Ubuntu
lxqt-config package

brightness keys on laptop don't dim the backlight

Bug #1829641 reported by Andrew
22
This bug affects 4 people
Affects Status Importance Assigned to Milestone
LXQt
New
Unknown
lxqt-config (Ubuntu)
Confirmed
Undecided
Unassigned

Bug Description

Normally on Ubuntu (and other OS e.g. Windows, OSX) the brightness keys on the keyboard adjust the backlight of the display so that you can reduce battery usage.

On Lubuntu/LXQT 19.04 they appear to adjust the brightness or contrast of the image instead, and the backlight is not adjusted.

This can be verified by opening the Brightness control panel which shows that the backlight slider (top) is not adjusted, instead the brightness 'wheel' is adjusted.

Description: Ubuntu 19.04
Release: 19.04

lxqt:
  Installed: (none)
  Candidate: 29
  Version table:
     29 500
        500 http://archive.ubuntu.com/ubuntu disco/universe amd64 Packages

Tags: lubuntu lxqt
Revision history for this message
Andrew (ajm83) wrote :
Revision history for this message
Andrew (ajm83) wrote :

I got a little further with this. I found that lxqt-config-brightness is the prorgram that is called when you press brightness up or down.

RUnning this on the terminal reveals the following:

lxqt-config-brightness -r
 (0x7ffe7dcde2b0) Debug: No outputs have backlight property
 (0x7ffe7dcde2b0) Debug: Found output: "eDP"
 (0x7ffe7dcde2b0) Debug: Output: "eDP" added
 (0x7ffe7dcde2b0) Debug: Found output: "HDMI-A-0"
 (0x7ffe7dcde2b0) Debug: Output is not connected

Note the message about backlight. Yet in all other Ubuntu flavours, and indeed the Brightness control panel on LXQT itself, I can adjust the backlight!!

Revision history for this message
Alf Gaida (agaida) wrote :

Thanks for confirming that this feature indeed works as expected.

Revision history for this message
ԜаӀtеr Ⅼарсһуnѕkі (wxl) wrote :

What "feature" are you referring to?

Revision history for this message
Alf Gaida (agaida) wrote :

Walter - the UI is horrible (really), but there are two things to consider - if the backlight can be adjusted the slider is enabled. If not, there is only the brightness control available.

PS: Horrible is the nicest word i can find for the state of the lxqt-config-brightness UI. Filed a bug a year ago iirc, but nobody stepped up and finally fixed it.

Revision history for this message
ԜаӀtеr Ⅼарсһуnѕkі (wxl) wrote :

Your bug is now linked, Alf. What about the brightness keys themselves, though?

affects: lxqt-powermanagement (Ubuntu) → lxqt-config (Ubuntu)
Revision history for this message
ԜаӀtеr Ⅼарсһуnѕkі (wxl) wrote :

Andrew, it seems `lxqt-config-brightness -d` should decrease the brightness and `lxqt-config-brightness -i` should increase it. Media keys XF86MonBrightnessUp/Down and Shift+Control+F6/7 are set in `lxqt-globalkeysd` to call these commands. It seems there is no option through `lxqt-config-brightness` to adjust the backlight. There is `lxqt-backlight_backend --inc/dec`, but it requires elevated permissions:
https://askubuntu.com/questions/1093862/lubuntu-brightness-backlight-issue

Revision history for this message
Andrew (ajm83) wrote :

Alf, the backlight CAN be adjusted with the dialog box, but not using the keys (which call lxqt-config-brightness). I can verify this by adjusting it then catting /sys/class/backlight/amdgpu_bl0/brightness :

Max
cat /sys/class/backlight/amdgpu_bl0/brightness
255

Min
cat /sys/class/backlight/amdgpu_bl0/brightness
13

I did chmod a+w on /sys/class/backlight/amdgpu_bl0/brightness to make absolutely sure it is accessible in case that is the issue, but it made no difference. lxqt-config-brightness -d and lxqt-config-brightness -i still adjust the brightness/gamma rather than the backlight.

