Hi Oliver, I love your patch! Perhaps something to improve: [auto build test WARNING on net-next/master] url: https://github.com/0day-ci/linux/commits/Oliver-Hartkopp/can-isotp-implem... base: https://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next.git df41c19abbeaae6e24c8e31cff5fdb48632be380 config: xtensa-allyesconfig (attached as .config) compiler: xtensa-linux-gcc (GCC) 9.3.0 reproduce (this is a W=1 build): wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross chmod +x ~/bin/make.cross # https://github.com/0day-ci/linux/commit/693c9b4e8c5710e7b536ec9d6a969a7d7... git remote add linux-review https://github.com/0day-ci/linux git fetch --no-tags linux-review Oliver-Hartkopp/can-isotp-implement-cleanups-improvements-from-review/20201012-000055 git checkout 693c9b4e8c5710e7b536ec9d6a969a7d7343a100 # save the attached .config to linux build tree COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-9.3.0 make.cross ARCH=xtensa If you fix the issue, kindly add following tag as appropriate Reported-by: kernel test robot <lkp(a)intel.com&gt; All warnings (new ones prefixed by >>): 82 | #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt | In file included from include/linux/kernel.h:15, from include/linux/list.h:9, from include/linux/module.h:12, from net/can/isotp.c:56: include/linux/printk.h:297: note: this is the location of the previous definition 297 | #define pr_fmt(fmt) fmt | vim +/pr_fmt +82 net/can/isotp.c 81 83 --- 0-DAY CI Kernel Test Service, Intel Corporation https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org