Debian 9: Backlight Brightness
Solution 1
Your system seems to have two interfaces for backlight control: backlight:acpi_video0
and backlight:radeon_bl0
. And apparently the ACPI interface does not work, and/or causes problems when used together with the Radeon-specific interface.
Since the Radeon-specific interface seems to work fine, I'd try telling systemd to stop using the ACPI backlight interface first:
systemctl mask systemd-backlight@backlight:acpi_video0.service
If necessary, this can be undone with:
systemctl unmask systemd-backlight@backlight:acpi_video0.service
If this does not help, further investigation is needed.
With journalctl -xb
you should be able to see a quite verbose version of messages for the current boot only. By default, persistent storage of systemd journal is not enabled in Debian 9, but it's quite easy to enable: just run mkdir /var/log/journal
as root. Then, starting from next boot, the journal will be stored persistently and you will be able to e.g. view the log of the previous boot from startup to shutdown with journalctl -xb -1
. The oldest logs will eventually be automatically purged, controlled by journald
's configurable criteria for available disk space.
Solution 2
Open file /etc/default/grub
and update the line:
GRUB_CMDLINE_LINUX_DEFAULT="quiet"
To line:
GRUB_CMDLINE_LINUX_DEFAULT="quiet acpi_backlight=video"
Then run:
update-grub
reboot
Possible alternative parameters case this one doesn't work (complete discussion at Kernel command-line options):
acpi_backlight=video
acpi_backlight=vendor
acpi_backlight=native
acpi_backlight=none
In my case, acpi_backlight=video
seems to have solved both issues:
- backlight brightness is no longer resetting to max during boot (question 1)
-
[Fn] + ←/→
was set as shortcut for decrease/increase backlight brightness (question 2)
After that there was a conflict with the shortcut [Fn] + ←
, which was decreasing the backlight brightness but also opening the Display Settings window. Just opened Preferences > Setup Hot Keys
and changed the 'obscure' Hotkey XF86Display
to something else.
Related videos on Youtube
Mark Messa
I have no special talent. I am only passionately curious.
Updated on September 18, 2022Comments
-
Mark Messa over 1 year
I've just installed a fresh new Debian 9 with LXDE into an ACER AMD Notebook and everything seems to be working fine, except for the backlight brightness. During the boot, it happens the following:
-
several messages and errors appear
[FAILED] Failed to start Load/Save Screen Backlight Brightness of backlight:acpi_video0. See 'systemctl status systemd-backlight@backlight:acpi_video0.service' for details. Starting Load/Save Screen Backlight Brightness of backlight:radeon_bl0 ... [ OK ] Started Load/Save Screen Backlight Brightness of backlight:radeon_bl0
often backlight brightness is reset to max
In order to set the backlight brightness to an acceptable level, the best solution so far seems to be opening a terminal and typing the command line below as soon as Debian initialize:
-
tee /sys/class/backlight/radeon_bl0/brightness <<< 15
Questions
- How to avoid the backlight brightness being reset to max during the boot?
- How to set shortcuts to the backlight brightness (ex:
[Fn] + ←/→
)?
Debug
root@debian:~# dmesg | grep -i "error\|firmware\|backlight" [ 1.049855] pci 0000:01:00.0: [Firmware Bug]: disabling VPD access (can't determine size of non-standard VPD format) [ 7.729996] EXT4-fs (sda1): re-mounted. Opts: errors=remount-ro [ 12.960474] radeon 0000:00:01.0: firmware: direct-loading firmware radeon/PALM_pfp.bin [ 13.017938] radeon 0000:00:01.0: firmware: direct-loading firmware radeon/PALM_me.bin [ 13.043827] radeon 0000:00:01.0: firmware: direct-loading firmware radeon/SUMO_rlc.bin [ 13.161157] radeon 0000:00:01.0: firmware: direct-loading firmware radeon/SUMO_uvd.bin [ 13.897112] [drm] radeon atom DIG backlight initialized
root@debian:~# systemctl status systemd-backlight@backlight:acpi_video0.service ● systemd-backlight@backlight:acpi_video0.service - Load/Save Screen Backlight Brightness of backlight:acpi_video0 Loaded: loaded (/lib/systemd/system/[email protected]; static; vendor preset: enabled) Active: failed (Result: exit-code) since Sat 2018-06-16 06:37:19 -03; 29min ago Docs: man:[email protected](8) Process: 411 ExecStart=/lib/systemd/systemd-backlight load backlight:acpi_video0 (code=exited, status=1/FAILURE) Main PID: 411 (code=exited, status=1/FAILURE) Jun 16 06:37:19 debian systemd[1]: Starting Load/Save Screen Backlight Brightness of backlight:acpi_video0... Jun 16 06:37:19 debian systemd[1]: systemd-backlight@backlight:acpi_video0.service: Main process exited, code=exited, status=1/FAILURE Jun 16 06:37:19 debian systemd[1]: Failed to start Load/Save Screen Backlight Brightness of backlight:acpi_video0. Jun 16 06:37:19 debian systemd[1]: systemd-backlight@backlight:acpi_video0.service: Unit entered failed state. Jun 16 06:37:19 debian systemd[1]: systemd-backlight@backlight:acpi_video0.service: Failed with result 'exit-code'.
Hardware Specifications
Notebook Aspire E1-421-0622 | product details- AMD 2 Core™ Processor E1-1200 (1.4 GHz) 1MB Cache 64-bit Processing
- AMD Radeon HD 7310 Graphics Controller
- 2Gb DDR3 SDRAM Memory
- 256MB shared video memory
Debian Strech
debian-9.4.0-amd64-netinst.iso- Small CDs
- AMD64 processor architecture
- Non-free package
firmware-amd-graphics
installed
radeon kernel modesetting for R600 or later requires firmware-amd-graphics - Software selection
( ) Debian desktop environment
( ) ... GNOME
( ) ... Xfce
( ) ... KDE
( ) ... Cinnamon
( ) ... MATE
(X) ... LXDE
( ) web server
(X) print server
( ) SSH server
(X) standard system utilities
-
-
Mark Messa almost 6 yearsI've also posted a partial solution. Let me know your comments.
-
Mark Messa almost 6 yearsJust tested
journalctl -xb
and, indeed, there is a lot of verbose in it. However, it is not in a 'friendly' manner compared to messages and errors. It seems awkward to me having to take a picture of the screen in order to capture the messages and errors during boot. -
Ombrophile almost 4 yearsIt is good if setting
acpi_backlight=video
worked, but this option means that acpi will use its default driver, ie,video.ko
[Ref.: kernel.org/doc/Documentation/admin-guide/kernel-parameters.txt]. As @telecoM rightly said, having bothacpi_video0
andradeon_bl0
in/sys/class/backlight
means that there are two interfaces for backlight control and one needs to be turned off. Since I too was facing the same issue, I went on withacpi_backlight=native
option to let only radeon control backlight. And sure enough the brightness reset issue was gone.