Walter, I tried lxqt-backlight_backend --inc as in your link, but it does not work (as above, even after having changed the permissions on the /sys/class/backlight/amdgpu_bl0/brightness file:

retro@howard:~$ cat /sys/class/backlight/amdgpu_bl0/brightness
13
retro@howard:~$ lxqt-backlight_backend --inc
retro@howard:~$ lxqt-backlight_backend --inc
retro@howard:~$ lxqt-backlight_backend --inc
retro@howard:~$ lxqt-backlight_backend --inc
retro@howard:~$ lxqt-backlight_backend --inc
retro@howard:~$ lxqt-backlight_backend --inc
retro@howard:~$ lxqt-backlight_backend --inc
retro@howard:~$ lxqt-backlight_backend --inc
retro@howard:~$ cat /sys/class/backlight/amdgpu_bl0/brightness
13

Also as per comment #2, lxqt-config-brightness -r still returns "Debug: No outputs have backlight property"

Revision history for this message
Andrew (ajm83) wrote :

Alf, the backlight CAN be adjusted with the dialog box, but not using the keys (which call lxqt-config-brightness). I can verify this by adjusting it then catting /sys/class/backlight/amdgpu_bl0/brightness :

Max
cat /sys/class/backlight/amdgpu_bl0/brightness
255

Min
cat /sys/class/backlight/amdgpu_bl0/brightness
13

Note: this works even if the brightness file is read only to my user:
echo 123 > /sys/class/backlight/amdgpu_bl0/brightness
bash: /sys/class/backlight/amdgpu_bl0/brightness: Permission denied

After that test, I did chmod a+w on /sys/class/backlight/amdgpu_bl0/brightness to make absolutely sure it is accessible in case that is the issue with the keys, but it made no difference. lxqt-config-brightness -d and lxqt-config-brightness -i still adjust the brightness/gamma rather than the backlight.

Walter, I tried lxqt-backlight_backend --inc as in your link, but it does not work (as above, even after having changed the permissions on the /sys/class/backlight/amdgpu_bl0/brightness file:

retro@howard:~$ cat /sys/class/backlight/amdgpu_bl0/brightness
13
retro@howard:~$ lxqt-backlight_backend --inc
retro@howard:~$ lxqt-backlight_backend --inc
retro@howard:~$ lxqt-backlight_backend --inc
retro@howard:~$ lxqt-backlight_backend --inc
retro@howard:~$ lxqt-backlight_backend --inc
retro@howard:~$ lxqt-backlight_backend --inc
retro@howard:~$ lxqt-backlight_backend --inc
retro@howard:~$ lxqt-backlight_backend --inc
retro@howard:~$ cat /sys/class/backlight/amdgpu_bl0/brightness
13

Also as per comment #2, lxqt-config-brightness -r still returns "Debug: No outputs have backlight property" when the file is accessible.

Revision history for this message
Andrew (ajm83) wrote :

Sorry disregard #8 and read #9 instead, I've posted #8 accidentally before I finished editing it.

Revision history for this message
ԜаӀtеr Ⅼарсһуnѕkі (wxl) wrote :

We need some more information on your system. In particular, it would be nice to know what hardware you're working with. Maybe provide the results of `lspci -nnk`?

Bug Watch Updater (bug-watch-updater)
Changed in lxqt:
status: Unknown → New
Revision history for this message
Andrew (ajm83) wrote :
Download full text (4.1 KiB)

It's an Acer Swift 3 with AMD Ryzen 5 chipset/gpu.

Output from lspci -nnk:

