reproduce:
        # apt-get install sparse
        # sparse version: v0.6.4-66-g0196afe1
        # https://git.kernel.org/pub/scm/linux/kernel/git/superm1/linux.git/commit/?id=eaf3d006b20716b8e56a8dfe764144ff624e428f
        git remote add superm1 https://git.kernel.org/pub/scm/linux/kernel/git/superm1/linux.git
        git fetch --no-tags superm1 superm1/dsm-screen-on-off
        git checkout eaf3d006b20716b8e56a8dfe764144ff624e428f
        # 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=i386 olddefconfig
        make W=1 C=1 CF='-fdiagnostic-prefix -D__CHECK_ENDIAN__ -fmax-errors=unlimited -fmax-warnings=unlimited' O=build_dir ARCH=i386 SHELL=/bin/bash drivers/acpi/x86/