Ideally the following command should work for any Xorg graphical session: Switching off the backlight (for example when one locks a notebook) can be useful to conserve battery energy. It also provides /usr/share/ddcutil/data/les and /usr/share/ddcutil/data/les for udev rules. If ddcutil is installed, it provides the /usr/share/ddcutil/data/nf file, which can be copied to /etc/X11// instead of manually editing Xorg configuration files.This can be achieved by adding a group i2c and configuring udev to set this group as the owner of the I2C devices. To facilitate binding screen brightness control to a keyboard shortcut, it may be convenient to enable non-superuser access to the relevant I2C devices.Dynamic Contrast Ratio or BenQ's Eye Care technology). ddcutil will fail to set some VCP features if there is a feature enabled on the monitor which already automatically adjusts them (e.g.Confirm that the settings are correctly applied with grep RegistryDwords /proc/driver/nvidia/params and check that the values are not empty.
#Monitor brightness drivers
Users of NVIDIA's proprietary drivers may need to add Option "RegistryDwords" "RMUseSwI2c=0x01 RMI2cSpeed=100" to the Device section in /etc/X11//nf (generated by nvidia-xconfig) or options nvidia NVreg_RegistryDwords=RMUseSwI2c=0x01 RMI2cSpeed=100 to /etc/modprobe/conf.d/nf.Using ddcci and i2c-dev simultaneously may result in resource conflicts such as a Device or resource busy error.Then, after loading the ddcci kernel module, one can use any backlight utility.
#Monitor brightness code
# ddcutil getvcp 10 VCP code 0x10 (Brightness ): current value = 60, max value = 100 # ddcutil setvcp 10 70Īlternatively, one may use ddcci-driver-linux-dkms AUR to expose external monitors in sysfs. # ddcutil capabilities | grep "Feature: 10" Feature: 10 (Brightness) The kernel module i2c-dev may need to be loaded if the /dev/i2c-* devices do not exist.ĭdcutil can be used to query and set brightness settings: Settings available via the OSD (On-Screen Display) panel can usually also be managed via DDC. DDC can control brightness, contrast, inputs, etc on supported monitors. When using this method, you need to use lspci first to find out where your graphic card is.ĭDC/CI (Display Data Channel Command Interface) can be used to communicate with external monitors implementing MCCS (Monitor Control Command Set) over I2C. Not all of the graphic cards support this method. It means you adjust the backlight by manipulating the hardware directly, which can be risky and generally is not a good idea. Intel Mobile 945GME ), it is possible to set the register of the graphic card to adjust the backlight. Tip: To set the backlight depending on power state, see Power management#Using a script and an udev rule and use your favourite backlight utility in the script. etc/udev/rules.d/les ACTION="add", SUBSYSTEM="backlight", RUN+="/bin/chgrp video $sys$devpath/brightness", RUN+="/bin/chmod g+w $sys$devpath/brightness" To allow users in the video group to change the brightness, a udev rule such as the following can be used: # echo 5 > /sys/class/backlight/acpi_video0/brightnessīy default, only root can change the brightness by this method. Attempting to set a brightness greater than the maximum results in an error. The brightness can be set by writing a number to brightness.
$ cat /sys/class/backlight/acpi_video0/max_brightness 15 The maximum brightness can be displayed by reading from max_brightness, which is often 15. $ ls /sys/class/backlight/acpi_video0/ actual_brightness brightness max_brightness subsystem/ uevent The directory contains the following files and subdirectories: If you use an Intel card, simply replace acpi_video0 with intel_backlight in the examples. In the following examples, acpi_video0 is used. In the case of an Intel card, the directory is called intel_backlight. In this case, the backlight is managed by an ATI graphics card. The name of the directory depends on the graphics card model. An interface to this module is provided via a sysfs(5) directory at /sys/class/backlight/. The power level can often be controlled using the ACPI kernel module for video. The brightness of the screen backlight is adjusted by setting the power level of the backlight LEDs or cathodes.
#Monitor brightness driver
6.8 Backlight is always at full brightness after a reboot with amdgpu driver.6.7 xbacklight returns : No outputs have backlight property.6.4 sysfs modified but no brightness change.6.3 Unable to control eDP Panel brightness (Intel i915 only).6.2 Inverted Brightness (Intel i915 only).6.1 Backlight PWM modulation frequency (Intel i915 only).
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