00:00.0 Host bridge [0600]: Advanced Micro Devices, Inc. [AMD] Device [1022:15d0]
        Subsystem: Acer Incorporated [ALI] Device [1025:1233]
00:00.2 IOMMU [0806]: Advanced Micro Devices, Inc. [AMD] Device [1022:15d1]
        Subsystem: Acer Incorporated [ALI] Device [1025:1233]
00:01.0 Host bridge [0600]: Advanced Micro Devices, Inc. [AMD] Family 17h (Models 00h-0fh) PCIe Dummy Host Bridge [1022:1452]
00:01.7 PCI bridge [0604]: Advanced Micro Devices, Inc. [AMD] Device [1022:15d3]
        Kernel driver in use: pcieport
00:08.0 Host bridge [0600]: Advanced Micro Devices, Inc. [AMD] Family 17h (Models 00h-0fh) PCIe Dummy Host Bridge [1022:1452]
00:08.1 PCI bridge [0604]: Advanced Micro Devices, Inc. [AMD] Device [1022:15db]
        Kernel driver in use: pcieport
00:08.2 PCI bridge [0604]: Advanced Micro Devices, Inc. [AMD] Device [1022:15dc]
        Kernel driver in use: pcieport
00:14.0 SMBus [0c05]: Advanced Micro Devices, Inc. [AMD] FCH SMBus Controller [1022:790b] (rev 61)
        Subsystem: Acer Incorporated [ALI] FCH SMBus Controller [1025:1233]
        Kernel driver in use: piix4_smbus
        Kernel modules: i2c_piix4, sp5100_tco
00:14.3 ISA bridge [0601]: Advanced Micro Devices, Inc. [AMD] FCH LPC Bridge [1022:790e] (rev 51)
        Subsystem: Acer Incorporated [ALI] FCH LPC Bridge [1025:1233]
00:18.0 Host bridge [0600]: Advanced Micro Devices, Inc. [AMD] Device [1022:15e8]
00:18.1 Host bridge [0600]: Advanced Micro Devices, Inc. [AMD] Device [1022:15e9]
00:18.2 Host bridge [0600]: Advanced Micro Devices, Inc. [AMD] Device [1022:15ea]
00:18.3 Host bridge [0600]: Advanced Micro Devices, Inc. [AMD] Device [1022:15eb]
        Kernel driver in use: k10temp
        Kernel modules: k10temp
00:18.4 Host bridge [0600]: Advanced Micro Devices, Inc. [AMD] Device [1022:15ec]
00:18.5 Host bridge [0600]: Advanced Micro Devices, Inc. [AMD] Device [1022:15ed]
00:18.6 Host bridge [0600]: Advanced Micro Devices, Inc. [AMD] Device [1022:15ee]
00:18.7 Host bridge [0600]: Advanced Micro Devices, Inc. [AMD] Device [1022:15ef]
01:00.0 Network controller [0280]: Qualcomm Atheros QCA6174 802.11ac Wireless Network Adapter [168c:003e] (rev 32)
        Subsystem: Lite-On Communications Inc QCA6174 802.11ac Wireless Network Adapter [11ad:0807]
        Kernel driver in use: ath10k_pci
        Kernel modules: ath10k_pci
02:00.0 VGA compatible controller [0300]: Advanced Micro Devices, Inc. [AMD/ATI] Raven Ridge [Radeon Vega Series / Radeon Vega Mobile Series] [1002:15dd] (rev c4)
        Subsystem: Acer Incorporated [ALI] Raven Ridge [Radeon Vega Series / Radeon Vega Mobile Series] [1025:1233]
        Kernel driver in use: amdgpu
        Kernel modules: amdgpu
02:00.1 Audio device [0403]: Advanced Micro Devices, Inc. [AMD/ATI] Device [1002:15de]
        Subsystem: Acer Incorporated [ALI] Device [1025:1233]
        Kernel driver in use: snd_hda_intel
        Kernel modules: snd_hda_intel
02:00.2 Encryption controller [1080]: Advanced Micro Devices, Inc. [AMD] Device [1022:15df]
        Subsystem: Acer Incorporated [ALI] Device [1025:1233]
02:00.3 USB controller [0c03]: Advanced Micro Dev...

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Revision history for this message
Launchpad Janitor (janitor) wrote :

Status changed to 'Confirmed' because the bug affects multiple users.

Changed in lxqt-config (Ubuntu):
status: New → Confirmed
Revision history for this message
Gabriel (gabrc52) wrote :

I have an AMD E-300 APU with Radeon(tm) HD Graphics, and I'm facing this same issue on the latest Lubuntu 20.04

I've noted that `xbacklight` displays `No outputs have backlight property`. It seems that `lxqt-config-brightness` works the same way as `xbacklight`, or uses it internally.

