In kernel 6.1 the backlight registration code was overhauled so that at most one backlight device got registered. As part of this change there was code added to cover the "nomodeset" case to still allow making an acpi_video0 device if the BIOS contained backlight control methods. This fallback logic however is failing on the BIOS from a number of motherboard manufacturers supporting Ryzen APUs. What happens is the amdgpu driver finishes registration and as expected doesn't create a backlight control device since no eDP panels are connected to a desktop. Then 8 seconds later the ACPI video detection code creates an acpi_video0 device that is non-operational. GNOME then creates a backlight slider. To avoid this situation from happening add support for video drivers to notify the ACPI video detection code that no panel was detected. To reduce the risk of regressions on multi-GPU systems: * only use this logic when the system is reported as a desktop enclosure. * in the amdgpu code only report into this for APUs. Mario Limonciello (2): ACPI: video: Allow GPU drivers to report no panels drm/amd/display: Report to ACPI video if no panels were found drivers/acpi/acpi_video.c | 12 ++++++++++++ drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 4 ++++ include/acpi/video.h | 1 + 3 files changed, 17 insertions(+) -- 2.34.1
