reproduce:
        git clone https://github.com/intel/lkp-tests.git ~/lkp-tests
        # apt-get install sparse
        # sparse version: v0.6.4-66-g0196afe1-dirty
        # https://git.kernel.org/pub/scm/linux/kernel/git/broonie/spi.git/commit/?id=9538edeb72c989a4b90964ae4bba107eaf21a791
        git remote add broonie-spi https://git.kernel.org/pub/scm/linux/kernel/git/broonie/spi.git
        git fetch --no-tags broonie-spi for-next
        git checkout 9538edeb72c989a4b90964ae4bba107eaf21a791
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        ~/lkp-tests/kbuild/make.cross C=1 CF='-fdiagnostic-prefix -D__CHECK_ENDIAN__ -fmax-errors=unlimited -fmax-warnings=unlimited' O=build_dir ARCH=mips olddefconfig
        ~/lkp-tests/kbuild/make.cross C=1 CF='-fdiagnostic-prefix -D__CHECK_ENDIAN__ -fmax-errors=unlimited -fmax-warnings=unlimited' O=build_dir ARCH=mips SHELL=/bin/bash drivers/spi/