However, `lxqt-backlight_backend` does work as intended after running `sudo chmod 0646 /sys/class/backlight/radeon_bl0/brightness`

Revision history for this message
Stefano (s-scarpone) wrote :
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I have a Lenovo IdeaPad 5 with and AMD Ryzen 5 and I have the same issue:
stefano@stefano-IdeaPad-5-15ARE05:~$ lspci -nnk
00:00.0 Host bridge [0600]: Advanced Micro Devices, Inc. [AMD] Renoir Root Complex [1022:1630]
 Subsystem: Advanced Micro Devices, Inc. [AMD] Renoir Root Complex [1022:1630]
00:00.2 IOMMU [0806]: Advanced Micro Devices, Inc. [AMD] Renoir IOMMU [1022:1631]
 Subsystem: Advanced Micro Devices, Inc. [AMD] Renoir IOMMU [1022:1631]
00:01.0 Host bridge [0600]: Advanced Micro Devices, Inc. [AMD] Renoir PCIe Dummy Host Bridge [1022:1632]
00:02.0 Host bridge [0600]: Advanced Micro Devices, Inc. [AMD] Renoir PCIe Dummy Host Bridge [1022:1632]
00:02.2 PCI bridge [0604]: Advanced Micro Devices, Inc. [AMD] Renoir PCIe GPP Bridge [1022:1634]
 Kernel driver in use: pcieport
00:02.4 PCI bridge [0604]: Advanced Micro Devices, Inc. [AMD] Renoir PCIe GPP Bridge [1022:1634]
 Kernel driver in use: pcieport
00:08.0 Host bridge [0600]: Advanced Micro Devices, Inc. [AMD] Renoir PCIe Dummy Host Bridge [1022:1632]
00:08.1 PCI bridge [0604]: Advanced Micro Devices, Inc. [AMD] Renoir Internal PCIe GPP Bridge to Bus [1022:1635]
 Kernel driver in use: pcieport
00:08.2 PCI bridge [0604]: Advanced Micro Devices, Inc. [AMD] Renoir Internal PCIe GPP Bridge to Bus [1022:1635]
 Kernel driver in use: pcieport
00:14.0 SMBus [0c05]: Advanced Micro Devices, Inc. [AMD] FCH SMBus Controller [1022:790b] (rev 51)
 Subsystem: Lenovo FCH SMBus Controller [17aa:3829]
 Kernel driver in use: piix4_smbus
 Kernel modules: i2c_piix4, sp5100_tco
00:14.3 ISA bridge [0601]: Advanced Micro Devices, Inc. [AMD] FCH LPC Bridge [1022:790e] (rev 51)
 Subsystem: Lenovo FCH LPC Bridge [17aa:3828]
00:18.0 Host bridge [0600]: Advanced Micro Devices, Inc. [AMD] Renoir Device 24: Function 0 [1022:1448]
00:18.1 Host bridge [0600]: Advanced Micro Devices, Inc. [AMD] Renoir Device 24: Function 1 [1022:1449]
00:18.2 Host bridge [0600]: Advanced Micro Devices, Inc. [AMD] Renoir Device 24: Function 2 [1022:144a]
00:18.3 Host bridge [0600]: Advanced Micro Devices, Inc. [AMD] Renoir Device 24: Function 3 [1022:144b]
 Kernel driver in use: k10temp
 Kernel modules: k10temp
00:18.4 Host bridge [0600]: Advanced Micro Devices, Inc. [AMD] Renoir Device 24: Function 4 [1022:144c]
00:18.5 Host bridge [0600]: Advanced Micro Devices, Inc. [AMD] Renoir Device 24: Function 5 [1022:144d]
00:18.6 Host bridge [0600]: Advanced Micro Devices, Inc. [AMD] Renoir Device 24: Function 6 [1022:144e]
00:18.7 Host bridge [0600]: Advanced Micro Devices, Inc. [AMD] Renoir Device 24: Function 7 [1022:144f]
01:00.0 Network controller [0280]: Intel Corporation Wi-Fi 6 AX200 [8086:2723] (rev 1a)
 Subsystem: Intel Corporation Wi-Fi 6 AX200 [8086:0080]
 Kernel driver in use: iwlwifi
 Kernel modules: iwlwifi
02:00.0 Non-Volatile memory controller [0108]: SK hynix Device [1c5c:1339]
 Subsystem: SK hynix Device [1c5c:0000]
 Kernel driver in use: nvme
 Kernel modules: nvme
03:00.0 VGA compatible controller [0300]: Advanced Micro Devices, Inc. [AMD/ATI] Renoir [1002:1636] (rev ce)
 Subsystem: Lenovo Renoir [17aa:381b]
 Kernel driver in use: amdgpu
 Kernel modules: amdgpu
03:00.1 Audio device [0403]: Advanced Micro Devices, Inc. [AMD/A...

