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

[kernel test robot]

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/?id=5ba3747dbc9ade2d22a8f5bff3c928cb41d35030
        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@xxxxxxxxx>

All warnings (new ones prefixed by >>):

>> arch/mips/boot/compressed/uart-prom.c:4:6: warning: no previous prototype for 'putc' [-Wmissing-prototypes]
       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@xxxxxxx>
:::::: CC: Ralf Baechle <ralf@xxxxxxxxxxxxxx>

---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all@xxxxxxxxxxxx

Attachment: .config.gz
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