ddcutil is a Linux program for querying and changing monitor settings,
such as brightness and color levels.

ddcutil primarily uses DDC/CI (Display Data Channel Command Interface)
to communicate with monitors implementing MCCS (Monitor Control Command
Set) over I2C. Normally, the video driver for the monitor exposes the
I2C channel as devices named /dev/i2c-n.

Use the following commands in order to be able to use ddcutil as a
regular user:

  # cp /usr/share/ddcutil/data/45-ddcutil-i2c.rules /etc/udev/rules.d
  # groupadd -r i2c
  # usermod -aG i2c your_username_here
