# command line to switch off back light of an USB keyboard

## toralf

I do wonder if I do have a chance to switch off the back light of my "VENDOM Illuminated Scissor Keyboard, black" somehow in /proc or /sys ?

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## fedeliallalinea

Can help this?

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## toralf

 *fedeliallalinea wrote:*   

> Can help this?

 Not really, I can set and get values between 0 and 2 but the keyboard back light itself doesn't change

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## fedeliallalinea

In /sys/class/leds/ you have some entry referencing on keyboard backlight?

In my system (laptop)

```
$ ls /sys/class/leds/dell\:\:kbd_backlight/
```

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## toralf

 *fedeliallalinea wrote:*   

> In /sys/class/leds/ you have some entry referencing on keyboard backlight?
> 
> In my system (laptop)
> 
> ```
> ...

 Weöll, I do have 

```
# pwd

/sys/class/leds/tpacpi::kbd_backlight

t44 tpacpi::kbd_backlight # ls -l

total 0

-rw-r--r-- 1 root root 4096 May  1 20:40 brightness

lrwxrwxrwx 1 root root    0 May  1 20:39 device -> ../../../thinkpad_acpi

-r--r--r-- 1 root root 4096 May  1 12:46 max_brightness

drwxr-xr-x 2 root root    0 May  1 20:39 power

lrwxrwxrwx 1 root root    0 May  1 12:46 subsystem -> ../../../../../class/leds

-rw-r--r-- 1 root root 4096 May  1 20:39 trigger

-rw-r--r-- 1 root root 4096 May  1 12:45 uevent

```

but that doesn't help, writing any value of 0, 1 or 2 to the file brightness doesn't show any effect.

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## R0b0t1

Hello,

It looks like it's using the Thinkpad driver - is that actually the right one? Do you know how the backlight is managed when used with Windows? Most non-laptop keyboards I have seen manage the brightness themselves with hotkey combinations that are not interpreted by the OS.

I just found this question - https://askubuntu.com/questions/13886/how-to-light-up-back-lit-keyboard - which was going to be my other guess for how the backlight is exposed. Apparently it might be another LED on your keyboard like the number, capitalization, or scroll locks, and could be exposed via the HID driver.

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## Roman_Gruber

 *Quote:*   

> VENDOM Illuminated Scissor Keyboard, black

 

most of the time, a hidden kernel module + setting

when there is a module for it, if not.

https://github.com/terrycain/razer-drivers/wiki/Reverse-Engineering-USB-Protocol

 *Quote:*   

> There are a few things you will need when reverse engineering the USB protocol device. Firstly you will need a device . You will also need an additional keyboard, Virtualbox, VirtuaBox Extensions Pack, a Windows VM (I normally use 7 for this, but this has been reported to work),  ...

 

 *Quote:*   

> 
> 
> It looks like it's using the Thinkpad driver - is that actually the right one? Do you know how the backlight is managed when used with Windows? Most non-laptop keyboards I have seen manage the brightness themselves with hotkey combinations that are not interpreted by the OS. 

 

Since uefi and a few years. every hid has its own firmware and its own written tools by the manufacturer how to set the magic bits. 

the link above gives a good insight for starters

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## toralf

 *R0b0t1 wrote:*   

> https://askubuntu.com/questions/13886/how-to-light-up-back-lit-keyboard

 Hhm, just FWIW, 

```
xset led 3
```

switches on the LED for caps lock.

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## R0b0t1

 *toralf wrote:*   

>  *R0b0t1 wrote:*   https://askubuntu.com/questions/13886/how-to-light-up-back-lit-keyboard Hhm, just FWIW, 
> 
> ```
> xset led 3
> ```
> ...

 

Have you tried every number?

The reason I don't think there is a custom driver is because unlike a laptop keyboard, which can put the LED controller on an internal I2C bus, the USB keyboard LEDs must be controlled via USB in some way. It is possible to create multiple USB endpoints but that should be something you would be able to detect.

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