tree: https://github.com/intel/linux-intel-lts.git 5.4/preempt-rt head: 6fa41e866e0be2824b0f5efb593f8635ee2a3bde commit: d8837af93a48e1acd496dd1074b7a5cfb93c046c [444/879] misc: vpusmm: add alloc/import DMABuf for VPU config: x86_64-randconfig-r002-20200820 (attached as .config) compiler: clang version 12.0.0 (https://github.com/llvm/llvm-project 4deda57106f7c9b982a49cb907c33e3966c8de7f) 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 x86_64 cross compiling tool for clang build # apt-get install binutils-x86-64-linux-gnu git checkout d8837af93a48e1acd496dd1074b7a5cfb93c046c # save the attached .config to linux build tree COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross ARCH=x86_64 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 >>): void vpusmm_dmabuf_release(struct dma_buf *dmabuf) ^ drivers/misc/vpusmm/vpusmm_driver.c:406:1: note: declare 'static' if the function is not intended to be used outside of this translation unit void vpusmm_dmabuf_release(struct dma_buf *dmabuf) ^ static 1 warning generated. # https://github.com/intel/linux-intel-lts/commit/d8837af93a48e1acd496dd107... git remote add intel-linux-intel-lts https://github.com/intel/linux-intel-lts.git git fetch --no-tags intel-linux-intel-lts 5.4/preempt-rt git checkout d8837af93a48e1acd496dd1074b7a5cfb93c046c vim +/vpusmm_dmabuf_release +406 drivers/misc/vpusmm/vpusmm_driver.c 405 407 { 408 // this buffer is only referencec by dmabuf 409 struct vpusmm_buffer *buff = dmabuf->priv; 410 411 if (buff) { 412 if (buff->cookie) { 413 dma_free_attrs(buff->dev, buff->size, buff->cookie, buff->dma_addr, buff->dma_attrs); 414 buff->cookie = NULL; 415 } 416 kfree(buff); 417 } 418 } 419 --- 0-DAY CI Kernel Test Service, Intel Corporation https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org