Hi Raymond, FYI, the error/warning still remains. tree: https://github.com/intel/linux-intel-lts.git 5.4/yocto head: 36f93ff941f127f4137ab369aecbdd995fb58c66 commit: e3b73159b8cfd2c940dd6e55702754c16f1f3923 [13550/20394] mfd: intel-ehl-gpio: Introduce MFD framework to PSE GPIO/TGPIO config: i386-allyesconfig (https://download.01.org/0day-ci/archive/20220122/202201222346.ttrLsdym-lk...) 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/e3b73159b8cfd2c940dd6e557... git remote add intel-lts https://github.com/intel/linux-intel-lts.git git fetch --no-tags intel-lts 5.4/yocto git checkout e3b73159b8cfd2c940dd6e55702754c16f1f3923 # save the config file to linux build tree mkdir build_dir make W=1 O=build_dir ARCH=i386 SHELL=/bin/bash drivers/mfd/ drivers/ptp/ 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/mfd/intel-ehl-gpio.c: In function 'intel_ehl_pse_gpio_mfd_suspend': drivers/mfd/intel-ehl-gpio.c:135:6: warning: unused variable 'i' [-Wunused-variable] 135 | int i = 0; | ^ drivers/mfd/intel-ehl-gpio.c: In function 'intel_ehl_pse_gpio_mfd_runtime_suspend': drivers/mfd/intel-ehl-gpio.c:184:6: warning: unused variable 'i' [-Wunused-variable] 184 | int i = 0; | ^ In file included from include/uapi/linux/posix_types.h:5, from include/uapi/linux/types.h:14, from include/linux/types.h:6, from include/linux/limits.h:6, from include/linux/kernel.h:7, from drivers/mfd/intel-ehl-gpio.c:14: drivers/mfd/intel-ehl-gpio.c: At top level: 8 | #define NULL ((void *)0) | ^ drivers/mfd/intel-ehl-gpio.c:236:32: note: in expansion of macro 'NULL' 236 | { PCI_VDEVICE(INTEL, 0x4b88), NULL}, | ^~~~ include/linux/stddef.h:8:14: note: (near initialization for 'intel_ehl_pse_gpio_mfd_ids[0].driver_data') 8 | #define NULL ((void *)0) | ^ drivers/mfd/intel-ehl-gpio.c:236:32: note: in expansion of macro 'NULL' 236 | { PCI_VDEVICE(INTEL, 0x4b88), NULL}, | ^~~~ 8 | #define NULL ((void *)0) | ^ drivers/mfd/intel-ehl-gpio.c:237:32: note: in expansion of macro 'NULL' 237 | { PCI_VDEVICE(INTEL, 0x4b89), NULL}, | ^~~~ include/linux/stddef.h:8:14: note: (near initialization for 'intel_ehl_pse_gpio_mfd_ids[1].driver_data') 8 | #define NULL ((void *)0) | ^ drivers/mfd/intel-ehl-gpio.c:237:32: note: in expansion of macro 'NULL' 237 | { PCI_VDEVICE(INTEL, 0x4b89), NULL}, | ^~~~ vim +8 include/linux/stddef.h ^1da177e4c3f41 Linus Torvalds 2005-04-16 6 ^1da177e4c3f41 Linus Torvalds 2005-04-16 7 #undef NULL ^1da177e4c3f41 Linus Torvalds 2005-04-16 @8 #define NULL ((void *)0) 6e218287432472 Richard Knutsson 2006-09-30 9 :::::: The code at line 8 was first introduced by commit :::::: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 Linux-2.6.12-rc2 :::::: TO: Linus Torvalds <torvalds(a)ppc970.osdl.org&gt; :::::: CC: Linus Torvalds <torvalds(a)ppc970.osdl.org&gt; --- 0-DAY CI Kernel Test Service, Intel Corporation https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org