Apple Cinema Display Brightness Control

Compiling

Clone this repository:

git clone https://github.com/warvariuc/acdcontrol.git

Change to program directory and compile it:

cd acdcontrol
make

A new file acdcontrol should appear in the same directory. If compiling failed, check if you have installed packages necessary for compiling (e.g. build-essential).

Usage

./acdcontrol [--silent|-s] [--brief|-b] [--help|-h] [--about|-a] [--detect|-d] [--list-all|-l] <hid device(s)> [<brightness>]

NOTE: You must have write permissions to this device in order to control the display being a user, not root. If you have no such permissions, you can either grant read/write permission to the world:

sudo chmod a+rw /dev/usb/hiddevX

or change the ownership:

sudo chown <your user name>:users /dev/usb/hiddevX

NOTE: It should be safe to run the program on other device than Apple Cinema/Studio display as the program checks whether the device is Apple display and warns about it.

Parameters

-s, --silent

Suppress non-functional program output

-b, --brief

Print brightness value only when in query mode, otherwise ignored.

-h, --help

Show short help message and quit.

-a, --about

Show information about the program, some credits and thanks.

-d, --detect

Run program in the detection mode. In this mode no writes are performed to device so you can use any number of files if you are not sure that your monitor(s) are supported.

-l, --list-all

Lists all "officially" supported monitors and quits. If you do not see the device, this does not mean that it won't work it simply means that I did not tested it on such a device. I'll appreciate if you submit your information in the forum for any display that works hid device device that represents your Apple Cinema display. It should be one of /dev/usb/hiddevX or /dev/hiddevX.

brightness

When this option is specified, the operation is to set brightness, otherwise, the current brightness is retrieved. If brightness starts with + or -, the current brightness is increased or decreased by that value. (Note: You have to place -- before the negative value!)

Brightness is a parameter ranged [0-255]. Note, that not every value toggles the backlight power; different Apple Display models have different granularity. I use Apple Cinema 20" (clear plastic) and I'm feeling comfortable with the value of 160. I set 0, however, to see films in the darkness.

See also: --brief option and "Known Limitations" section.

Usage examples

In the following examples I assume that your HID device is /dev/hiddev0. You may have it as /dev/hiddevX or /dev/usb/hiddevX.

acdcontrol --help

Show long help message.

acdcontrol --detect /dev/hiddev*

Perform detection, which HID device is actually your display to be controlled.

acdcontrol /dev/hiddev0

Read current brightness parameter

acdcontrol /dev/hiddev0 160

Set brightness to 160. Note, that brightness setting depends on your model. Generally, this parameter may get values in the range [0-255].

acdcontrol /dev/hiddev0 +10

Increment current brightness by 10.

acdcontrol /dev/hiddev0 -- -10

Decrement current brightness by 10. Please,note --!

Known Limitations

Currently, the display detection process is not fully automated as you need to specify a HID device path.

First time (after boot up) brightness is retrieved incorrectly (zero value), however, after it is set, the return value is correct. It shouldn't concern you much as Cinema/Studio Display stores actual brightness settings between the sessions.