ThinkPad's keyboard backlight control

[aragats]

How to turn on keyboard backlight programmatically?
Echoing 0 to /dev/led/thinklight turns it off, as well as sysctl dev.acpi_ibm.0.thinklight=0, but I couldn't find a way to turn it on.
Thanks for ideas!

 

[SirDice]

Maybe a shot in the dark, but echo'ing a '1' instead of a '0'?

 

[aragats]

Maybe a shot in the dark, but echo'ing a '1' instead of a '0'?

That's the first thing I tried. Has no effect with the device node, and:

# sysctl dev.acpi_ibm.0.thinklight=1
dev.acpi_ibm.0.thinklight: 0 -> 0

 

[SirDice]

The sysctl(8) is more of a indicator to query, is it on or off? I actually expected this to be read-only from the man page's description.

     dev.acpi_ibm.0.thinklight
             Indicates, whether the ThinkLight keyboard light is activated or
             not.

acpi_ibm(4)

The led(4) device however:

     State can be set directly, and since the change happens immediately, it
     is possible to flash the annunciator with very short periods and
     synchronize it with program events.  It should be noted that there is a
     non-trivial overhead, so this may not be usable for benchmarking or
     measuring short intervals.

           0       Turn the annunciator off immediately.
           1       Turn the annunciator on immediately.

So echo 1 > /dev/led/thinklight?

 

[fraxamo]

but I couldn't find a way to turn it on

Can you try sysctl dev.acpi_ibm.0.thinklight=255? More information at this link.

 

[snakedoctr]

Is it the Thinklight you want to turn on, or the keyboard backlight? The Thinklight was an actual LED at the top of the display on older Thinkpads (https://en.wikipedia.org/wiki/ThinkLight). I haven't found a way to turn the actual keyboard backlight on/off outside of using the Fn+Space combo keys.

 

[aragats]

So echo 1 > /dev/led/thinklight?

Has no effect.
Interesting observation: echoing any number which starts with 1 is silently accepted with no effect. Any other number causes "Invalid argument" error.

Can you try sysctl dev.acpi_ibm.0.thinklight=255? More information at this link.

"Invalid argument"

The Thinklight was an actual LED at the top of the display on older Thinkpads.

That's indeed confusing. I have had such ThinkPads with an LED. In those laptops I was able to control various LEDs, like Ethernet's, power etc.
Now if I can turn the backlight off by echoing 0, there must be a way to turn it on!

 

[bda65]

With my previous laptop (asus zenbook) the backlight of the keyboard needed two echo 1 > /dev/led/xxx before turning on.
Maybe...

 

[blackbird9]

/usr/bin/backlight works for me. You can say 'backlight incr 5' to raise the level 5%, or 'backlight decr 5' to lower the level 5%.

You have to 'kldload acpi_ibm' first (add 'acpi_ibm_load="YES"' to /boot/loader.conf).

 

[T-Aoki]

The old review trying to introduced the feature was D14103.

 

[aragats]

'backlight incr 5' to raise the level 5%

That's for display backlight, not keyboard...
(I have a script for that which also "linearizes" the increments for visual perception)

 

[blackbird9]

Oh dear, I should have read more carefully