Hi Lai, FYI, the error/warning still remains. tree: https://github.com/intel/linux-intel-lts.git 5.4/preempt-rt head: 646a89c49751509d6493602ca6df16e229574d24 commit: 5e9e6d86fe729cf81e8a0df5c53d326b9f2ec791 [10119/19036] xlink-usb: XLink USB Remote and Local Host driver config: i386-allyesconfig (attached as .config) compiler: gcc-9 (Debian 9.3.0-22) 9.3.0 reproduce (this is a W=1 build): # https://github.com/intel/linux-intel-lts/commit/5e9e6d86fe729cf81e8a0df5c... git remote add intel-lts https://github.com/intel/linux-intel-lts.git git fetch --no-tags intel-lts 5.4/preempt-rt git checkout 5e9e6d86fe729cf81e8a0df5c53d326b9f2ec791 # save the attached .config to linux build tree make W=1 ARCH=i386 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 >>): drivers/misc/xlink-usb/local_host/f_vpuusb.c:349:5: warning: no previous prototype for 'mxlk_trigger_reset' [-Wmissing-prototypes] 349 | int mxlk_trigger_reset(void *arg) | ^~~~~~~~~~~~~~~~~~ drivers/misc/xlink-usb/local_host/f_vpuusb.c:377:5: warning: no previous prototype for 'vpu_setup' [-Wmissing-prototypes] 377 | int vpu_setup(struct usb_function *f, const struct usb_ctrlrequest *ctrl) | ^~~~~~~~~ drivers/misc/xlink-usb/local_host/f_vpuusb.c:525:5: warning: no previous prototype for 'vpu_cdc_notify' [-Wmissing-prototypes] 525 | int vpu_cdc_notify(struct f_acm *acm, u8 type, u16 value, | ^~~~~~~~~~~~~~ drivers/misc/xlink-usb/local_host/f_vpuusb.c:562:5: warning: no previous prototype for 'vpu_notify_serial_state' [-Wmissing-prototypes] 562 | int vpu_notify_serial_state(struct f_acm *acm) | ^~~~~~~~~~~~~~~~~~~~~~~ drivers/misc/xlink-usb/local_host/f_vpuusb.c: In function 'keembay_usb_irq_handler': 358 | int *data = vpu_read_swid(data); | ^~~~~~~~~~~~~~~~~~~ vim +/data +358 drivers/misc/xlink-usb/local_host/f_vpuusb.c 354 355 int intr; 356 static irqreturn_t keembay_usb_irq_handler(int irq, void *arg) 357 { 359 360 if (data != 0) { 361 if (*(data) == 0) 362 mxlk_trigger_reset(arg); 363 else { 364 if (!intr) { 365 bus_num = *(data); 366 intr = 1; 367 } else { 368 dev_num = *(data); 369 intr = 0; 370 } 371 } 372 } 373 374 return IRQ_HANDLED; 375 } 376 --- 0-DAY CI Kernel Test Service, Intel Corporation https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org