reproduce:
        # apt-get install sparse
        # sparse version: v0.6.4-66-g0196afe1-dirty
        # https://git.kernel.org/pub/scm/linux/kernel/git/broonie/misc.git/commit/?id=3a0dac62f102669c43510607ddf5f630210bcc6a
        git remote add broonie-misc https://git.kernel.org/pub/scm/linux/kernel/git/broonie/misc.git
        git fetch --no-tags broonie-misc regmap-kunit-random-change
        git checkout 3a0dac62f102669c43510607ddf5f630210bcc6a
        # 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/base/regmap/