Configure `/dev/i2c-*` devices
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## Configure `/dev/i2c-*` devices

DDCcontrol only uses userspace I2C access through `/dev/i2c-*` devices. Legacy direct PCI memory access and AMD ADL support have been removed, and USB-connected DDC/CI displays are not supported yet.

The kernel graphics driver must expose the monitor DDC bus as an I2C adapter, and the `i2c-dev` module must be loaded. To load it manually, type as root:

    # modprobe i2c-dev

If you want to automatically load this module when Linux starts, see your distribution's documentation. DDCcontrol also installs a `modules-load.d` configuration file for this purpose on systems that use systemd.

To allow standard (i.e. non-root) users to use DDCcontrol, grant read and write access to the relevant `/dev/i2c-*` devices. Many distributions do this with an `i2c` group, for example by adding your user to that group. For quick local testing, this can also be done by typing as root:

    # chgrp i2c /dev/i2c-*
    # chmod g+rw /dev/i2c-*

### Kernel configuration options

If `i2c-dev` or the relevant graphics driver support is not available with your kernel, you can build your own kernel with the following options turned on (we recommend building them as modules):

- Devices drivers → I2C support.
- Devices drivers → I2C support → I2C device interface.
- Devices drivers → Graphics support → Direct Rendering Manager.
- and a specific driver for your graphics card.

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