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I've set up a Samsung 90X3A from scratch (using BIOS boot to avoid a known related issue), and I'm having trouble enabling the screen brightness keys (Fn+F2 and Fn+F3).

The current state:

  • Manually setting the brightness works:

    sudo tee /sys/class/backlight/intel_backlight/brightness <<< 1000
sudo tee /sys/class/backlight/acpi_video0/brightness <<< 50

  • xbacklight works:

    $ xbacklight -get
100.000000

  • Fn+F2 and Fn+F3 are detected properly:

    $ sudo evtest /dev/input/event0
  Input driver version is 1.0.1
Input device ID: bus 0x11 vendor 0x1 product 0x1 version 0xab41
Input device name: "AT Translated Set 2 keyboard"
Supported events:
[…]
Event code 224 (KEY_BRIGHTNESSDOWN)
Event code 225 (KEY_BRIGHTNESSUP)
[…]
Event: time […], type 4 (EV_MSC), code 4 (MSC_SCAN), value 89
Event: time […], type 1 (EV_KEY), code 224 (KEY_BRIGHTNESSDOWN), value 1
Event: time […], -------------- SYN_REPORT ------------
Event: time […], type 4 (EV_MSC), code 4 (MSC_SCAN), value 89
Event: time […], type 1 (EV_KEY), code 224 (KEY_BRIGHTNESSDOWN), value 0
Event: time […], -------------- SYN_REPORT ------------
Event: time […], type 4 (EV_MSC), code 4 (MSC_SCAN), value 88
Event: time […], type 1 (EV_KEY), code 225 (KEY_BRIGHTNESSUP), value 1
Event: time […], -------------- SYN_REPORT ------------
Event: time […], type 4 (EV_MSC), code 4 (MSC_SCAN), value 88
Event: time […], type 1 (EV_KEY), code 225 (KEY_BRIGHTNESSUP), value 0
Event: time […], -------------- SYN_REPORT ------------

  • ACPId is running:

    $ systemctl is-active acpid
active

  • xmodmap doesn't agree with evtest (but see below for attempted workaround):

    $ xmodmap -pke | egrep '224|225'
keycode 224 = XF86Messenger NoSymbol XF86Messenger
keycode 225 = XF86Search NoSymbol XF86Search

However, the screen brightness does not change.

There are heaps of advice around for dealing with this and similar issues. Here's what I've already tried:

Other possibly relevant system information:

  • X process tree:

    $ ps af -e --format user,cmd | sed "s/$USER/user  /g"
USER     CMD
[…]
root     /usr/bin/lightdm
root      \_ /usr/lib/xorg-server/Xorg :0 -seat seat0 -auth /run/lightdm/root/:0 -nolisten tcp vt7 -novtswitch
root      \_ lightdm --session-child 13 20
user          \_ awesome
user              \_ logger --priority user notice --tag xprofile-user
user              \_ logger --priority user error --tag xprofile-user
user              \_ xss-lock slock
user              \_ cbatticon
Community
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l0b0
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  • Only one `acpi_video0` xor `intel_backlight` should be able to set the brightness, not both. You should then be able to add something like `Option "Backlight" "intel_backlight"` (or acpi) to xorg.conf. I suspect that xorg is using the one that does not work. – grochmal Oct 08 '16 at 22:58
  • *Both* of them work, as does xbacklight, even after adding the backlight option to `/etc/X11/xorg.conf`. And no warnings or errors in `/var/log/Xorg.0.log`. So that doesn't seem right. – l0b0 Oct 08 '16 at 23:49
  • Hmm... it is the first time I see two /sys controls working. Random guessing now: `xmodmap -pke | egrep '224|225'`? and whether [this works](https://aur.archlinux.org/packages/light/)? (it is what I use, and the author is currently implementing the keyboard usage, look in the github issues for that) – grochmal Oct 09 '16 at 00:17
  • `keycode 224 = XF86Messenger NoSymbol XF86Messenger`, `keycode 225 = XF86Search NoSymbol XF86Search` – l0b0 Oct 09 '16 at 00:39
  • Wow! That doesn't seem right. It seems to contradict your `evtest`. My guess is that `xmodmap -e 'keycode 224 = XF86MonBrightnessDown NoSymbol XF86MonBrightnessDown'` and `xmodmap -e 'keycode 225 = XF86MonBrightnessUp NoSymbol XF86MonBrightnessUp'` have a good chance of making the keys work as they should. – grochmal Oct 09 '16 at 00:56
  • Nope. And I double checked the output of both `xmodmap` and `evtest` before running them. – l0b0 Oct 09 '16 at 08:27
  • Hmm... I'm clueless. I would try to use my WM's keybindings to get the functionality through `xbacklight -set`. But i use Xmonad, so it is easy for me. I believe i3 has similar functionality but not so sure about other WMs. – grochmal Oct 09 '16 at 17:46

1 Answers1

2

For now I'm working around this by hardcoding commands to handle the XF86 events in Awesome WM:

awful.key({}, "XF86MonBrightnessDown", function () awful.util.spawn_with_shell("xbacklight -dec 5") end),
awful.key({}, "XF86MonBrightnessUp", function () awful.util.spawn_with_shell("xbacklight -inc 5") end),

I'm still holding out for a solution to handle this independently of the window manager.

l0b0
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  • You will need *some* program to process the keys, so you might as well use the window manager that's already running ... or why do you prefer a different program that you'd have to run additionally? – dirkt Oct 10 '16 at 09:17
  • I would expect the OS to handle this without *any* manual configuration. – l0b0 Oct 10 '16 at 09:34
  • The *OS* doesn't handle it at all (and why should it? Linux runs fine without any sort of graphics display or keyboard). Some *desktop environments* handle it by running additional programs (without any manual configuration, in most cases), but you don't seem to have those installed. – dirkt Oct 10 '16 at 10:41
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    I don't have to implement my own boot loader. I don't have to set up my own compose key table. I don't have to create a colour scheme for `top`. And I *should not* have to bind extremely common keyboard shortcuts to commands. I would *definitely* expect this to be part of a very minimal working X desktop system. – l0b0 Oct 10 '16 at 17:29
  • Well, it *is* part of the bigger desktop systems. But if you don't run these, but use your own choice of window manager instead (which I do, too), and nobody wrote that part for that particular window manager (which is some effort, because there's lots of variations concerning backlight handling), then it's not there. And running an *additional* program that may conflict with the WM isn't the solution. :-) It's open source, contact the maintainers of Awesome WM and suggest to include it in the standard configuration. Which they probably won't do, because `xbacklight` doesn't work everywhere. – dirkt Oct 10 '16 at 18:26