DDC/CI control

DDCcontrol is a software used to control monitor parameters, like brightness, contrast, RGB color levels and others.

DDCcontrol consists of:

• ddccontrol - command-line tool for monitor parameters control
• gddccontrol - GUI tool for monitor parameters control

DDCcontrol communicates with monitors from userspace through the Linux i2c-dev interface (/dev/i2c-*). AMD ADL and legacy direct PCI backends have been removed. For directly connected displays, this uses the same kernel userspace I2C path as ddcutil; USB-connected DDC/CI displays are not supported yet.

Installation

The most convenient way to install DDCcontrol is to use packages from official distribution repositories.

Manual installation is more complicated, but contains latest version of software and more monitor profiles.

Installation from official packages

DDCcontrol tools, ddccontrol and gddccontrol can be installed from official distribution repositories with following command:

• on Ubuntu/Debian: sudo apt install ddccontrol gddccontrol ddccontrol-db i2c-tools
• on Fedora: sudo dnf install ddccontrol ddccontrol-gtk
• on openSUSE: sudo zypper in ddccontrol i2c-tools

You might need to restart your system after installing i2c-tools.

Installation from sources

Install build dependencies:

• on Ubuntu: sudo apt install intltool i2c-tools libxml2-dev libgtk3.0-dev liblzma-dev
• on Solus: sudo eopkg install -c system.devel
sudo eopkg install autoconf automake intltool i2c-tools m4 diffutils libtool-devel xz-devel libxml2-devel libgtk-3-devel
• on others: install autotools, intltool, i2c-tools, libxml2 development files, GTK 3 development files and xz/lzma development files using your distribution's package manager.

Clone, build and install built version:

git clone https://github.com/ddccontrol/ddccontrol.git
cd ddccontrol
./autogen.sh
./configure --prefix=/usr/local/ --sysconfdir=/etc --libexecdir=/usr/local/lib
make
sudo make install

Monitor database is required for proper functionality. See for ddccontrol-db installation.

Contributing to the Monitor Database

Follow the instructions on https://github.com/ddccontrol/ddccontrol-db/blob/master/doc/how-to-add-a-monitor.md for inclusion. It often merely involves adapting a few standard capabilities as many pull requests show.

Usage

From GUI using gddccontrol

gddccontrol is a graphical utility for monitor configuration. It is called Monitor Settings in list of applications.

DDCcontrol needs readable and writable /dev/i2c-* devices. Most distributions provide this through the i2c-dev kernel module and an i2c group. Following configuration is needed to allow a non-root user to use gddccontrol:

sudo adduser $USER i2c
sudo /bin/sh -c 'echo i2c-dev >> /etc/modules'

Utility can launched directly from commandline:

sudo gddccontrol

gddccontrol uses standard GTK3 widgets and follows the configured GTK theme. To try the GTK high-contrast dark theme for one launch, run:

GTK_THEME=HighContrastInverse gddccontrol

If you need to run gddccontrol through sudo, preserve the theme override with env:

sudo env GTK_THEME=HighContrastInverse gddccontrol

For GNOME Shell top-bar menu control, see the example extension in contrib/gnome-shell-extension.

From command line using ddccontrol

ddccontrol allows monitor configuration directly from commandline. To probe I2C devices to find monitor buses use:

sudo ddccontrol -p

To read value of control 0x10 (brightness on VESA compliant monitors) for device dev:/dev/i2c-4:

sudo ddccontrol -r 0x10 dev:/dev/i2c-4

To set value of control 0x10 (brightness on VESA compliant monitors) to 75 for device dev:/dev/i2c-4:

sudo ddccontrol -r 0x10 -w 75 dev:/dev/i2c-4

# Save current monitor settings to non-volatile memory (if supported)
sudo ddccontrol -r 0x10 -w 75 -s dev:/dev/i2c-4

See ddccontrol -h for more information.

Troubleshooting

NVIDIA proprietary driver — I2C/DDC not working over DisplayPort or HDMI

The NVIDIA proprietary driver sometimes fails to expose /dev/i2c-* devices for DDC/CI communication, causing ddccontrol -p to find no monitors (or to return I2C errors) when connected via DisplayPort or HDMI.

The fix is to add an Xorg configuration snippet that enables software I2C in the NVIDIA driver. A ready-made configuration file is shipped with DDCcontrol at $(datadir)/ddccontrol/90-nvidia-i2c.conf (typically /usr/share/ddccontrol/90-nvidia-i2c.conf after installation). Copy it into place and restart your X session:

sudo cp /usr/share/ddccontrol/90-nvidia-i2c.conf /etc/X11/xorg.conf.d/

If you built from source without installing, you can copy the file directly from the source tree:

sudo cp data/90-nvidia-i2c.conf /etc/X11/xorg.conf.d/

After restarting X, ddccontrol -p should detect your monitors normally.

See the NVIDIA developer forum thread for background on this issue.

License

The project is licensed under GNU General Public License v2.0 license. See COPYING for details.