Can't adjust screen brightness (Lenovo Laptop, NVIDIA, XFCE)

I’m having issues getting my screen brightness to change and would really appreciate any help. The Fn Keys and the brightness slider in the power manager system tray both appear like they’re working, in that the XFCE brightness pop-up is displayed and adjusted as expected and the values in the brightness file of /sys/class/backlight change, but the actual screen brightness seems stuck at 100%. When I first installed Manjaro some months ago the brightness keys worked (in a janky way: the brightness up worked but brightness down set brightness to 0/turned off the display), but either a kernel update or switching to proprietary NVIDIA drivers seem to have cut off the connection between my actual screen brightness and the brightness values I can manipulate, so I have been primarily using my windows install at night but want to get back to pure Manjaro.

I have tried manipulating my grub command-line options as per another forum post (can’t link), but that didn’t seem to help:
With no CMDLINE option, I have an acpi_video0 symlink in /sys/class/backlight, and it behaves as I described above (brightness file responding to FN Keys and the sytem tray slider from 0-100, screen brightness stuck at 100).
With GRUB_CMDLINE_LINUX="acpi_backlight=" none or native I get nothing in /sys/class/backlight, unresponsive brightness Fn Keys, and no slider in the system tray, and with the vendor option I get an ideapad symlink in /sys/class/backlight with a brightness file responsively changing from 0 to 16 but no actual screen brightness adjustment as with no CMDLINE option and the acpi_video0 brightness device, so I just went back to no grub CMDLINE option.

I have also tried switching to kernels 57 (same problem), and 59 (no boot), so I’ve gone back to 58.

I just recently found a workaround to change brightness manually by disabling redshift, executing xrandr --output DP-4 --brightness $value and then re-enabling redshift (if I don’t disable redshift it seems to reset the brightness value after a slight delay), but this is a little cumbersome and I’m wondering if there’s a better way to get the gui and laptop key brightness adjustment methods working.

In case they help diagnose my problem, here are my inxi -Fxxz:

System:    Kernel: 5.8.6-1-MANJARO x86_64 bits: 64 compiler: N/A Desktop: Xfce 4.14.2 tk: Gtk 3.24.20 wm: xfwm4 dm: LightDM 
           Distro: Manjaro Linux 
Machine:   Type: Laptop System: LENOVO product: 81SY v: Legion Y540-15IRH-PG0 serial: <filter> Chassis: type: 10 
           v: Legion Y540-15IRH-PG0 serial: <filter> 
           Mobo: LENOVO model: LNVNB161216 v: SDK0R32862 WIN serial: <filter> UEFI: LENOVO v: BHCN35WW date: 11/23/2019 
Battery:   ID-1: BAT0 charge: 31.5 Wh condition: 53.4/52.5 Wh (102%) volts: 11.6/11.3 model: LGC L17L3PG1 serial: <filter> 
           status: Unknown 
CPU:       Topology: 6-Core model: Intel Core i7-9750H bits: 64 type: MT MCP arch: Kaby Lake rev: A L2 cache: 12.0 MiB 
           flags: avx avx2 lm nx pae sse sse2 sse3 sse4_1 sse4_2 ssse3 vmx bogomips: 62431 
           Speed: 800 MHz min/max: 800/4500 MHz Core speeds (MHz): 1: 800 2: 800 3: 800 4: 800 5: 800 6: 800 7: 800 8: 800 
           9: 800 10: 800 11: 800 12: 800 
Graphics:  Device-1: NVIDIA TU117M [GeForce GTX 1650 Mobile / Max-Q] vendor: Lenovo driver: nvidia v: 440.100 bus ID: 01:00.0 
           chip ID: 10de:1f91 
           Device-2: Lite-On Integrated Camera type: USB driver: uvcvideo bus ID: 1-6:3 chip ID: 04ca:7070 
           Display: x11 server: X.Org 1.20.8 driver: nvidia resolution: 1920x1080~60Hz s-dpi: 96 
           OpenGL: renderer: GeForce GTX 1650/PCIe/SSE2 v: 4.6.0 NVIDIA 440.100 direct render: Yes 
Audio:     Device-1: Intel Cannon Lake PCH cAVS vendor: Lenovo driver: snd_hda_intel v: kernel bus ID: 00:1f.3 
           chip ID: 8086:a348 
           Device-2: NVIDIA vendor: Lenovo driver: snd_hda_intel v: kernel bus ID: 01:00.1 chip ID: 10de:10fa 
           Sound Server: ALSA v: k5.8.6-1-MANJARO 
Network:   Device-1: Intel Wireless-AC 9560 [Jefferson Peak] driver: iwlwifi v: kernel bus ID: 00:14.3 chip ID: 8086:a370 
           IF: wlp0s20f3 state: up mac: <filter> 
           Device-2: Realtek RTL8111/8168/8411 PCI Express Gigabit Ethernet vendor: Lenovo driver: r8169 v: kernel port: 3000 
           bus ID: 07:00.0 chip ID: 10ec:8168 
           IF: enp7s0 state: down mac: <filter> 
Drives:    Local Storage: total: 1.38 TiB used: 27.79 GiB (2.0%) 
           ID-1: /dev/nvme0n1 vendor: Samsung model: MZVLB512HBJQ-000L2 size: 476.94 GiB speed: 31.6 Gb/s lanes: 4 
           serial: <filter> 
           ID-2: /dev/sda vendor: Seagate model: ST1000LM049-2GH172 size: 931.51 GiB speed: 6.0 Gb/s serial: <filter> 
Partition: ID-1: / size: 95.13 GiB used: 14.30 GiB (15.0%) fs: ext4 dev: /dev/nvme0n1p6 
           ID-2: /home size: 406.44 GiB used: 13.49 GiB (3.3%) fs: ext4 dev: /dev/sda4 
Swap:      ID-1: swap-1 type: partition size: 7.45 GiB used: 0 KiB (0.0%) priority: -2 dev: /dev/sda3 
Sensors:   System Temperatures: cpu: 55.0 C mobo: N/A gpu: nvidia temp: 48 C 
           Fan Speeds (RPM): N/A 
Info:      Processes: 305 Uptime: 47m Memory: 15.56 GiB used: 2.97 GiB (19.1%) Init: systemd v: 246 Compilers: gcc: 10.2.0 
           Packages: pacman: 1136 Shell: Bash v: 5.0.18 running in: xfce4-terminal inxi: 3.1.05 

