reproduce (this is a W=1 build):
        # https://git.kernel.org/pub/scm/linux/kernel/git/jarkko/linux-tpmdd.git/commit/?id=127fa2ae9e2b1f9b9d876dfaa39fe3640cec5764
        git remote add jarkko-tpmdd https://git.kernel.org/pub/scm/linux/kernel/git/jarkko/linux-tpmdd.git
        git fetch --no-tags jarkko-tpmdd keys-trusted-next
        git checkout 127fa2ae9e2b1f9b9d876dfaa39fe3640cec5764
        # apt-get install sparse
        # sparse version: v0.6.4-71-g610d841d

        # 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 drivers/char/tpm/