Hi Lyude, FYI, the error/warning still remains. tree: https://github.com/intel/linux-intel-lts.git 5.10/preempt-rt head: 92cafac7cc9c1af94b9b5b61e35fbbd39d4f5854 commit: ce5ae1651b65e1a62c2fd1c347a4a2473341bec7 [16339/17820] drm/nouveau/kms/nv50-: Add basic DPCD backlight support for nouveau config: powerpc-randconfig-c003-20211021 (attached as .config) compiler: clang version 14.0.0 (https://github.com/llvm/llvm-project 3cea2505fd8d99a9ba0cb625aecfe28a47c4e3f8) 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/intel/linux-intel-lts/commit/ce5ae1651b65e1a62c2fd1c34... git remote add intel-lts https://github.com/intel/linux-intel-lts.git git fetch --no-tags intel-lts 5.10/preempt-rt git checkout ce5ae1651b65e1a62c2fd1c347a4a2473341bec7 # save the attached .config to linux build tree mkdir build_dir COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 O=build_dir ARCH=powerpc SHELL=/bin/bash drivers/gpu/drm/ If you fix the issue, kindly add following tag as appropriate Reported-by: kernel test robot <lkp(a)intel.com&gt; All errors (new ones prefixed by >>): drivers/gpu/drm/nouveau/dispnv50/disp.c:1390:6: warning: variable 'ret' set but not used [-Wunused-but-set-variable] int ret; ^ drivers/gpu/drm/nouveau/dispnv50/disp.c:1414:6: warning: variable 'ret' set but not used [-Wunused-but-set-variable] int ret; ^ struct nouveau_backlight *backlight = nv_connector->backlight; ~~~~~~~~~~~~ ^ if (backlight && backlight->uses_dpcd) { ~~~~~~~~~^ drivers/gpu/drm/nouveau/dispnv50/disp.c:1665:9: note: forward declaration of 'struct nouveau_backlight' struct nouveau_backlight *backlight = nv_connector->backlight; ^ drivers/gpu/drm/nouveau/dispnv50/disp.c:1671:50: error: incomplete definition of type 'struct nouveau_backlight' ret = drm_edp_backlight_disable(aux, &backlight->edp_info); ~~~~~~~~~^ drivers/gpu/drm/nouveau/dispnv50/disp.c:1665:9: note: forward declaration of 'struct nouveau_backlight' struct nouveau_backlight *backlight = nv_connector->backlight; ^ drivers/gpu/drm/nouveau/dispnv50/disp.c:2661:1: warning: no previous prototype for function 'nv50_display_create' [-Wmissing-prototypes] nv50_display_create(struct drm_device *dev) ^ drivers/gpu/drm/nouveau/dispnv50/disp.c:2660:1: note: declare 'static' if the function is not intended to be used outside of this translation unit int ^ static 3 warnings and 3 errors generated. vim +1665 drivers/gpu/drm/nouveau/dispnv50/disp.c 1652 1653 /* TODO: Should we extend this to PWM-only backlights? 1654 * As well, should we add a DRM helper for waiting for the backlight to acknowledge 1655 * the panel backlight has been shut off? Intel doesn't seem to do this, and uses a 1656 * fixed time delay from the vbios… 1657 */ 1658 static void 1659 nv50_sor_atomic_disable(struct drm_encoder *encoder, struct drm_atomic_state *state) 1660 { 1661 struct nouveau_encoder *nv_encoder = nouveau_encoder(encoder); 1662 struct nouveau_drm *drm = nouveau_drm(nv_encoder->base.base.dev); 1663 struct nouveau_crtc *nv_crtc = nouveau_crtc(nv_encoder->crtc); 1664 struct nouveau_connector *nv_connector = nv50_outp_get_old_connector(state, nv_encoder); 1666 struct drm_dp_aux *aux = &nv_connector->aux; 1667 int ret; 1668 u8 pwr; 1669 1671 ret = drm_edp_backlight_disable(aux, &backlight->edp_info); 1672 if (ret < 0) 1673 NV_ERROR(drm, "Failed to disable backlight on [CONNECTOR:%d:%s]: %d\n", 1674 nv_connector->base.base.id, nv_connector->base.name, ret); 1675 } 1676 1677 if (nv_encoder->dcb->type == DCB_OUTPUT_DP) { 1678 int ret = drm_dp_dpcd_readb(aux, DP_SET_POWER, &pwr); 1679 1680 if (ret == 0) { 1681 pwr &= ~DP_SET_POWER_MASK; 1682 pwr |= DP_SET_POWER_D3; 1683 drm_dp_dpcd_writeb(aux, DP_SET_POWER, pwr); 1684 } 1685 } 1686 1687 nv_encoder->update(nv_encoder, nv_crtc->index, NULL, 0, 0); 1688 nv50_audio_disable(encoder, nv_crtc); 1689 nv50_hdmi_disable(&nv_encoder->base.base, nv_crtc); 1690 nv50_outp_release(nv_encoder); 1691 nv_encoder->crtc = NULL; 1692 } 1693 --- 0-DAY CI Kernel Test Service, Intel Corporation https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org