reproduce (this is a W=1 build):
        # https://git.kernel.org/pub/scm/linux/kernel/git/pci/pci.git/commit/?id=5ea26ba40d978b9f34faec2ca92c60e6d9db11c5
        git remote add pci https://git.kernel.org/pub/scm/linux/kernel/git/pci/pci.git
        git fetch --no-tags pci wip/2508-david-aspm-api
        git checkout 5ea26ba40d978b9f34faec2ca92c60e6d9db11c5
        # 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/char/