panel-visionox-rm69299.c) [logspec:kbuild,kbuild.compiler.linker_error]
> ---
> 
> - dashboard: https://d.kernelci.org/i/maestro:c1e01dcc5d8b9be9ec47f44bbdb346c2464c0f02
> - giturl: https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git
> - commit HEAD:  13863a59e410cab46d26751941980dc8f088b9b3
> - tags: next-20251014
> 
> 
> Log excerpt:
> =====================================================
>   LD      .tmp_vmlinux1
> aarch64-linux-gnu-ld: Unexpected GOT/PLT entries detected!
> aarch64-linux-gnu-ld: Unexpected run-time procedure linkages detected!
> aarch64-linux-gnu-ld: drivers/gpu/drm/panel/panel-visionox-rm69299.o: in function `visionox_rm69299_create_backlight':
> /tmp/kci/linux/drivers/gpu/drm/panel/panel-visionox-rm69299.c:343: undefined reference to `devm_backlight_device_register'
> 
> =====================================================
> 
> 
> # Builds where the incident occurred:
> 
> ## defconfig+arm64-chromebook+CONFIG_ARM64_16K_PAGES=y on (arm64):
> - compiler: gcc-12
> - config: https://files.kernelci.org/kbuild-gcc-12-arm64-16k_pages-68ee4f14a6dc7c71db9fda21/.config
> - dashboard: https://d.kernelci.org/build/maestro:68ee4f14a6dc7c71db9fda21
> 
> ## defconfig+arm64-chromebook+CONFIG_ARM64_64K_PAGES=y on (arm64):
> - compiler: gcc-12
> - config: https://files.kernelci.org/kbuild-gcc-12-arm64-64k_pages-68ee4f17a6dc7c71db9fda24/.config
> - dashboard: https://d.kernelci.org/build/maestro:68ee4f17a6dc7c71db9fda24
> 
> ## defconfig+arm64-chromebook+CONFIG_CPU_BIG_ENDIAN=y+debug+kselftest+tinyconfig on (arm64):
> - compiler: gcc-12
> - config: https://files.kernelci.org/kbuild-gcc-12-arm64-mainline-big_endian-68ee4f32a6dc7c71db9fda39/.config
> - dashboard: https://d.kernelci.org/build/maestro:68ee4f32a6dc7c71db9fda39
> 
> ## defconfig+arm64-chromebook+CONFIG_RANDOMIZE_BASE=y on (arm64):
> - compiler: gcc-12
> - config: https://files.kernelci.org/kbuild-gcc-12-arm64-randomize-68ee4f1fa6dc7c71db9fda2a/.config
> - dashboard: https://d.kernelci.org/build/maestro:68ee4f1fa6dc7c71db9fda2a
> 
> ## defconfig+arm64-chromebook+kcidebug+lab-setup on (arm64):
> - compiler: gcc-12
> - config: https://files.kernelci.org/kbuild-gcc-12-arm64-chromebook-kcidebug-68ee4f2ba6dc7c71db9fda33/.config
> - dashboard: https://d.kernelci.org/build/maestro:68ee4f2ba6dc7c71db9fda33
> 
> ## defconfig+arm64-chromebook+kselftest on (arm64):
> - compiler: gcc-12
> - config: https://files.kernelci.org/kbuild-gcc-12-arm64-kselftest-16k_pages-68ee4f23a6dc7c71db9fda2d/.config
> - dashboard: https://d.kernelci.org/build/maestro:68ee4f23a6dc7c71db9fda2d
> 
> ## defconfig+arm64-chromebook+preempt_rt on (arm64):
> - compiler: gcc-12
> - config: https://files.kernelci.org/kbuild-gcc-12-arm64-preempt_rt_chromebook-68ee4f3aa6dc7c71db9fda3f/.config
> - dashboard: https://d.kernelci.org/build/maestro:68ee4f3aa6dc7c71db9fda3f
> 
> 
> #kernelci issue maestro:c1e01dcc5d8b9be9ec47f44bbdb346c2464c0f02
> 
> Reported-by: kernelci.org bot <[email-masked]>
> 
> --
> This is an experimental report format. Please send feedback in!
> Talk to us at [email-masked]
> 
> Made with love by the KernelCI team - https://kernelci.org
> 

Gus, the CI reporter needs to learn how to do a few things because developers
(other than me ?) don't scrounge mailing lists to look for problems.

a. find the commit that caused the problem (or the email series)

b. send the report (Cc:) to whoever wrote the patch and to the
appropriate mailing list.

I expect that b. is easier than a., so do it first.

And I'm sure that I have missed a thing or two that could be
added as well.

Thanks.

-- 
~Randy