Hi Chunfeng, FYI, the error/warning still remains. tree: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master head: bdcf11de8f776152c82d2197b255c2d04603f976 commit: a66ada4f241c9a5a0bbabc5af511ea5dd4c2cbb8 usb: gadget: bcm63xx_udc: create debugfs directory under usb root date: 10 months ago config: mips-randconfig-p002-20200921 (attached as .config) compiler: mips-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 a66ada4f241c9a5a0bbabc5af511ea5dd4c2cbb8 # save the attached .config to linux build tree COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-9.3.0 make.cross ARCH=mips 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 >>): drivers/usb/gadget/udc/bcm63xx_udc.c: In function 'bcm63xx_udc_init_debugfs': 2251 | root = debugfs_create_dir(udc->gadget.name, usb_debug_root); | ^~~~~~~~~~~~~~ drivers/usb/gadget/udc/bcm63xx_udc.c:2251:46: note: each undeclared identifier is reported only once for each function it appears in # https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit... git remote add linus https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git git fetch --no-tags linus master git checkout a66ada4f241c9a5a0bbabc5af511ea5dd4c2cbb8 vim +/usb_debug_root +2251 drivers/usb/gadget/udc/bcm63xx_udc.c 2239 2240 /** 2241 * bcm63xx_udc_init_debugfs - Create debugfs entries. 2242 * @udc: Reference to the device controller. 2243 */ 2244 static void bcm63xx_udc_init_debugfs(struct bcm63xx_udc *udc) 2245 { 2246 struct dentry *root; 2247 2248 if (!IS_ENABLED(CONFIG_USB_GADGET_DEBUG_FS)) 2249 return; 2250 2252 udc->debugfs_root = root; 2253 2254 debugfs_create_file("usbd", 0400, root, udc, &bcm63xx_usbd_dbg_fops); 2255 debugfs_create_file("iudma", 0400, root, udc, &bcm63xx_iudma_dbg_fops); 2256 } 2257 --- 0-DAY CI Kernel Test Service, Intel Corporation https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org