At Display Next Hackfest 2026 we reviewed progress moving brightness control into the DRM connector properties.
There is a range LUMINANCE property that will default to 0->0. Once a driver attaches a backlight it will be updated to 1->max. If the panel supports the minimum backlight turning off the display the range can later be updated to 0->max instead of 1->max. The legacy sysfs interface is synchronized with the DRM connector. When a compositor using this feature is loaded, sysfs writes are disabled to prevent legacy tools from going out of sync with the compositor. This has an implementation initially for amdgpu, i915, and Xe with eDP connectors. It can be extended to other connectors like DP for displays that can be controlled via DDC as well later. For ease of testing; this series is also available on this branch: https://git.kernel.org/pub/scm/linux/kernel/git/superm1/linux.git/log/?h=superm1/backlight-property-v5 This tree is: * 7.1-rc5 + * Various patches coming from drm-next for amdgpu vblank handling + * This series These patches are backported into that branch due to timing bugs being exposed with this series. If this series is applied to drm-next those patches are not needed. The following compositors have implemented matching support: * Kwin: https://invent.kde.org/plasma/kwin/-/merge_requests/9298 * Mutter: https://gitlab.gnome.org/swick/mutter/-/commits/wip/kms-luminance-prop * Wlroots: https://gitlab.freedesktop.org/wlroots/wlroots/-/merge_requests/5384 --- v4->v5: * Add i915/xe support (Tested by Simon) * Drop driver indicating support as drivers will just add property to connectors * Lots of internal cleanups (see patches for details) * Add testing tags * Changes for bugs found in amdgpu handling when testing with Kwin * Use 1->max for default range, reserving 0 specifically for displays that are confirmed to turn off at minimum luminance. * Drop worker thread to notify brightness changes (handle part of the commit) * Drop amdgpu brightness caching Mario Limonciello (AMD) (11): Revert "backlight: Remove notifier" backlight: add kernel-internal backlight API drm: link connectors to backlight devices DRM: Add support for client indicating support for luminance drm/amd/display: Pass up errors reading actual brightness drm/amd/display: Allow backlight registration to fail drm/amd/display: Move backlight tracing out of the dc lock drm/amd/display: use drm backlight drm/amd/display: Drop brightness caching in amdgpu_dm drm/bridge: auto-link panel backlight in bridge connector drm/i915/display: use drm backlight drivers/gpu/drm/Kconfig | 1 + drivers/gpu/drm/Makefile | 1 + .../gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 117 ++--- .../gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.h | 13 - drivers/gpu/drm/bridge/panel.c | 15 + .../gpu/drm/display/drm_bridge_connector.c | 15 +- drivers/gpu/drm/drm_atomic_helper.c | 7 + drivers/gpu/drm/drm_atomic_uapi.c | 59 ++- drivers/gpu/drm/drm_backlight.c | 441 ++++++++++++++++++ drivers/gpu/drm/drm_connector.c | 63 +++ drivers/gpu/drm/drm_drv.c | 8 + drivers/gpu/drm/drm_file.c | 5 + drivers/gpu/drm/drm_ioctl.c | 15 + drivers/gpu/drm/drm_mode_config.c | 7 + drivers/gpu/drm/drm_mode_object.c | 66 ++- drivers/gpu/drm/drm_property.c | 6 + drivers/gpu/drm/drm_sysfs.c | 28 +- .../gpu/drm/i915/display/intel_backlight.c | 4 + drivers/gpu/drm/i915/display/intel_dp.c | 8 + drivers/video/backlight/backlight.c | 97 ++++ include/drm/drm_backlight.h | 51 ++ include/drm/drm_bridge.h | 1 + include/drm/drm_connector.h | 8 + include/drm/drm_file.h | 8 + include/drm/drm_mode_config.h | 5 + include/linux/backlight.h | 56 +++ include/uapi/drm/drm.h | 22 + 27 files changed, 1038 insertions(+), 89 deletions(-) create mode 100644 drivers/gpu/drm/drm_backlight.c create mode 100644 include/drm/drm_backlight.h -- 2.54.0
