Hi Alistair, Thank you for the patch! Perhaps something to improve: [auto build test WARNING on robh/for-next] [also build test WARNING on linux/master linus/master v5.12-rc8 next-20210416] [If your patch is applied to the wrong git tree, kindly drop us a note. And when submitting patch, we suggest to use '--base' as documented in https://git-scm.com/docs/git-format-patch] url: https://github.com/0day-ci/linux/commits/Alistair-Francis/dt-bindings-Add... base: https://git.kernel.org/pub/scm/linux/kernel/git/robh/linux.git for-next config: powerpc-randconfig-r013-20210419 (attached as .config) compiler: clang version 13.0.0 (https://github.com/llvm/llvm-project 2b50f5a4343f8fb06acaa5c36355bcf58092c9cd) 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 powerpc cross compiling tool for clang build # apt-get install binutils-powerpc-linux-gnu # https://github.com/0day-ci/linux/commit/640f815589e788925b67d26bad5acec31... git remote add linux-review https://github.com/0day-ci/linux git fetch --no-tags linux-review Alistair-Francis/dt-bindings-Add-E-Ink-to-vendor-bindings/20210419-164835 git checkout 640f815589e788925b67d26bad5acec31594f456 # save the attached .config to linux build tree COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 ARCH=powerpc 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/powerpc/include/asm/io.h:537:62: note: expanded from macro '__do_outl' #define __do_outl(val, port) writel(val,(PCI_IO_ADDR)_IO_BASE+port); ~~~~~~~~~~~~~~~~~~~~~^ In file included from drivers/gpu/drm/panel/panel-simple.c:26: In file included from include/linux/iopoll.h:14: In file included from include/linux/io.h:13: In file included from arch/powerpc/include/asm/io.h:619: arch/powerpc/include/asm/io-defs.h:43:1: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic] DEF_PCI_AC_NORET(insb, (unsigned long p, void *b, unsigned long c), ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ arch/powerpc/include/asm/io.h:616:3: note: expanded from macro 'DEF_PCI_AC_NORET' __do_##name al; \ ^~~~~~~~~~~~~~ <scratch space>:187:1: note: expanded from here __do_insb ^ arch/powerpc/include/asm/io.h:556:56: note: expanded from macro '__do_insb' #define __do_insb(p, b, n) readsb((PCI_IO_ADDR)_IO_BASE+(p), (b), (n)) ~~~~~~~~~~~~~~~~~~~~~^ In file included from drivers/gpu/drm/panel/panel-simple.c:26: In file included from include/linux/iopoll.h:14: In file included from include/linux/io.h:13: In file included from arch/powerpc/include/asm/io.h:619: arch/powerpc/include/asm/io-defs.h:45:1: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic] DEF_PCI_AC_NORET(insw, (unsigned long p, void *b, unsigned long c), ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ arch/powerpc/include/asm/io.h:616:3: note: expanded from macro 'DEF_PCI_AC_NORET' __do_##name al; \ ^~~~~~~~~~~~~~ <scratch space>:189:1: note: expanded from here __do_insw ^ arch/powerpc/include/asm/io.h:557:56: note: expanded from macro '__do_insw' #define __do_insw(p, b, n) readsw((PCI_IO_ADDR)_IO_BASE+(p), (b), (n)) ~~~~~~~~~~~~~~~~~~~~~^ In file included from drivers/gpu/drm/panel/panel-simple.c:26: In file included from include/linux/iopoll.h:14: In file included from include/linux/io.h:13: In file included from arch/powerpc/include/asm/io.h:619: arch/powerpc/include/asm/io-defs.h:47:1: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic] DEF_PCI_AC_NORET(insl, (unsigned long p, void *b, unsigned long c), ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ arch/powerpc/include/asm/io.h:616:3: note: expanded from macro 'DEF_PCI_AC_NORET' __do_##name al; \ ^~~~~~~~~~~~~~ <scratch space>:191:1: note: expanded from here __do_insl ^ arch/powerpc/include/asm/io.h:558:56: note: expanded from macro '__do_insl' #define __do_insl(p, b, n) readsl((PCI_IO_ADDR)_IO_BASE+(p), (b), (n)) ~~~~~~~~~~~~~~~~~~~~~^ In file included from drivers/gpu/drm/panel/panel-simple.c:26: In file included from include/linux/iopoll.h:14: In file included from include/linux/io.h:13: In file included from arch/powerpc/include/asm/io.h:619: arch/powerpc/include/asm/io-defs.h:49:1: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic] DEF_PCI_AC_NORET(outsb, (unsigned long p, const void *b, unsigned long c), ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ arch/powerpc/include/asm/io.h:616:3: note: expanded from macro 'DEF_PCI_AC_NORET' __do_##name al; \ ^~~~~~~~~~~~~~ <scratch space>:193:1: note: expanded from here __do_outsb ^ arch/powerpc/include/asm/io.h:559:58: note: expanded from macro '__do_outsb' #define __do_outsb(p, b, n) writesb((PCI_IO_ADDR)_IO_BASE+(p),(b),(n)) ~~~~~~~~~~~~~~~~~~~~~^ In file included from drivers/gpu/drm/panel/panel-simple.c:26: In file included from include/linux/iopoll.h:14: In file included from include/linux/io.h:13: In file included from arch/powerpc/include/asm/io.h:619: arch/powerpc/include/asm/io-defs.h:51:1: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic] DEF_PCI_AC_NORET(outsw, (unsigned long p, const void *b, unsigned long c), ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ arch/powerpc/include/asm/io.h:616:3: note: expanded from macro 'DEF_PCI_AC_NORET' __do_##name al; \ ^~~~~~~~~~~~~~ <scratch space>:195:1: note: expanded from here __do_outsw ^ arch/powerpc/include/asm/io.h:560:58: note: expanded from macro '__do_outsw' #define __do_outsw(p, b, n) writesw((PCI_IO_ADDR)_IO_BASE+(p),(b),(n)) ~~~~~~~~~~~~~~~~~~~~~^ In file included from drivers/gpu/drm/panel/panel-simple.c:26: In file included from include/linux/iopoll.h:14: In file included from include/linux/io.h:13: In file included from arch/powerpc/include/asm/io.h:619: arch/powerpc/include/asm/io-defs.h:53:1: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic] DEF_PCI_AC_NORET(outsl, (unsigned long p, const void *b, unsigned long c), ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ arch/powerpc/include/asm/io.h:616:3: note: expanded from macro 'DEF_PCI_AC_NORET' __do_##name al; \ ^~~~~~~~~~~~~~ <scratch space>:197:1: note: expanded from here __do_outsl ^ arch/powerpc/include/asm/io.h:561:58: note: expanded from macro '__do_outsl' #define __do_outsl(p, b, n) writesl((PCI_IO_ADDR)_IO_BASE+(p),(b),(n)) ~~~~~~~~~~~~~~~~~~~~~^ static const struct display_timing eink_vb3300_kca_timing = { ^ 13 warnings generated. vim +/eink_vb3300_kca_timing +1967 drivers/gpu/drm/panel/panel-simple.c 1966 1968 .pixelclock = { 40000000, 40000000, 40000000 }, 1969 .hactive = { 334, 334, 334 }, 1970 .hfront_porch = { 1, 1, 1 }, 1971 .hback_porch = { 1, 1, 1 }, 1972 .hsync_len = { 1, 1, 1 }, 1973 .vactive = { 1405, 1405, 1405 }, 1974 .vfront_porch = { 1, 1, 1 }, 1975 .vback_porch = { 1, 1, 1 }, 1976 .vsync_len = { 1, 1, 1 }, 1977 .flags = DISPLAY_FLAGS_HSYNC_LOW | DISPLAY_FLAGS_VSYNC_LOW | 1978 DISPLAY_FLAGS_DE_HIGH | DISPLAY_FLAGS_PIXDATA_POSEDGE, 1979 }; 1980 --- 0-DAY CI Kernel Test Service, Intel Corporation https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org