Contrôler la puissance du rétro-éclairage de votre écran d’ordinateur.
Almost all computer screens made in the last decade support DDC/CI. (The Display Data Channel Command Interface).
You can use it to control stuff like the backlight brightness without fiddling with the awful screen buttons and OSD.
On Linux once you load the ddcci kernel module the screens appear in /sys/class/backlights and can be controlled like a laptop screen.
With Artix Linux on a DELL XPS 9710 laptop the module was not found, but not needed.
$ sudo pacman -Ss brightnessctl (1)
galaxy/brightnessctl 0.5.1-2.2
Lightweight brightness control tool
$ sudo pacman -S brightnessctl (2)
[…]
:: Traitement des changements du paquet…
(1/1) installation de brightnessctl [###############################] 100%
:: Exécution des crochets (« hooks ») de post-transaction…
(1/1) Reloading device manager configuration...| 1 | Search for the paquet brightnessctl |
| 2 | Installation of the paquet (only the end of the log is reproduced here) |
$ sudo brightnessctl --list (1)
Available devices:
Device 'intel_backlight' of class 'backlight': (2)
Current brightness: 102 (20%) (3)
Max brightness: 512 (4)
Device 'phy0-led' of class 'leds': (5)
Current brightness: 1 (100%) (6)
Max brightness: 1 (7)
Device 'input3::numlock' of class 'leds':
Current brightness: 0 (0%)
Max brightness: 1
Device 'input3::capslock' of class 'leds': (8)
Current brightness: 0 (0%) (9)
Max brightness: 1
Device 'input3::scrolllock' of class 'leds':
Current brightness: 0 (0%)
Max brightness: 1
Device 'dell::kbd_backlight' of class 'leds':
Current brightness: 0 (0%)
Max brightness: 2 (10)| 1 | List all available devices and controls |
| 2 | This line starts a device section in the output and its the screen backlight |
| 3 | This is the current state of the device |
| 4 | This indicates the maximum integer value that can be set |
| 5 | Here we can control a single led (somewhere else, and I don’t where to be true) |
| 6 | It is reported as turned on |
| 7 | It can only be off (0) or on (1) |
| 8 | Here we have the led that shows the capslock keyboard state |
| 9 | It is reported as off (and I can verify it) |
| 10 | Here we can see that the keyboard backlight has 2 possible levels (and it’s true) |
$ sudo brightnessctl --device 'input3::capslock' s 1 (1)
Updated device 'input3::capslock':
Device 'input3::capslock' of class 'leds':
Current brightness: 1 (100%) (2)
Max brightness: 1| 1 | Here I set to 1 the capslock led state |
| 2 | So it’s now reported as "on" and I confirm it (despite the funny fact that letters are still minus typed) |
We can notice that for this computer, we can’t get the webcam led lying like the capslock one.
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