arch/mips/boot/compressed/uart-16550.c:44:6: warning: no previous prototype for 'putc'

[kernel test robot]

Hi YunQiang,

FYI, the error/warning still remains.

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
head:   9f266ccaa2f5228bfe67ad58a94ca4e0109b954a
commit: 31b2f3dc851c65fee288612432c4fc956f1a264e MIPS: enable both vmlinux.gz.itb and vmlinuz for generic
date:   1 year, 1 month ago
config: mips-randconfig-r006-20230202 (https://download.01.org/0day-ci/archive/20230203/202302030435.X9R1x5Ei-lkp@xxxxxxxxx/config)
compiler: mipsel-linux-gcc (GCC) 12.1.0
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=31b2f3dc851c65fee288612432c4fc956f1a264e
        git remote add linus https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
        git fetch --no-tags linus master
        git checkout 31b2f3dc851c65fee288612432c4fc956f1a264e
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-12.1.0 make.cross W=1 O=build_dir ARCH=mips olddefconfig
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-12.1.0 make.cross W=1 O=build_dir ARCH=mips SHELL=/bin/bash

If you fix the issue, kindly add following tag where applicable
| Reported-by: kernel test robot <lkp@xxxxxxxxx>

Note: functions only called from assembly code should be annotated with the asmlinkage attribute
All warnings (new ones prefixed by >>):

>> arch/mips/boot/compressed/uart-16550.c:44:6: warning: no previous prototype for 'putc' [-Wmissing-prototypes]
      44 | void putc(char c)
         |      ^~~~


vim +/putc +44 arch/mips/boot/compressed/uart-16550.c

1b93b3c3e94be2 Wu Zhangjin 2009-10-14  43  
1b93b3c3e94be2 Wu Zhangjin 2009-10-14 @44  void putc(char c)

:::::: The code at line 44 was first introduced by commit
:::::: 1b93b3c3e94be2605759735a89fc935ba5f58dcf MIPS: Add support for GZIP / BZIP2 / LZMA compressed kernel images

:::::: TO: Wu Zhangjin <wuzhangjin@xxxxxxxxx>
:::::: CC: Ralf Baechle <ralf@xxxxxxxxxxxxxx>

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests