Hi "Marek, Thank you for the patch! Perhaps something to improve: [auto build test WARNING on net-next/master] url: https://github.com/0day-ci/linux/commits/Marek-Beh-n/net-dsa-mv88e6xxx-Ad... base: https://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next.git e3ec1e8ca02b7e6c935bba3f9b6da86c2e57d2eb config: x86_64-randconfig-a006-20200818 (attached as .config) compiler: clang version 12.0.0 (https://github.com/llvm/llvm-project b34b1e38381fa4d1b1d9751a6b5233b68e734cfe) 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 x86_64 cross compiling tool for clang build # apt-get install binutils-x86-64-linux-gnu # save the attached .config to linux build tree COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross ARCH=x86_64 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 >>): return *lane == -1 ? -ENODEV : 0; ~~~~~ ^ ~~ drivers/net/dsa/mv88e6xxx/serdes.c:451:15: warning: result of comparison of constant -1 with expression of type 'u8' (aka 'unsigned char') is always false [-Wtautological-constant-out-of-range-compare] return *lane == -1 ? -ENODEV : 0; ~~~~~ ^ ~~ drivers/net/dsa/mv88e6xxx/serdes.c:526:15: warning: result of comparison of constant -1 with expression of type 'u8' (aka 'unsigned char') is always false [-Wtautological-constant-out-of-range-compare] return *lane == -1 ? -ENODEV : 0; ~~~~~ ^ ~~ 3 warnings generated. # https://github.com/0day-ci/linux/commit/a63db5e9b7db608109e7a315dfde9e57d... git remote add linux-review https://github.com/0day-ci/linux git fetch --no-tags linux-review Marek-Beh-n/net-dsa-mv88e6xxx-Add-Amethyst-88E6393X/20200819-234008 git checkout a63db5e9b7db608109e7a315dfde9e57df682a20 vim +428 drivers/net/dsa/mv88e6xxx/serdes.c 413 414 int mv88e6341_serdes_get_lane(struct mv88e6xxx_chip *chip, int port, u8 *lane) 415 { 416 u8 cmode = chip->ports[port].cmode; 417 418 *lane = -1; 419 switch (port) { 420 case 5: 421 if (cmode == MV88E6XXX_PORT_STS_CMODE_1000BASEX || 422 cmode == MV88E6XXX_PORT_STS_CMODE_SGMII || 423 cmode == MV88E6XXX_PORT_STS_CMODE_2500BASEX) 424 *lane = MV88E6341_PORT5_LANE; 425 break; 426 } 427 429 } 430 --- 0-DAY CI Kernel Test Service, Intel Corporation https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org