ddcutil 1.2.2 Control external monitor settings
ddcutil can query and modify most external monitors' settings, such as brightness, colour levels, and input sources. Generally speaking, any setting that can be changed by pressing buttons on the monitor can be modified by ddcutil.
ddcutil communicates directly with monitors implementing the Monitor Control Command Set (MCCS). It usually does so through the the Display Data Channel Command Interface (DDC/CI) protocol on the I2C bus, but can also communicate over USB as per the USB Monitor Control Class Specification.
One particular use case is in colour profile management. Monitor calibration is relative to the monitor colour settings currently in effect, e.g. red gain. ddcutil allows colour-related settings to be saved at the time a monitor is calibrated, and restored when the calibration is applied.