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Stefano (s-scarpone) wrote :
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This is the modinfo output of amdgpu.ko kernel module I am using right now

stefano@stefano-IdeaPad-5-15ARE05:~$ modinfo amdgpu
filename: /lib/modules/5.9.8/kernel/drivers/gpu/drm/amd/amdgpu/amdgpu.ko
license: GPL and additional rights
description: AMD GPU
author: AMD linux driver team
firmware: amdgpu/navi12_gpu_info.bin
firmware: amdgpu/navi14_gpu_info.bin
firmware: amdgpu/navi10_gpu_info.bin
firmware: amdgpu/renoir_gpu_info.bin
firmware: amdgpu/arcturus_gpu_info.bin
firmware: amdgpu/raven2_gpu_info.bin
firmware: amdgpu/picasso_gpu_info.bin
firmware: amdgpu/raven_gpu_info.bin
firmware: amdgpu/vega12_gpu_info.bin
firmware: amdgpu/vega10_gpu_info.bin
firmware: amdgpu/mullins_mec.bin
firmware: amdgpu/mullins_rlc.bin
firmware: amdgpu/mullins_ce.bin
firmware: amdgpu/mullins_me.bin
firmware: amdgpu/mullins_pfp.bin
firmware: amdgpu/kabini_mec.bin
firmware: amdgpu/kabini_rlc.bin
firmware: amdgpu/kabini_ce.bin
firmware: amdgpu/kabini_me.bin
firmware: amdgpu/kabini_pfp.bin
firmware: amdgpu/kaveri_mec2.bin
firmware: amdgpu/kaveri_mec.bin
firmware: amdgpu/kaveri_rlc.bin
firmware: amdgpu/kaveri_ce.bin
firmware: amdgpu/kaveri_me.bin
firmware: amdgpu/kaveri_pfp.bin
firmware: amdgpu/hawaii_mec.bin
firmware: amdgpu/hawaii_rlc.bin
firmware: amdgpu/hawaii_ce.bin
firmware: amdgpu/hawaii_me.bin
firmware: amdgpu/hawaii_pfp.bin
firmware: amdgpu/bonaire_mec.bin
firmware: amdgpu/bonaire_rlc.bin
firmware: amdgpu/bonaire_ce.bin
firmware: amdgpu/bonaire_me.bin
firmware: amdgpu/bonaire_pfp.bin
firmware: amdgpu/mullins_sdma1.bin
firmware: amdgpu/mullins_sdma.bin
firmware: amdgpu/kabini_sdma1.bin
firmware: amdgpu/kabini_sdma.bin
firmware: amdgpu/kaveri_sdma1.bin
firmware: amdgpu/kaveri_sdma.bin
firmware: amdgpu/hawaii_sdma1.bin
firmware: amdgpu/hawaii_sdma.bin
firmware: amdgpu/bonaire_sdma1.bin
firmware: amdgpu/bonaire_sdma.bin
firmware: amdgpu/si58_mc.bin
firmware: amdgpu/hainan_mc.bin
firmware: amdgpu/oland_mc.bin
firmware: amdgpu/verde_mc.bin
firmware: amdgpu/pitcairn_mc.bin
firmware: amdgpu/tahiti_mc.bin
firmware: amdgpu/hainan_rlc.bin
firmware: amdgpu/hainan_ce.bin
firmware: amdgpu/hainan_me.bin
firmware: amdgpu/hainan_pfp.bin
firmware: amdgpu/oland_rlc.bin
firmware: amdgpu/oland_ce.bin
firmware: amdgpu/oland_me.bin
firmware: amdgpu/oland_pfp.bin
firmware: amdgpu/verde_rlc.bin
firmware: amdgpu/verde_ce.bin
firmware: amdgpu/verde_me.bin
firmware: amdgpu/verde_pfp.bin
firmware: amdgpu/pitcairn_rlc.bin
firmware: amdgpu/pitcairn_ce.bin
firmware: amdgpu/pitcairn_me.bin
firmware: amdgpu/pitcairn_pfp.bin
firmware: amdgpu/tahiti_rlc.bin
firmware: amdgpu/tahiti_ce.bin
firmware: amdgpu/tahiti_me.bin
firmware: amdgpu/tahiti_pfp.bin
firmware: amdgpu/banks_k_2_smc.bin
firmware: amdgpu/hainan_k_smc.bin
firmware: am...

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