reproduce:
        # apt-get install sparse
        # sparse version: v0.6.4-66-g0196afe1
        # https://git.kernel.org/pub/scm/linux/kernel/git/pdx86/platform-drivers-x86.git/commit/?id=2282159b33580076235384597df1d62a6a1037ee
        git remote add pdx86-platform-drivers-x86 https://git.kernel.org/pub/scm/linux/kernel/git/pdx86/platform-drivers-x86.git
        git fetch --no-tags pdx86-platform-drivers-x86 for-next
        git checkout 2282159b33580076235384597df1d62a6a1037ee
        # 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/platform/x86/hp/