reproduce (this is a W=1 build):
        # https://git.kernel.org/pub/scm/linux/kernel/git/djiang/linux.git/commit/?id=6576e541fcc39fd4f68ddaf2e4851d7eb30c9791
        git remote add djiang https://git.kernel.org/pub/scm/linux/kernel/git/djiang/linux.git
        git fetch --no-tags djiang cxl/extended-linear
        git checkout 6576e541fcc39fd4f68ddaf2e4851d7eb30c9791
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        make W=1 O=build_dir ARCH=x86_64 olddefconfig
        make W=1 O=build_dir ARCH=x86_64 SHELL=/bin/bash drivers/media/pci/cx25821/