tree: https://git.kernel.org/pub/scm/linux/kernel/git/cip/linux-cip.git linux-4.19.y-cip head: 72750517bc5f1718ce3cb3fa75d4cadc05d27eee commit: cf532369d40146ffdd35f9d9a4558237c8773846 [11/17] drm: of: Add drm_of_lvds_get_dual_link_pixel_order config: parisc-randconfig-r001-20200809 (attached as .config) compiler: hppa-linux-gcc (GCC) 9.3.0 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 git checkout cf532369d40146ffdd35f9d9a4558237c8773846 # save the attached .config to linux build tree COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-9.3.0 make.cross ARCH=parisc 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 >>): In file included from drivers/gpu/drm/i2c/tda998x_drv.c:31: 95 | int drm_of_lvds_get_dual_link_pixel_order(const struct device_node *port1, | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ drivers/gpu/drm/i2c/tda998x_drv.c:1050:5: warning: no previous prototype for 'tda998x_audio_digital_mute' [-Wmissing-prototypes] 1050 | int tda998x_audio_digital_mute(struct device *dev, void *data, bool enable) | ^~~~~~~~~~~~~~~~~~~~~~~~~~ vim +/drm_of_lvds_get_dual_link_pixel_order +95 include/drm/drm_of.h 94 96 const struct device_node *port2) 97 { 98 return -EINVAL; 99 } 100 #endif 101 --- 0-DAY CI Kernel Test Service, Intel Corporation https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org