reproduce (this is a W=1 build):
        # https://git.kernel.org/pub/scm/linux/kernel/git/daeinki/drm-exynos.git/commit/?id=0810d5ad88a18f1e6d549853a388ad0316f74e36
        git remote add drm-exynos https://git.kernel.org/pub/scm/linux/kernel/git/daeinki/drm-exynos.git
        git fetch --no-tags drm-exynos exynos-drm-misc-next
        git checkout 0810d5ad88a18f1e6d549853a388ad0316f74e36
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        make W=1 O=build_dir ARCH=um olddefconfig
        make W=1 O=build_dir ARCH=um SHELL=/bin/bash drivers/accel/rocket/