Hi Dan, I love your patch! Yet something to improve: [auto build test ERROR on pavel-linux-leds/for-next] [cannot apply to j.anaszewski-leds/for-next] [if your patch is applied to the wrong git tree, please drop us a note to help improve the system. BTW, we also suggest to use '--base' option to specify the base tree in git format-patch, please see https://stackoverflow.com/a/37406982] url: https://github.com/0day-ci/linux/commits/Dan-Murphy/Multicolor-Framework-... base: git://git.kernel.org/pub/scm/linux/kernel/git/pavel/linux-leds.git for-next config: ia64-randconfig-r015-20200617 (attached as .config) compiler: ia64-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 # save the attached .config to linux build tree COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-9.3.0 make.cross ARCH=ia64 If you fix the issue, kindly add following tag as appropriate Reported-by: kernel test robot <lkp(a)intel.com&gt; All errors (new ones prefixed by >>, old ones prefixed by <<): ia64-linux-ld: drivers/leds/leds-lp55xx-common.o: in function `lp55xx_set_mc_brightness': >> drivers/leds/leds-lp55xx-common.c:146: undefined reference to `led_mc_calc_color_components' ia64-linux-ld: drivers/leds/leds-lp55xx-common.o: in function `devm_led_classdev_multicolor_register': >> include/linux/led-class-multicolor.h:74: undefined reference to `devm_led_classdev_multicolor_register_ext' vim +146 drivers/leds/leds-lp55xx-common.c 138 139 static int lp55xx_set_mc_brightness(struct led_classdev *cdev, 140 enum led_brightness brightness) 141 { 142 struct led_classdev_mc *mc_dev = lcdev_to_mccdev(cdev); 143 struct lp55xx_led *led = mcled_cdev_to_led(mc_dev); 144 struct lp55xx_device_config *cfg = led->chip->cfg; 145 > 146 led_mc_calc_color_components(&led->mc_cdev, brightness); 147 return cfg->multicolor_brightness_fn(led); 148