tree: https://git.kernel.org/pub/scm/linux/kernel/git/jirislaby/linux.git devel head: 0ecc0cdeaabd6b08ef3ec6dfaf724139031c00b8 commit: 2258e16ea4fe67f9700294b439b7aa1669aef643 [10/31] serial: make uart_console_write->putchar's character a char config: sparc-allyesconfig (https://download.01.org/0day-ci/archive/20220119/202201190151.92tNhDTm-lk...) compiler: sparc64-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/jirislaby/linux.git/commi... git remote add jirislaby https://git.kernel.org/pub/scm/linux/kernel/git/jirislaby/linux.git git fetch --no-tags jirislaby devel git checkout 2258e16ea4fe67f9700294b439b7aa1669aef643 # save the config file to linux build tree mkdir build_dir COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-11.2.0 make.cross O=build_dir ARCH=sparc SHELL=/bin/bash drivers/tty/serial/ 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 >>): drivers/tty/serial/sunzilog.c:1128:28: error: conflicting types for 'sunzilog_putchar'; have 'void(struct uart_port *, char)' 1128 | static void __maybe_unused sunzilog_putchar(struct uart_port *port, char ch) | ^~~~~~~~~~~~~~~~ drivers/tty/serial/sunzilog.c:103:13: note: previous declaration of 'sunzilog_putchar' with type 'void(struct uart_port *, int)' 103 | static void sunzilog_putchar(struct uart_port *port, int ch); | ^~~~~~~~~~~~~~~~ vim +/sunzilog_putchar +103 drivers/tty/serial/sunzilog.c ^1da177e4c3f41 drivers/serial/sunzilog.c Linus Torvalds 2005-04-16 102 6d45a1aed34b0c drivers/serial/sunzilog.c Jason Wessel 2010-05-20 @103 static void sunzilog_putchar(struct uart_port *port, int ch); 6d45a1aed34b0c drivers/serial/sunzilog.c Jason Wessel 2010-05-20 104 :::::: The code at line 103 was first introduced by commit :::::: 6d45a1aed34b0cd7b298967eb9cb72b77afcb33b sparc,sunzilog: Add console polling support for sunzilog serial driver :::::: TO: Jason Wessel <jason.wessel(a)windriver.com&gt; :::::: CC: Jason Wessel <jason.wessel(a)windriver.com&gt; --- 0-DAY CI Kernel Test Service, Intel Corporation https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org