`keyboard-backlightd`

[ [crates.io] ] [ [lib.rs] ] [ [AUR] ]

A daemon to turn off the keyboard backlight when idle.

Features:

Small, minimal dependencies, fast to compile.
Supports adjusting the keyboard backlight using the normal key (by monitoring if brightness was changed by hardware and adjusting accordingly).

Limitations:

Only tested on modern ThinkPads.
Very little auto-detection, you will need to configure your input devices
Linux only. Uses some very low level APIs.

Installation

While this package can be built with cargo as most rust packages, it uses make for installation. This is because cargo is not able to install the additional files that are needed: The config file and the systemd unit file.

Why is this needed? Since this is a system daemon it needs to be installed system-wide and run as root (to be able to access certain files in /dev and /sys).

Thus you should ideally install this with your distro package manager. A package for Arch Linux is available on [AUR] (maintained by the author of this package).

If you do not use Arch Linux, I would appreciate if you can contribute creating a package! However, if you do not want to create a package, do something like this to install into /usr/local:

console $ # NOTE! Not recommended! This will overwrite your config file for this $ # program, which sucks if you customised it. Use your package manager $ # instead! $ make $ sudo make install

Warning!

This program will monitor your key presses, but only to detect when you press the keys. It does however not care about what you press. The only thing the code checks is if it is a LED changing state, in which case it is ignored (otherwise, pressing Caps Lock on an external keyboard would light up the keyboard backlight).

In summary: This code works very similar to how a keylogger would, except that it is benign. But you should read the code first to make sure you trust me with this! (This is a good idea in general!)

The code that does this is in handlers.rs in the mod ev_dev section.

Figuring out input devices & LEDs

You probably want this daemon to turn on the keyboard backlight on any of:

Keyboard keys
Special Fn-key combos?
Touchpad
Trackpoint

The easiest way is to run sudo evtest (you may need to install a package such as evtest). This will give you an output such as this:

console $ sudo evtest No device specified, trying to scan all of /dev/input/event* Available devices: /dev/input/event0: Sleep Button /dev/input/event1: Lid Switch /dev/input/event10: ThinkPad Extra Buttons /dev/input/event11: HDA Intel PCH Mic /dev/input/event12: HDA Intel PCH Headphone /dev/input/event13: HDA Intel PCH HDMI/DP,pcm=3 /dev/input/event14: HDA Intel PCH HDMI/DP,pcm=7 /dev/input/event15: HDA Intel PCH HDMI/DP,pcm=8 /dev/input/event16: Synaptics TM3276-022 /dev/input/event17: TPPS/2 IBM TrackPoint /dev/input/event18: Integrated Camera: Integrated C /dev/input/event19: MX Vertical Mouse /dev/input/event2: Power Button /dev/input/event3: AT Translated Set 2 keyboard /dev/input/event4: Video Bus /dev/input/event5: Video Bus /dev/input/event6: Microsoft Comfort Curve Keyboard 3000 /dev/input/event7: Microsoft Comfort Curve Keyboard 3000 /dev/input/event8: Raydium Corporation Raydium Touch System /dev/input/event9: PC Speaker Select the device event number [0-19]:

This lets you identify the input devices Linux sees. However, this is not quite what you want, as the numbering is not guaranteed to be stable across reboots.

Next you need to find a stable ID for these:

