# External LCD backlight control



## JohnnySorocil (Oct 27, 2019)

Is it possible to control backlight of external monitor connected with DisplayPort with FreeBSD?
As far I understood commands are sent over DDC protocol (similar to I2C). But there are no ddcutil/ddccontrol tools for FreeBSD.

I am not interested in changing color temperature via xbacklight/redlight/sct.
Internal LCD of my ThinkPad T430s (FHD mod + CoreBoot if that is relevant) can be controlled with:
get levels:

```
% sysctl hw.acpi.video.lcd0.levels
hw.acpi.video.lcd0.levels: 100 100 2 4 5 7 9 11 13 18 20 24 29 33 40 50 67 100
```
change brightness

```
% sysctl hw.acpi.video.lcd0.brightness=20
hw.acpi.video.lcd0.brightness: 29 -> 20
```
acpi_ibm and acpi_video kernel modules are loaded.


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