reproduce (this is a W=1 build):
        git clone https://github.com/intel/lkp-tests.git ~/lkp-tests
        # install riscv cross compiling tool for clang build
        # apt-get install binutils-riscv64-linux-gnu
        git remote add lee-backlight https://git.kernel.org/pub/scm/linux/kernel/git/lee/backlight.git
        git fetch lee-backlight for-backlight-next
        git checkout lee-backlight/for-backlight-next
        b4 shazam https://lore.kernel.org/r/20250407095119.588920-4-mitltlatltl@gmail.com
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang-21 ~/lkp-tests/kbuild/make.cross W=1 O=build_dir ARCH=riscv olddefconfig
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang-21 ~/lkp-tests/kbuild/make.cross W=1 O=build_dir ARCH=riscv SHELL=/bin/bash drivers/video/backlight/