the contents of /etc/X11/mhwd.d:

==> mhwd.d/nvidia.conf <==
# nvidia-xconfig: X configuration file generated by nvidia-xconfig
# nvidia-xconfig:  version 440.82

Section "ServerLayout"
    Identifier     "Layout0"
    Screen      0  "Screen0"
    InputDevice    "Keyboard0" "CoreKeyboard"
    InputDevice    "Mouse0" "CorePointer"
EndSection

Section "Files"
EndSection

Section "InputDevice"
    # generated from default
    Identifier     "Mouse0"
    Driver         "mouse"
    Option         "Protocol" "auto"
    Option         "Device" "/dev/psaux"
    Option         "Emulate3Buttons" "no"
    Option         "ZAxisMapping" "4 5"
EndSection

Section "InputDevice"
    # generated from default
    Identifier     "Keyboard0"
    Driver         "kbd"
EndSection

Section "Monitor"
    Identifier     "Monitor0"
    VendorName     "Unknown"
    ModelName      "Unknown"
    Option         "DPMS"
EndSection

Section "Device"
    Identifier     "Device0"
    Driver         "nvidia"
    VendorName     "NVIDIA Corporation"
	Option "NoLogo" "1"
EndSection

Section "Screen"
    Identifier     "Screen0"
    Device         "Device0"
    Monitor        "Monitor0"
    DefaultDepth    24
    SubSection     "Display"
        Depth       24
    EndSubSection
EndSection

Section "Extensions"
    Option         "COMPOSITE" "Enable"
EndSection

 
Section "InputClass"
    Identifier          "Keyboard Defaults"
    MatchIsKeyboard        "yes"
    Option              "XkbOptions" "terminate:ctrl_alt_bksp"
EndSection
 

==> mhwd.d/nvidia.conf.nvidia-xconfig-original <==

and finally /etc/X11/xorg.conf.d:

==> xorg.conf.d/00-keyboard.conf <==
# Read and parsed by systemd-localed. It's probably wise not to edit this file
# manually too freely.
Section "InputClass"
        Identifier "system-keyboard"
        MatchIsKeyboard "on"
        Option "XkbLayout" "us"
        Option "XkbModel" "pc105"
EndSection

