reproduce (this is a W=1 build):
        git checkout linus/master
        b4 shazam https://lore.kernel.org/r/20251209100313.2867-7-david.laight.linux@gmail.com
        # apt-get install sparse
        # sparse version: v0.6.4-73-gfbdde312

        # 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/pci/controller/