reproduce:
        git checkout 5de07b8a24cf44cdb78adeab790704bf577c2c1d
        b4 shazam https://lore.kernel.org/r/20241206-apds9160-driver-v2-2-be2cb72ef8f4@dimonoff.com
        make menuconfig
        # enable CONFIG_COMPILE_TEST, CONFIG_WARN_MISSING_DOCUMENTS, CONFIG_WARN_ABI_ERRORS
        # install Sphinx 2.4.4
        make htmldocs