==> xorg.conf.d/90-mhwd.conf <==
# nvidia-xconfig: X configuration file generated by nvidia-xconfig
# nvidia-xconfig:  version 440.82

Section "ServerLayout"
    Identifier     "Layout0"
    Screen      0  "Screen0"
    InputDevice    "Keyboard0" "CoreKeyboard"
    InputDevice    "Mouse0" "CorePointer"
EndSection

Section "Files"
EndSection

Section "InputDevice"
    # generated from default
    Identifier     "Mouse0"
    Driver         "mouse"
    Option         "Protocol" "auto"
    Option         "Device" "/dev/psaux"
    Option         "Emulate3Buttons" "no"
    Option         "ZAxisMapping" "4 5"
EndSection

Section "InputDevice"
    # generated from default
    Identifier     "Keyboard0"
    Driver         "kbd"
EndSection

Section "Monitor"
    Identifier     "Monitor0"
    VendorName     "Unknown"
    ModelName      "Unknown"
    Option         "DPMS"
EndSection

Section "Device"
    Identifier     "Device0"
    Driver         "nvidia"
    VendorName     "NVIDIA Corporation"
	Option "NoLogo" "1"
EndSection

Section "Screen"
    Identifier     "Screen0"
    Device         "Device0"
    Monitor        "Monitor0"
    DefaultDepth    24
    SubSection     "Display"
        Depth       24
    EndSubSection
EndSection

Section "Extensions"
    Option         "COMPOSITE" "Enable"
EndSection

 
Section "InputClass"
    Identifier          "Keyboard Defaults"
    MatchIsKeyboard        "yes"
    Option              "XkbOptions" "terminate:ctrl_alt_bksp"
EndSection
 

If anyone has any suggestions/ideas they would be much appreciated.

Do I see that correctly that your laptop does not have an integrated gpu? I find that nigh unbelievable. Could you please run sudo mhwd -li and lspci -v and post the output?

1 Like

You’re right, it does have an iGPU, but in my BIOS boot menu there is an option to select between discrete graphics and switchable graphics, and for now I just have discrete graphics selected.

for sudo mhwd -li:

> Installed PCI configs:
--------------------------------------------------------------------------------
                  NAME               VERSION          FREEDRIVER           TYPE
--------------------------------------------------------------------------------
    video-nvidia-440xx            2019.10.25               false            PCI


Warning: No installed USB configs!

I think the no USB config could be related to a Possibly missing firmware for module: xhci_pci warning I get when the kernel builds with mkinitcpio? Not sure if it’s related to this issue, however.

lspci -v:

00:00.0 Host bridge: Intel Corporation 8th Gen Core Processor Host Bridge/DRAM Registers (rev 07)
	Subsystem: Lenovo Device 3807
	Flags: bus master, fast devsel, latency 0
	Capabilities: [e0] Vendor Specific Information: Len=10 <?>
	Kernel driver in use: skl_uncore

00:01.0 PCI bridge: Intel Corporation Xeon E3-1200 v5/E3-1500 v5/6th Gen Core Processor PCIe Controller (x16) (rev 07) (prog-if 00 [Normal decode])
	Flags: bus master, fast devsel, latency 0, IRQ 121
	Bus: primary=00, secondary=01, subordinate=05, sec-latency=0
	I/O behind bridge: 00004000-00004fff [size=4K]
	Memory behind bridge: b2000000-b30fffff [size=17M]
	Prefetchable memory behind bridge: 00000000a0000000-00000000b1ffffff [size=288M]
	Capabilities: [88] Subsystem: Lenovo Device 3812
	Capabilities: [80] Power Management version 3
	Capabilities: [90] MSI: Enable+ Count=1/1 Maskable- 64bit-
	Capabilities: [a0] Express Root Port (Slot+), MSI 00
	Capabilities: [100] Virtual Channel
	Capabilities: [140] Root Complex Link
	Capabilities: [d94] Secondary PCI Express
	Kernel driver in use: pcieport

