[jcmvbkbc-xtensa:xtensa-6.0-esp32 7/12] drivers/tty/serial/esp32_uart.c:33:6: warning: no previous prototype for function 'dbg_echo'

[jcmvbkbc-xtensa:xtensa-6.0-esp32 7/12] drivers/tty/serial/esp32_uart.c:33:6: warning: no previous prototype for function 'dbg_echo'

[kernel test robot]

tree:   https://github.com/jcmvbkbc/linux-xtensa xtensa-6.0-esp32
head:   513fb5af258c5311c5e0684c21db9aeb48e981e8
commit: a17e7b31fc865c922149feb5c560bc4c497b8c34 [7/12] WIP: drivers/tty/serial: add driver for ESP32 UART
config: riscv-randconfig-r032-20220921 (https://download.01.org/0day-ci/archive/20220921/202209212350.zedDtGpw-lkp@intel.com/config)
compiler: clang version 16.0.0 (https://github.com/llvm/llvm-project 791a7ae1ba3efd6bca96338e10ffde557ba83920)
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 riscv cross compiling tool for clang build
        # apt-get install binutils-riscv64-linux-gnu
        # https://github.com/jcmvbkbc/linux-xtensa/commit/a17e7b31fc865c922149feb5c560bc4c497b8c34
        git remote add jcmvbkbc-xtensa https://github.com/jcmvbkbc/linux-xtensa
        git fetch --no-tags jcmvbkbc-xtensa xtensa-6.0-esp32
        git checkout a17e7b31fc865c922149feb5c560bc4c497b8c34
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 O=build_dir ARCH=riscv SHELL=/bin/bash drivers/clk/ drivers/misc/ drivers/net/wireless/ralink/rt2x00/ drivers/pinctrl/ drivers/tty/serial/

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

All warnings (new ones prefixed by >>):

>> drivers/tty/serial/esp32_uart.c:33:6: warning: no previous prototype for function 'dbg_echo' [-Wmissing-prototypes]
   void dbg_echo(const char *s)
        ^
   drivers/tty/serial/esp32_uart.c:33:1: note: declare 'static' if the function is not intended to be used outside of this translation unit
   void dbg_echo(const char *s)
   ^
   static 
>> drivers/tty/serial/esp32_uart.c:48:6: warning: no previous prototype for function 'dbg_printf' [-Wmissing-prototypes]
   void dbg_printf(const char *fmt, ...)
        ^
   drivers/tty/serial/esp32_uart.c:48:1: note: declare 'static' if the function is not intended to be used outside of this translation unit
   void dbg_printf(const char *fmt, ...)
   ^
   static 
   2 warnings generated.


vim +/dbg_echo +33 drivers/tty/serial/esp32_uart.c

    32	
  > 33	void dbg_echo(const char *s)
    34	{
    35		volatile void __iomem *base = (volatile void __iomem *)0x3ff40000;
    36	
    37		while ((readl(base + UART_STATUS_REG) & UART_TXFIFO_CNT_MASK) != 0)
    38			;
    39	
    40		while (*s) {
    41			if (*s == '\n')
    42				writel('\r', base + UART_FIFO_REG);
    43			writel(*s, base + UART_FIFO_REG);
    44			++s;
    45		}
    46	}
    47	
  > 48	void dbg_printf(const char *fmt, ...)
    49	{
    50		va_list ap;
    51		char buf[256];
    52	
    53		va_start(ap, fmt);
    54		vsnprintf(buf, sizeof(buf), fmt, ap);
    55		va_end(ap);
    56		dbg_echo(buf);
    57	}
    58	

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