reproduce:
        # apt-get install sparse
        # sparse version: v0.6.4-66-g0196afe1
        # https://git.kernel.org/pub/scm/linux/kernel/git/geert/renesas-drivers.git/commit/?id=42b54d52ecb7a81998592c2b40f8a963e82ed02e
        git remote add geert-renesas-drivers https://git.kernel.org/pub/scm/linux/kernel/git/geert/renesas-drivers.git
        git fetch --no-tags geert-renesas-drivers renesas-clk-for-v6.12
        git checkout 42b54d52ecb7a81998592c2b40f8a963e82ed02e
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        make W=1 C=1 CF='-fdiagnostic-prefix -D__CHECK_ENDIAN__ -fmax-errors=unlimited -fmax-warnings=unlimited' O=build_dir ARCH=um olddefconfig
        make W=1 C=1 CF='-fdiagnostic-prefix -D__CHECK_ENDIAN__ -fmax-errors=unlimited -fmax-warnings=unlimited' O=build_dir ARCH=um SHELL=/bin/bash