Backlight: Difference between revisions
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Backlight control of liquid-crystal displays (LCDs) screen is covered in this page. | Backlight control of liquid-crystal displays (LCDs) screen is covered in this page. Controlling display backlight requires either the proper udev rules, or using some form of privilege escalation. | ||
{{Pkg|brightnessctl}} is one popular | There are multiple utilities available for this purpose. | ||
== Brightnessctl == | |||
The command <Code>brightnessctl</Code> from {{Pkg|brightnessctl}} package is one popular and reliable alternative, although its default udev rules require too wide permissions (see {{Issue|15409}}). You may need your own rules, or configure doas to allow running it as an unprivileged user. | |||
Optionally enable brightnessctl service to restore brightness settings on reboot:{{Cmd|# rc-update add brightnessctl}} | |||
When used with {{Pkg|ddcci-driver-linux-src}} package, brightnessctl can also be used to control external Monitor. This requires | |||
== Ddcutil == | == Ddcutil == | ||
The command <Code>ddcutil</Code> from the package {{Pkg|ddcutil}} can be used to control brightness in external monitors, if your hardware supports it. | The command <Code>ddcutil</Code> from the package {{Pkg|ddcutil}} can be used to control brightness in external monitors, if your hardware supports it. | ||
Once the package is installed, check the current brightness of your monitor by issuing the command {{Cmd|ddcutil -d 1 getvcp 10}} | Once the package is installed, check the current brightness of your monitor by issuing the command {{Cmd|ddcutil -d 1 getvcp 10}} | ||
Revision as of 05:35, 18 December 2024
Backlight control of liquid-crystal displays (LCDs) screen is covered in this page. Controlling display backlight requires either the proper udev rules, or using some form of privilege escalation.
There are multiple utilities available for this purpose.
Brightnessctl
The command brightnessctl from brightnessctl package is one popular and reliable alternative, although its default udev rules require too wide permissions (see #15409). You may need your own rules, or configure doas to allow running it as an unprivileged user.
Optionally enable brightnessctl service to restore brightness settings on reboot:
# rc-update add brightnessctl
When used with ddcci-driver-linux-src package, brightnessctl can also be used to control external Monitor. This requires
Ddcutil
The command ddcutil from the package ddcutil can be used to control brightness in external monitors, if your hardware supports it.
Once the package is installed, check the current brightness of your monitor by issuing the command
ddcutil -d 1 getvcp 10
To set brightness of your monitor to 50% issue the command:
ddcutil -d 1 setvcp 10 50
Troubleshooting
No /dev/i2c devices exist
The command ddcutil may generate the below error:
Unexpected error. Unable to open sysfs directory /sys/class/drm/card1-HDMI-A-1/ddc/i2c-dev: No such file or directory Unexpected error. Unable to open sysfs directory /sys/class/drm/card1-HDMI-A-2/ddc/i2c-dev: No such file or directory No /dev/i2c devices exist. ddcutil requires module i2c-dev.
If you receive the above error, on running ddcutil, then load the i2c-dev kernel module:
# modprobe i2c-dev
Rebooting the computer after installing ddcutil should automatically load the above module based on /usr/lib/modules-load.d/ddcutil.conf.