Hi Linus, FYI, the error/warning still remains. tree: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master head: daadb3bd0e8d3e317e36bc2c1542e86c528665e5 commit: d5d9f7ac58ea1041375a028f143ca5784693ea86 ARM/ixp4xx: Make NEED_MACH_IO_H optional date: 7 months ago config: arm-ixp4xx_defconfig (https://download.01.org/0day-ci/archive/20220113/202201130136.7675O5xx-lk...) compiler: clang version 14.0.0 (https://github.com/llvm/llvm-project 244dd2913a43a200f5a6544d424cdc37b771028b) 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 # install arm cross compiling tool for clang build # apt-get install binutils-arm-linux-gnueabi # 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 d5d9f7ac58ea1041375a028f143ca5784693ea86 # save the config file to linux build tree mkdir build_dir COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 O=build_dir ARCH=arm SHELL=/bin/bash 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 >>): arch/arm/mach-ixp4xx/common-pci.c:94:5: warning: no previous prototype for function 'ixp4xx_pci_read_errata' [-Wmissing-prototypes] int ixp4xx_pci_read_errata(u32 addr, u32 cmd, u32* data) ^ arch/arm/mach-ixp4xx/common-pci.c:94:1: note: declare 'static' if the function is not intended to be used outside of this translation unit int ixp4xx_pci_read_errata(u32 addr, u32 cmd, u32* data) ^ static arch/arm/mach-ixp4xx/common-pci.c:121:5: warning: no previous prototype for function 'ixp4xx_pci_read_no_errata' [-Wmissing-prototypes] int ixp4xx_pci_read_no_errata(u32 addr, u32 cmd, u32* data) ^ arch/arm/mach-ixp4xx/common-pci.c:121:1: note: declare 'static' if the function is not intended to be used outside of this translation unit int ixp4xx_pci_read_no_errata(u32 addr, u32 cmd, u32* data) ^ static int ixp4xx_pci_write(u32 addr, u32 cmd, u32 data) ^ arch/arm/mach-ixp4xx/common-pci.c:143:1: note: declare 'static' if the function is not intended to be used outside of this translation unit int ixp4xx_pci_write(u32 addr, u32 cmd, u32 data) ^ static 3 warnings generated. vim +/ixp4xx_pci_write +143 arch/arm/mach-ixp4xx/common-pci.c ^1da177e4c3f41 Linus Torvalds 2005-04-16 142 ^1da177e4c3f41 Linus Torvalds 2005-04-16 @143 int ixp4xx_pci_write(u32 addr, u32 cmd, u32 data) ^1da177e4c3f41 Linus Torvalds 2005-04-16 144 { ^1da177e4c3f41 Linus Torvalds 2005-04-16 145 unsigned long flags; ^1da177e4c3f41 Linus Torvalds 2005-04-16 146 int retval = 0; ^1da177e4c3f41 Linus Torvalds 2005-04-16 147 bd31b85960a7fc Thomas Gleixner 2009-07-03 148 raw_spin_lock_irqsave(&ixp4xx_pci_lock, flags); ^1da177e4c3f41 Linus Torvalds 2005-04-16 149 ^1da177e4c3f41 Linus Torvalds 2005-04-16 150 *PCI_NP_AD = addr; ^1da177e4c3f41 Linus Torvalds 2005-04-16 151 ^1da177e4c3f41 Linus Torvalds 2005-04-16 152 /* set up the write */ ^1da177e4c3f41 Linus Torvalds 2005-04-16 153 *PCI_NP_CBE = cmd; ^1da177e4c3f41 Linus Torvalds 2005-04-16 154 ^1da177e4c3f41 Linus Torvalds 2005-04-16 155 /* execute the write by writing to NP_WDATA */ ^1da177e4c3f41 Linus Torvalds 2005-04-16 156 *PCI_NP_WDATA = data; ^1da177e4c3f41 Linus Torvalds 2005-04-16 157 ^1da177e4c3f41 Linus Torvalds 2005-04-16 158 if(check_master_abort()) ^1da177e4c3f41 Linus Torvalds 2005-04-16 159 retval = 1; ^1da177e4c3f41 Linus Torvalds 2005-04-16 160 bd31b85960a7fc Thomas Gleixner 2009-07-03 161 raw_spin_unlock_irqrestore(&ixp4xx_pci_lock, flags); ^1da177e4c3f41 Linus Torvalds 2005-04-16 162 return retval; ^1da177e4c3f41 Linus Torvalds 2005-04-16 163 } ^1da177e4c3f41 Linus Torvalds 2005-04-16 164 :::::: The code at line 143 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