00:04.0 Signal processing controller: Intel Corporation Xeon E3-1200 v5/E3-1500 v5/6th Gen Core Processor Thermal Subsystem (rev 07)
	Subsystem: Lenovo Device 382f
	Flags: bus master, fast devsel, latency 0, IRQ 16
	Memory at b3410000 (64-bit, non-prefetchable) [size=32K]
	Capabilities: [90] MSI: Enable- Count=1/1 Maskable- 64bit-
	Capabilities: [d0] Power Management version 3
	Capabilities: [e0] Vendor Specific Information: Len=0c <?>
	Kernel driver in use: proc_thermal
	Kernel modules: processor_thermal_device

00:08.0 System peripheral: Intel Corporation Xeon E3-1200 v5/v6 / E3-1500 v5 / 6th/7th/8th Gen Core Processor Gaussian Mixture Model
	Subsystem: Lenovo Device 3864
	Flags: bus master, fast devsel, latency 0, IRQ 255
	Memory at b3424000 (64-bit, non-prefetchable) [size=4K]
	Capabilities: [90] MSI: Enable- Count=1/1 Maskable- 64bit-
	Capabilities: [dc] Power Management version 2
	Capabilities: [f0] PCI Advanced Features

00:12.0 Signal processing controller: Intel Corporation Cannon Lake PCH Thermal Controller (rev 10)
	Subsystem: Lenovo Device 3802
	Flags: bus master, fast devsel, latency 0, IRQ 16
	Memory at b3425000 (64-bit, non-prefetchable) [size=4K]
	Capabilities: [50] Power Management version 3
	Capabilities: [80] MSI: Enable- Count=1/1 Maskable- 64bit-
	Kernel driver in use: intel_pch_thermal
	Kernel modules: intel_pch_thermal

00:14.0 USB controller: Intel Corporation Cannon Lake PCH USB 3.1 xHCI Host Controller (rev 10) (prog-if 30 [XHCI])
	Subsystem: Lenovo Device 3806
	Flags: bus master, medium devsel, latency 0, IRQ 138
	Memory at b3400000 (64-bit, non-prefetchable) [size=64K]
	Capabilities: [70] Power Management version 2
	Capabilities: [80] MSI: Enable+ Count=1/8 Maskable- 64bit+
	Capabilities: [90] Vendor Specific Information: Len=14 <?>
	Kernel driver in use: xhci_hcd
	Kernel modules: xhci_pci

00:14.2 RAM memory: Intel Corporation Cannon Lake PCH Shared SRAM (rev 10)
	Subsystem: Lenovo Device 3824
	Flags: bus master, fast devsel, latency 0
	Memory at b3420000 (64-bit, non-prefetchable) [size=8K]
	Memory at b3426000 (64-bit, non-prefetchable) [size=4K]
	Capabilities: [80] Power Management version 3

00:14.3 Network controller: Intel Corporation Wireless-AC 9560 [Jefferson Peak] (rev 10)
	Subsystem: Intel Corporation Device 0034
	Flags: bus master, fast devsel, latency 0, IRQ 16
	Memory at b3418000 (64-bit, non-prefetchable) [size=16K]
	Capabilities: [c8] Power Management version 3
	Capabilities: [d0] MSI: Enable- Count=1/1 Maskable- 64bit+
	Capabilities: [40] Express Root Complex Integrated Endpoint, MSI 00
	Capabilities: [80] MSI-X: Enable+ Count=16 Masked-
	Capabilities: [100] Null
	Capabilities: [14c] Latency Tolerance Reporting
	Capabilities: [164] Vendor Specific Information: ID=0010 Rev=0 Len=014 <?>
	Kernel driver in use: iwlwifi
	Kernel modules: iwlwifi

00:15.0 Serial bus controller [0c80]: Intel Corporation Cannon Lake PCH Serial IO I2C Controller #0 (rev 10)
	Subsystem: Lenovo Device 3803
	Flags: bus master, fast devsel, latency 0, IRQ 16
	Memory at b3427000 (64-bit, non-prefetchable) [size=4K]
	Capabilities: [80] Power Management version 3
	Capabilities: [90] Vendor Specific Information: Len=14 <?>
	Kernel driver in use: intel-lpss
	Kernel modules: intel_lpss_pci

