ddccontrol - change display input
In my DKVM setup, I always use my 2nd graphicscard for my guests. Sadly my monitor does not have automatic input detection, so a little trickery is needed to switch input.
For my DKVM host OS, I use the DVI input.
For my VM guests, I use the DisplayPort input.
ddccontrol - probing
ddccontrol -p is used for probing the I2C bus for displays.
To find the information needed, first find the I2C bus for the display - it should look similar to this
In my case, my monitor is in dev:/dev/i2c-17
Finding the needed i2c address and values.
Still looking at the output from "ddccontrol -p", find a section like "Input settings"
In my case, the i2c address for setting inputsource is 0x60, and the accepted values are
15: DisplayPort
3: DVI
4: HDMI
1: VGA
Writing to the i2c address
To set another display input, use the information gathered, and use "-w" to write
example : ddccontrol -r 0x60 -w 15 dev:/dev/i2c-17
This will set the input source to DisplayPort
Wrapping it up
In my case, I need to set the input to DisplayPort when my Linux guest is starting, and set it back to DVI when I am done.
While there are plenty of ways to run scripts in startup/shutdown, I opted for the easy solution - and just went with an old-fashioned OpenRC init style script, and placed symlinks to the different rc levels.
/etc/init.d/ddccontrol
And the required symlinks
#!/bin/sh
case "$1" in
start)
/usr/bin/ddccontrol -r 0x60 -w 15 dev:/dev/i2c-17
;;
stop)
/usr/bin/ddccontrol -r 0x60 -w 3 dev:/dev/i2c-17
esac
And the required symlinks
#!/bin/sh
$ find /etc -iname "*ddccontrol" -exec ls -l {} \; 2>/dev/null
lrwxrwxrwx 1 root root 20 Jul 23 12:49 /etc/rc6.d/K99ddccontrol -> ../init.d/ddccontrol
lrwxrwxrwx 1 root root 20 Jul 23 12:52 /etc/rc0.d/K99ddccontrol -> ../init.d/ddccontrol
lrwxrwxrwx 1 root root 20 Jul 23 12:49 /etc/rc3.d/S01ddccontrol -> ../init.d/ddccontrol
-rwxr-xr-x 1 root root 148 Jul 23 12:48 /etc/init.d/ddccontrol
