reproduce:
        # apt-get install sparse
        # sparse version: v0.6.4-66-g0196afe1
        # https://github.com/jpirko/linux_mlxsw/commit/bfaae3e80b53d50093ec86eab85e522fb658e162
        git remote add jpirko-mlxsw https://github.com/jpirko/linux_mlxsw
        git fetch --no-tags jpirko-mlxsw combined_queue
        git checkout bfaae3e80b53d50093ec86eab85e522fb658e162
        # 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 net/ipv6/