00:15.1 Serial bus controller [0c80]: Intel Corporation Cannon Lake PCH Serial IO I2C Controller #1 (rev 10)
	Subsystem: Lenovo Device 3804
	Flags: bus master, fast devsel, latency 0, IRQ 17
	Memory at b3428000 (64-bit, non-prefetchable) [size=4K]
	Capabilities: [80] Power Management version 3
	Capabilities: [90] Vendor Specific Information: Len=14 <?>
	Kernel driver in use: intel-lpss
	Kernel modules: intel_lpss_pci

00:16.0 Communication controller: Intel Corporation Cannon Lake PCH HECI Controller (rev 10)
	Subsystem: Lenovo Device 3810
	Flags: bus master, fast devsel, latency 0, IRQ 139
	Memory at b3429000 (64-bit, non-prefetchable) [size=4K]
	Capabilities: [50] Power Management version 3
	Capabilities: [8c] MSI: Enable+ Count=1/1 Maskable- 64bit+
	Capabilities: [a4] Vendor Specific Information: Len=14 <?>
	Kernel driver in use: mei_me
	Kernel modules: mei_me

00:17.0 SATA controller: Intel Corporation Cannon Lake Mobile PCH SATA AHCI Controller (rev 10) (prog-if 01 [AHCI 1.0])
	Subsystem: Lenovo Device 3808
	Flags: bus master, 66MHz, medium devsel, latency 0, IRQ 124
	Memory at b3422000 (32-bit, non-prefetchable) [size=8K]
	Memory at b342e000 (32-bit, non-prefetchable) [size=256]
	I/O ports at 5040 [size=8]
	I/O ports at 5048 [size=4]
	I/O ports at 5020 [size=32]
	Memory at b342d000 (32-bit, non-prefetchable) [size=2K]
	Capabilities: [80] MSI: Enable+ Count=1/1 Maskable- 64bit-
	Capabilities: [70] Power Management version 3
	Capabilities: [a8] SATA HBA v1.0
	Kernel driver in use: ahci

00:1d.0 PCI bridge: Intel Corporation Cannon Lake PCH PCI Express Root Port #9 (rev f0) (prog-if 00 [Normal decode])
	Flags: bus master, fast devsel, latency 0, IRQ 122
	Bus: primary=00, secondary=06, subordinate=06, sec-latency=0
	I/O behind bridge: [disabled]
	Memory behind bridge: b3300000-b33fffff [size=1M]
	Prefetchable memory behind bridge: [disabled]
	Capabilities: [40] Express Root Port (Slot+), MSI 00
	Capabilities: [80] MSI: Enable+ Count=1/1 Maskable- 64bit-
	Capabilities: [90] Subsystem: Lenovo Device 381e
	Capabilities: [a0] Power Management version 3
	Capabilities: [100] Advanced Error Reporting
	Capabilities: [140] Access Control Services
	Capabilities: [150] Precision Time Measurement
	Capabilities: [200] L1 PM Substates
	Capabilities: [220] Secondary PCI Express
	Capabilities: [250] Downstream Port Containment
	Kernel driver in use: pcieport

00:1d.5 PCI bridge: Intel Corporation Cannon Lake PCH PCI Express Root Port #14 (rev f0) (prog-if 00 [Normal decode])
	Flags: bus master, fast devsel, latency 0, IRQ 123
	Bus: primary=00, secondary=07, subordinate=07, sec-latency=0
	I/O behind bridge: 00003000-00003fff [size=4K]
	Memory behind bridge: b3200000-b32fffff [size=1M]
	Prefetchable memory behind bridge: [disabled]
	Capabilities: [40] Express Root Port (Slot+), MSI 00
	Capabilities: [80] MSI: Enable+ Count=1/1 Maskable- 64bit-
	Capabilities: [90] Subsystem: Lenovo Device 3823
	Capabilities: [a0] Power Management version 3
	Capabilities: [100] Advanced Error Reporting
	Capabilities: [140] Access Control Services
	Capabilities: [150] Precision Time Measurement
	Capabilities: [200] L1 PM Substates
	Capabilities: [220] Secondary PCI Express
	Capabilities: [250] Downstream Port Containment
	Kernel driver in use: pcieport

