Do I need to do something special to get DDC/CI to work over DisplayPort

displaydisplayportgraphics card

My monitor is a Dell P2715Q, and it does support DDC/CI (presumably). It's connected to my computer with a DisplayPort, and I'm trying to change the brightness from my computer, but it neither works on Windows nor Ubuntu.

I'm using Intel HD 530 integrated graphics, and supposedly, the drivers should support DDC/CI over DisplayPort. The "DDC/CI" option in the monitor's OSD is set to "enabled".

When I try to change the brightness on either Windows or Ubuntu, there is no option to do so where it would normally be. On Linux, I'm also testing with a program called ddccontrol, and when I run ddccontrol -p, it says: "No monitor supporting DDC/CI available".

Best Answer

On Linux, the first order answer is that it should just work. The I2C signals are carried over the DisplayPort AUX channel, and the video driver should make this transparent.

ddccontrol can be problematic because, as normally built (there's a lot of #iftested code) it bypasses the public i2c-dev interface and attempts to control the I2C signals directly.

I suggest you try my more recent ddcutil.
There are lots of features, but the following should get you started:

# To display detected monitors:
ddcutil detect 

# To get the current brightness value (assuming just 1 monitor):
ddcutil getvcp 10

# To set the brightness to an example value of 50:
ddcutil setvcp 10 50

That said, I can't speak to the HD 530 specifically. If it uses the standard Linux i915 driver then it should work.

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