Hi Chris, Thank you for the patch! Yet something to improve: [auto build test ERROR on jeyu/modules-next] [also build test ERROR on linux/master soc/for-next openrisc/for-next powerpc/next asm-generic/master linus/master v5.11-rc6 next-20210125] [cannot apply to tip/x86/core] [If your patch is applied to the wrong git tree, kindly drop us a note. And when submitting patch, we suggest to use '--base' as documented in https://git-scm.com/docs/git-format-patch] url: https://github.com/0day-ci/linux/commits/Chris-Down/printk-Userspace-format-enumeration-support/20210204-234240 base: https://git.kernel.org/pub/scm/linux/kernel/git/jeyu/linux.git modules-next config: um-x86_64_defconfig (attached as .config) compiler: gcc-9 (Debian 9.3.0-15) 9.3.0 reproduce (this is a W=1 build): # https://github.com/0day-ci/linux/commit/08a6039db35c32e39de288d58d0362013fdfb387 git remote add linux-review https://github.com/0day-ci/linux git fetch --no-tags linux-review Chris-Down/printk-Userspace-format-enumeration-support/20210204-234240 git checkout 08a6039db35c32e39de288d58d0362013fdfb387 # save the attached .config to linux build tree make W=1 ARCH=um SUBARCH=x86_64 If you fix the issue, kindly add following tag as appropriate Reported-by: kernel test robot All errors (new ones prefixed by >>): /usr/bin/ld: arch/um/drivers/xterm.o: in function `xterm_open': >> xterm.c:(.text+0x16b): undefined reference to `printk' >> /usr/bin/ld: xterm.c:(.text+0x1a8): undefined reference to `printk' /usr/bin/ld: xterm.c:(.text+0x1f4): undefined reference to `printk' /usr/bin/ld: xterm.c:(.text+0x25e): undefined reference to `printk' /usr/bin/ld: xterm.c:(.text+0x2b5): undefined reference to `printk' /usr/bin/ld: arch/um/drivers/xterm.o:xterm.c:(.text+0x31c): more undefined references to `printk' follow collect2: error: ld returned 1 exit status --- 0-DAY CI Kernel Test Service, Intel Corporation https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org