reproduce:
        # https://git.kernel.org/pub/scm/linux/kernel/git/bcain/linux.git/commit/?id=dd12099bfe857f1c7f5cd0915e38f655e8da5449
        git remote add bcain https://git.kernel.org/pub/scm/linux/kernel/git/bcain/linux.git
        git fetch --no-tags bcain bcain/glink
        git checkout dd12099bfe857f1c7f5cd0915e38f655e8da5449
        make menuconfig
        # enable CONFIG_COMPILE_TEST, CONFIG_WARN_MISSING_DOCUMENTS, CONFIG_WARN_ABI_ERRORS
        # pip install -r Documentation/sphinx/requirements.txt
        make htmldocs