Hi Mauro, FYI, the error/warning still remains. tree: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master head: b2d229d4ddb17db541098b83524d901257e93845 commit: 238c84f71120f41c45301359902a912a19370f3d media: platform: rename exynos4-is/ to samsung/exynos4-is/ date: 5 weeks ago config: mips-randconfig-c004-20220418 (https://download.01.org/0day-ci/archive/20220419/202204192315.ZHbOex51-lkp@xxxxxxxxx/config) compiler: clang version 15.0.0 (https://github.com/llvm/llvm-project 429cbac0390654f90bba18a41799464adf31a5ec) reproduce (this is a W=1 build): wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross chmod +x ~/bin/make.cross # install mips cross compiling tool for clang build # apt-get install binutils-mips-linux-gnu # https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=238c84f71120f41c45301359902a912a19370f3d git remote add linus https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git git fetch --no-tags linus master git checkout 238c84f71120f41c45301359902a912a19370f3d # save the config file mkdir build_dir && cp config build_dir/.config COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 O=build_dir ARCH=mips SHELL=/bin/bash drivers/media/ If you fix the issue, kindly add following tag as appropriate Reported-by: kernel test robot <lkp@xxxxxxxxx> All warnings (new ones prefixed by >>): In file included from drivers/media/platform/samsung/exynos4-is/fimc-isp.c:25: >> drivers/media/platform/samsung/exynos4-is/fimc-isp-video.h:35:6: warning: no previous prototype for function 'fimc_isp_video_device_unregister' [-Wmissing-prototypes] void fimc_isp_video_device_unregister(struct fimc_isp *isp, ^ drivers/media/platform/samsung/exynos4-is/fimc-isp-video.h:35:1: note: declare 'static' if the function is not intended to be used outside of this translation unit void fimc_isp_video_device_unregister(struct fimc_isp *isp, ^ static 1 warning generated. vim +/fimc_isp_video_device_unregister +35 drivers/media/platform/samsung/exynos4-is/fimc-isp-video.h 34947b8aebe3f2 drivers/media/platform/exynos4-is/fimc-isp-video.h Sylwester Nawrocki 2013-12-20 34 34947b8aebe3f2 drivers/media/platform/exynos4-is/fimc-isp-video.h Sylwester Nawrocki 2013-12-20 @35 void fimc_isp_video_device_unregister(struct fimc_isp *isp, 34947b8aebe3f2 drivers/media/platform/exynos4-is/fimc-isp-video.h Sylwester Nawrocki 2013-12-20 36 enum v4l2_buf_type type) 34947b8aebe3f2 drivers/media/platform/exynos4-is/fimc-isp-video.h Sylwester Nawrocki 2013-12-20 37 { 34947b8aebe3f2 drivers/media/platform/exynos4-is/fimc-isp-video.h Sylwester Nawrocki 2013-12-20 38 } 34947b8aebe3f2 drivers/media/platform/exynos4-is/fimc-isp-video.h Sylwester Nawrocki 2013-12-20 39 #endif /* !CONFIG_VIDEO_EXYNOS4_ISP_DMA_CAPTURE */ 34947b8aebe3f2 drivers/media/platform/exynos4-is/fimc-isp-video.h Sylwester Nawrocki 2013-12-20 40 :::::: The code at line 35 was first introduced by commit :::::: 34947b8aebe3f2d4eceb65fceafa92bf8dc97d96 [media] exynos4-is: Add the FIMC-IS ISP capture DMA driver :::::: TO: Sylwester Nawrocki <s.nawrocki@xxxxxxxxxxx> :::::: CC: Mauro Carvalho Chehab <m.chehab@xxxxxxxxxxx> -- 0-DAY CI Kernel Test Service https://01.org/lkp