Unable to adjust brightness on laptop

paxolin · 04-18-2017, 09:43 AM

Quote:

Originally Posted by hydrurga

Ok, first run apt install xbacklight.

Then run xbacklight from the command line (e.g. xbacklight -set 50 and xbacklight -set 80) to see if it works.

Ah, does this mean I can't use the function keys to adjust the brightness any more?

hydrurga · 04-18-2017, 01:01 PM

Quote:

Originally Posted by paxolin

Ah, does this mean I can't use the function keys to adjust the brightness any more?

I don't think it means that, no. You're just going to eventually use that command to set the initial brightness of the screen on startup.

You can test the function keys once you've installed xbacklight.

paxolin · 04-20-2017, 04:47 AM

Hydrurga,

Sorry for the slow reply, been a little busy.

I was going to have a go at your suggestion, then I wondered if I need to do anything about the backlight control I've already installed?
Do I need to remove it first, to avoid any possible conflict with two lots of code doing the same thing?
If I do need to remove it, how do I go about that?

hydrurga · 04-20-2017, 05:03 AM

Quote:

Originally Posted by paxolin

Hydrurga,

Sorry for the slow reply, been a little busy.

I was going to have a go at your suggestion, then I wondered if I need to do anything about the backlight control I've already installed?
Do I need to remove it first, to avoid any possible conflict with two lots of code doing the same thing?
If I do need to remove it, how do I go about that?

No, the two in theory should work together. They both get at the same eventual settings. It's just that one links the function keys to the settings, the other provides a handy command-line interface.

business_kid · 04-21-2017, 02:58 AM

Sorry for long delay. Dunno about the packages you're being told to install. Try something like this to read the brightness

Code:

sudo cat /system/devices/. . . . /acpi/video0/actual_brightness

Use the full directory name, not like I did. That command line should return a number representing the current brightness. The max_brightness should give the max setting. You can then set it with a command like

Code:

echo 100 > /sys/blah. . ./acpi/video0/actual_brightness

Don't go above the max_brightness.

EDIT:You need to be root or use sudo to write the value