This page outlines steps that may be required to configure ddcutil after it has been installed.
Kernel Module i2c-dev
ddcutil requires kernel module i2c-dev. If it is not built into your kernel, it must be loaded explicly. To do so, add a file into directory /etc/modules-load.d with the single line:
As of release 1.4, ddcutil installation should automatically install this file, making manual configuration unnecessary.
For details, see Kernel Module Configuration.
I2C Device Permissions
Permissions must be granted in order for users other than root to run ddcutil.
As of release 2.0, ddcutil installation automatically installs files /usr/lib/udev/rules.d/60-ddcutil-i2c.rules and /usr/lib/udev/rules.d/60-usb.rules.
Using tag uaccess, these rules grant the logged on user read/write access to /dev/i2c devices associated with monitors.
For releases prior to 2.0, or if installing on a system that does not support udev (i.e. does not run systemd), manual configuration may be required. For details, see I2C Device Permissions.
Proprietary Nvidia Driver
The proprietary Nvidia video driver sometimes requires special settings for I2C communication. See Special Nvidia Driver Settings.
If ddcutil installs successfully but execution fails, command
can be used to probe the I2C environment and may provide clues as to the problem.
For USB connected monitors, use command
ddcutil usbenvironment. See Secondary Commands.
i2cdetect (found in required package i2ctools) provides an
independent check of whether the DDC slave address (X37) is active on an I2C bus.
Shared Library Configuration
When installing from source, additional configuration may be required to use shared library libddcutil if it is installed under /usr/local. See Shared Library Configuration. Note that libddcutil is NOT required to run ddcutil.
See also ddcutil Configuration.