Multiple users have reported building ddcutil for the Raspberry Pi and successfully running it. One user reported that the following settings were required in file /boot/config.txt in order to enable the I2C buses:
dtparam=i2c0=on dtparam=i2c1=on dtparam=i2c_vc=on dtparam=i2c_arm=on dtparam=i2c2_iknowwhatimdoing=yes
My own experiences are limited to a Raspberry Pi 3 Model B. Running Raspbian (Release 2017-09-07), the following single line is required in /boot/config.txt:
I could not find any other way to enable I2C for the HDMI connection, other than by using the vc4-kms-v3d driver.
Note that the only prebuilt ddcutil packages for the Raspberry Pi are those in Debian testing, which may be out of date. Generally speaking, ddcutil must be built from source for the Pi. .