[kbuild-all] arch/mips/boot/compressed/uart-prom.c:4:6: warning: no previous prototype for 'putc'

Hi Randy, First bad commit (maybe != root cause): tree: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master head: 881007522c8fcc3785c75432dbb149ca1b78e106 commit: 5ba3747dbc9ade2d22a8f5bff3c928cb41d35030 regulator: bd71815: add select to fix build date: 6 months ago config: mips-randconfig-r031-20210928 (attached as .config) compiler: mips-linux-gcc (GCC) 11.2.0 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://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit... git remote add linus https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git git fetch --no-tags linus master git checkout 5ba3747dbc9ade2d22a8f5bff3c928cb41d35030 # save the attached .config to linux build tree COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-11.2.0 make.cross ARCH=mips 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 >>): 4 | void putc(char c) | ^~~~ vim +/putc +4 arch/mips/boot/compressed/uart-prom.c dbb983145312ef Alban Bedel 2015-12-10 3 dbb983145312ef Alban Bedel 2015-12-10 @4 void putc(char c) :::::: The code at line 4 was first introduced by commit :::::: dbb983145312efba5f7928af1b180a0d83423150 MIPS: zboot: Add support for serial debug using the PROM :::::: TO: Alban Bedel <albeu(a)free.fr&gt; :::::: CC: Ralf Baechle <ralf(a)linux-mips.org&gt; --- 0-DAY CI Kernel Test Service, Intel Corporation https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org