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

On 10/16/25 2:59 AM, Gustavo Padovan wrote:
> Hi Randy,
> 
> 
> ---- On Thu, 16 Oct 2025 00:47:35 -0300 Randy Dunlap <[email protected]> wrote ---
> 
>  > 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 protected]> 
>  > > 
>  > > -- 
>  > > This is an experimental report format. Please send feedback in! 
>  > > Talk to us at [email protected] 
>  > > 
>  > > 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. 
> 
> Absolutely. Our goal is to automate as many steps as possible!
>  
>  > 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. 
> 
> b. is easier that a. yes, but I don't think we can do it first because we
> need to figure the patch first. Essentially, you are asking us for
> build bisections. Something that is already on our roadmap, but
> we didn't had the time to tackle yet, but should come to it in the
> coming months.

Sometimes a bisect could be required. For cases such as this report,
a simple git blame or git log will show the culprit. Although coding
that is not as simple as a human looking at the screen.

>  >  
>  > And I'm sure that I have missed a thing or two that could be 
>  > added as well. 
> 
> Please keep the feedback coming!

-- 
~Randy