console $ ls -l /dev/input/by-id lrwxrwxrwx 1 root root 9 7 feb 16.31 usb-Microsoft_Comfort_Curve_Keyboard_3000-event-kbd -> ../event6 lrwxrwxrwx 1 root root 9 7 feb 16.31 usb-Microsoft_Comfort_Curve_Keyboard_3000-if01-event-kbd -> ../event7 lrwxrwxrwx 1 root root 9 7 feb 16.31 usb-Raydium_Corporation_Raydium_Touch_System-event-if00 -> ../event8 lrwxrwxrwx 1 root root 10 7 feb 16.31 usb-SunplusIT_Inc_Integrated_Camera-event-if00 -> ../event18 $ ls -l /dev/input/by-path lrwxrwxrwx 1 root root 9 7 feb 16.31 pci-0000:00:14.0-usb-0:10:1.0-event -> ../event8 lrwxrwxrwx 1 root root 9 7 feb 16.31 pci-0000:00:14.0-usb-0:1:1.0-event-kbd -> ../event6 lrwxrwxrwx 1 root root 9 7 feb 16.31 pci-0000:00:14.0-usb-0:1:1.1-event-kbd -> ../event7 lrwxrwxrwx 1 root root 10 7 feb 16.31 pci-0000:00:14.0-usb-0:8:1.0-event -> ../event18 lrwxrwxrwx 1 root root 10 7 feb 16.31 pci-0000:00:1f.4-event-mouse -> ../event16 lrwxrwxrwx 1 root root 9 7 feb 16.31 pci-0000:00:1f.4-mouse -> ../mouse1 lrwxrwxrwx 1 root root 10 7 feb 16.31 pci-0000:00:1f.4-serio-2-event-mouse -> ../event17 lrwxrwxrwx 1 root root 9 7 feb 16.31 pci-0000:00:1f.4-serio-2-mouse -> ../mouse2 lrwxrwxrwx 1 root root 9 7 feb 16.31 platform-i8042-serio-0-event-kbd -> ../event3 lrwxrwxrwx 1 root root 9 7 feb 16.31 platform-pcspkr-event-spkr -> ../event9 lrwxrwxrwx 1 root root 10 7 feb 16.31 platform-thinkpad_acpi-event -> ../event10

Here you should prefer a by-id mapping if one exists for your device, though for non-USB devices by-path will likely work fine.

From the output above we can conclude that we want:

| Device | Human readable name | Number | Path we want | |-----------------|------------------------------------------|--------|----------------------------------------------------------------------------| | Keyboard | AT Translated Set 2 keyboard | 3 | /dev/input/by-path/platform-i8042-serio-0-event-kbd | | Special buttons | ThinkPad Extra Buttons | 10 | /dev/input/by-path/platform-thinkpad_acpi-event | | Touchpad | Synaptics TM3276-022 | 16 | /dev/input/by-path/pci-0000:00:1f.4-event-mouse | | Trackpoint | TPPS/2 IBM TrackPoint | 17 | /dev/input/by-path/pci-0000:00:1f.4-serio-2-event-mouse | | Touchscreen | Raydium Corporation Raydium Touch System | 8 | /dev/input/by-id/usb-Raydium_Corporation_Raydium_Touch_System-event-if00 |

These are (for this laptop, a ThinkPad T480) all the inputs we want to monitor.

Here are some hints for figuring this out:

The two most common vendors I have seen for touchpads are Synaptics and ALPS.
You can always use evtest to check if key presses go to a specific device.

Thus, our command line for keyboard-backlightd would look like:

-i /dev/input/by-path/platform-i8042-serio-0-event-kbd \ -i /dev/input/by-path/platform-thinkpad_acpi-event \ -i /dev/input/by-path/pci-0000:00:1f.4-event-mouse \ -i /dev/input/by-path/pci-0000:00:1f.4-serio-2-event-mouse \ -i /dev/input/by-id/usb-Raydium_Corporation_Raydium_Touch_System-event-if00

Then you also need to figure out the path to your LED for keyboard backlight. This is thankfully much easier:

console $ ls -d /sys/class/leds/*kbd* /sys/class/leds/tpacpi::kbd_backlight

In this case there was only one option. This means we want:

-l /sys/class/leds/tpacpi::kbd_backlight

Minimum supported rust version (MSRV)

YMMV. It works on rustc 1.67.0 as of writing. It should continue working on the latest stable Rust. I will not test on older versions than whatever happens to be the latest stable when I make a change.

So in summary: There is no MSRV policy.

License

keyboard-backlightd is released under GPL 3.0 (only, not "or later").