Hi David, [FYI, it's a private test report for your RFC patch.] [auto build test WARNING on m68k/for-next] [also build test WARNING on sparc/master char-misc/char-misc-testing linus/master v5.12-rc3 next-20210319] [cannot apply to uclinux-h8/h8300-next hnaz-linux-mm/master] [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/David-Hildenbrand/drivers-char-r... base: https://git.kernel.org/pub/scm/linux/kernel/git/geert/linux-m68k.git for-next config: arm-randconfig-r014-20210318 (attached as .config) compiler: clang version 13.0.0 (https://github.com/llvm/llvm-project fcc1ce00931751ac02498986feb37744e9ace8de) 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 # install arm cross compiling tool for clang build # apt-get install binutils-arm-linux-gnueabi # https://github.com/0day-ci/linux/commit/7c68ea58a063d3f2d811e4b9cc0cee351... git remote add linux-review https://github.com/0day-ci/linux git fetch --no-tags linux-review David-Hildenbrand/drivers-char-remove-dev-kmem-for-good/20210319-223811 git checkout 7c68ea58a063d3f2d811e4b9cc0cee3514bed08f # save the attached .config to linux build tree COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross ARCH=arm 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 >>): long vwrite(char *buf, char *addr, unsigned long count) ^ mm/nommu.c:213:1: note: declare 'static' if the function is not intended to be used outside of this translation unit long vwrite(char *buf, char *addr, unsigned long count) ^ static mm/nommu.c:1658:15: warning: no previous prototype for function 'arch_get_unmapped_area' [-Wmissing-prototypes] unsigned long arch_get_unmapped_area(struct file *file, unsigned long addr, ^ mm/nommu.c:1658:1: note: declare 'static' if the function is not intended to be used outside of this translation unit unsigned long arch_get_unmapped_area(struct file *file, unsigned long addr, ^ static 2 warnings generated. vim +/vwrite +213 mm/nommu.c ^1da177e4c3f41 Linus Torvalds 2005-04-16 212 ^1da177e4c3f41 Linus Torvalds 2005-04-16 @213 long vwrite(char *buf, char *addr, unsigned long count) ^1da177e4c3f41 Linus Torvalds 2005-04-16 214 { ^1da177e4c3f41 Linus Torvalds 2005-04-16 215 /* Don't allow overflow */ ^1da177e4c3f41 Linus Torvalds 2005-04-16 216 if ((unsigned long) addr + count < count) ^1da177e4c3f41 Linus Torvalds 2005-04-16 217 count = -(unsigned long) addr; ^1da177e4c3f41 Linus Torvalds 2005-04-16 218 ^1da177e4c3f41 Linus Torvalds 2005-04-16 219 memcpy(addr, buf, count); ac7149045d9fcc Choi Gi-yong 2014-04-07 220 return count; ^1da177e4c3f41 Linus Torvalds 2005-04-16 221 } ^1da177e4c3f41 Linus Torvalds 2005-04-16 222 --- 0-DAY CI Kernel Test Service, Intel Corporation https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org