00:1e.0 Communication controller: Intel Corporation Cannon Lake PCH Serial IO UART Host Controller (rev 10)
	Subsystem: Lenovo Device 3813
	Flags: bus master, fast devsel, latency 0, IRQ 20
	Memory at b342a000 (64-bit, non-prefetchable) [size=4K]
	Capabilities: [80] Power Management version 3
	Capabilities: [90] Vendor Specific Information: Len=14 <?>
	Kernel driver in use: intel-lpss
	Kernel modules: intel_lpss_pci

00:1f.0 ISA bridge: Intel Corporation HM470 Chipset LPC/eSPI Controller (rev 10)
	Subsystem: Lenovo Device 380e
	Flags: bus master, medium devsel, latency 0

00:1f.3 Audio device: Intel Corporation Cannon Lake PCH cAVS (rev 10)
	Subsystem: Lenovo Device 380f
	Flags: bus master, fast devsel, latency 32, IRQ 155
	Memory at b341c000 (64-bit, non-prefetchable) [size=16K]
	Memory at b3100000 (64-bit, non-prefetchable) [size=1M]
	Capabilities: [50] Power Management version 3
	Capabilities: [80] Vendor Specific Information: Len=14 <?>
	Capabilities: [60] MSI: Enable+ Count=1/1 Maskable- 64bit+
	Kernel driver in use: snd_hda_intel
	Kernel modules: snd_hda_intel, snd_soc_skl, snd_sof_pci

00:1f.4 SMBus: Intel Corporation Cannon Lake PCH SMBus Controller (rev 10)
	Subsystem: Lenovo Device 3814
	Flags: medium devsel, IRQ 16
	Memory at b342b000 (64-bit, non-prefetchable) [size=256]
	I/O ports at 5000 [size=32]
	Kernel driver in use: i801_smbus
	Kernel modules: i2c_i801

00:1f.5 Serial bus controller [0c80]: Intel Corporation Cannon Lake PCH SPI Controller (rev 10)
	Subsystem: Lenovo Device 3827
	Flags: bus master, fast devsel, latency 0
	Memory at fe010000 (32-bit, non-prefetchable) [size=4K]
	Kernel driver in use: intel-spi
	Kernel modules: intel_spi_pci

01:00.0 VGA compatible controller: NVIDIA Corporation TU117M [GeForce GTX 1650 Mobile / Max-Q] (rev a1) (prog-if 00 [VGA controller])
	Subsystem: Lenovo Device 3ffb
	Flags: bus master, fast devsel, latency 0, IRQ 156
	Memory at b2000000 (32-bit, non-prefetchable) [size=16M]
	Memory at a0000000 (64-bit, prefetchable) [size=256M]
	Memory at b0000000 (64-bit, prefetchable) [size=32M]
	I/O ports at 4000 [size=128]
	Expansion ROM at b3080000 [virtual] [disabled] [size=512K]
	Capabilities: [60] Power Management version 3
	Capabilities: [68] MSI: Enable+ Count=1/1 Maskable- 64bit+
	Capabilities: [78] Express Legacy Endpoint, MSI 00
	Capabilities: [100] Virtual Channel
	Capabilities: [250] Latency Tolerance Reporting
	Capabilities: [258] L1 PM Substates
	Capabilities: [128] Power Budgeting <?>
	Capabilities: [420] Advanced Error Reporting
	Capabilities: [600] Vendor Specific Information: ID=0001 Rev=1 Len=024 <?>
	Capabilities: [900] Secondary PCI Express
	Capabilities: [bb0] Physical Resizable BAR
	Kernel driver in use: nvidia
	Kernel modules: nouveau, nvidia_drm, nvidia

01:00.1 Audio device: NVIDIA Corporation Device 10fa (rev a1)
	Subsystem: Lenovo Device 3ffb
	Flags: bus master, fast devsel, latency 0, IRQ 17
	Memory at b3000000 (32-bit, non-prefetchable) [size=16K]
	Capabilities: [60] Power Management version 3
	Capabilities: [68] MSI: Enable- Count=1/1 Maskable- 64bit+
	Capabilities: [78] Express Endpoint, MSI 00
	Capabilities: [100] Advanced Error Reporting
	Kernel driver in use: snd_hda_intel
	Kernel modules: snd_hda_intel

06:00.0 Non-Volatile memory controller: Samsung Electronics Co Ltd NVMe SSD Controller SM981/PM981/PM983 (prog-if 02 [NVM Express])
	Subsystem: Samsung Electronics Co Ltd Device a801
	Flags: bus master, fast devsel, latency 0, IRQ 16, NUMA node 0
	Memory at b3300000 (64-bit, non-prefetchable) [size=16K]
	Capabilities: [40] Power Management version 3
	Capabilities: [50] MSI: Enable- Count=1/32 Maskable- 64bit+
	Capabilities: [70] Express Endpoint, MSI 00
	Capabilities: [b0] MSI-X: Enable+ Count=33 Masked-
	Capabilities: [100] Advanced Error Reporting
	Capabilities: [148] Device Serial Number 00-00-00-00-00-00-00-00
	Capabilities: [158] Power Budgeting <?>
	Capabilities: [168] Secondary PCI Express
	Capabilities: [188] Latency Tolerance Reporting
	Capabilities: [190] L1 PM Substates
	Kernel driver in use: nvme

07:00.0 Ethernet controller: Realtek Semiconductor Co., Ltd. RTL8111/8168/8411 PCI Express Gigabit Ethernet Controller (rev 15)
	Subsystem: Lenovo Device 38cd
	Flags: bus master, fast devsel, latency 0, IRQ 17
	I/O ports at 3000 [size=256]
	Memory at b3204000 (64-bit, non-prefetchable) [size=4K]
	Memory at b3200000 (64-bit, non-prefetchable) [size=16K]
	Capabilities: [40] Power Management version 3
	Capabilities: [50] MSI: Enable- Count=1/1 Maskable- 64bit+
	Capabilities: [70] Express Endpoint, MSI 01
	Capabilities: [b0] MSI-X: Enable+ Count=4 Masked-
	Capabilities: [100] Advanced Error Reporting
	Capabilities: [140] Virtual Channel
	Capabilities: [160] Device Serial Number 01-00-00-00-68-4c-e0-00
	Capabilities: [170] Latency Tolerance Reporting
	Capabilities: [178] L1 PM Substates
	Kernel driver in use: r8169
	Kernel modules: r8169
  1. I have this section:

    Section "Extensions"
        Option         "COMPOSITE" "Enable"
    EndSection
    

    in my /etc/X11/mhwd.d/nvidia.conf as well.

  2. What’s the output of:

    ls /sys/class/backlight
    

:question:

  1. That section is in there for me too, I think. It’s the second to last section

  2. In /sys/class/backlight there is a symlink to this acpi_video0 folder at /sys/devices/pci0000\:00/0000\:00\:01.0/0000\:01\:00.0/backlight/acpi_video0/, the contents of which are:

acpi_video0/actual_brightness:100
acpi_video0/bl_power:0
acpi_video0/brightness:100
grep: acpi_video0/device: Is a directory
acpi_video0/max_brightness:100
grep: acpi_video0/power: Is a directory
acpi_video0/scale:unknown
grep: acpi_video0/subsystem: Is a directory
acpi_video0/type:firmware

As I was meaning to say earlier, the value in the /sys/class/backlight/acpi_video0/brightness file (and the actual_brightness file) will change when I change my brightness via function keys or the sys tray slider, but my screen stays at 100% brightness. And I have a similar ideapad folder linked there after rebooting with the acpi_backlight=vendor Grub command-line option, with similar problems.

I have:

ls /sys/class/backlight/
nvidia_0

and it works!

What is:

mhwd --listinstalled
> Installed PCI configs:
--------------------------------------------------------------------------------
                  NAME               VERSION          FREEDRIVER           TYPE
--------------------------------------------------------------------------------
    video-nvidia-440xx            2019.10.25               false            PCI

(included my output to speed things up.)

:innocent:

Hello, i have the exact same problem here with a similar environment (same Lenovo Legion laptop + Nvidia + XFCE), similar configuration files (main difference is that i’m using kernel 5.4) and same content in /sys/class/backlight when using acpi_backlight=vendor.
Did you manage to fix it ?

Is there a way to rename the /sys/class/backlight/ideapad to nvidia_0 ?
I could not use mv or ln -s on it.

I notice a version mismatch between mhwd -li (which gives video-nvidia-440xx) and the driver i am supposed to be using (linux54-nvidia-450xx). Could it be related to the issue ?