I believe the external monitor is actually not able to be dimmed or brightened from the system itself. I may be totally wrong here, but I think you actually have to use the brightness settings on your monitor.
As far as the low brightness, you may have to be using the other brightness file in /sys/class/backlight. There are typically two directories there and both control some separate element of brightness. For instance, I have acpi_video0 which goes from 1 to 15 and I have intel_backlight which was set at 4880 when I just checked. I don't know how high or now the intel_backlight goes and it is typically different from machine to machine.
Strangely, when I changed /sys/class/backlight/intel_backlight/backlight from 4880 to 3000 it got brighter... when I set it to around 1000 it is now similar to what it was before. I am now even more unsure as to how these two things relate. I just know that when I use my backlight keys (which worked out of the box) it adjusts the acpi_video0 directory, so that is what I use.
nardev, I think what you should do is learn how to actually write udev rules, as I have a sneaking suspicion that you simply copy and pasted what I exemplified above on a different machine and expected it to work.
I mostly agree.
1. For external monitor, i don't mind using brightness control on monitor. Actually i didn't even intend to change that brightness. My problem was monitor on laptop.
2. Concerning udev rules. Thing is that so many things changed. It's quite new concept for me. I read few Debian articles about that and i get an idea about it. Concerning copy/paste, well i don't see what else but the driver should i change there?
]]>As far as the low brightness, you may have to be using the other brightness file in /sys/class/backlight. There are typically two directories there and both control some separate element of brightness. For instance, I have acpi_video0 which goes from 1 to 15 and I have intel_backlight which was set at 4880 when I just checked. I don't know how high or now the intel_backlight goes and it is typically different from machine to machine.
Strangely, when I changed /sys/class/backlight/intel_backlight/backlight from 4880 to 3000 it got brighter... when I set it to around 1000 it is now similar to what it was before. I am now even more unsure as to how these two things relate. I just know that when I use my backlight keys (which worked out of the box) it adjusts the acpi_video0 directory, so that is what I use.
nardev, I think what you should do is learn how to actually write udev rules, as I have a sneaking suspicion that you simply copy and pasted what I exemplified above on a different machine and expected it to work.
]]>You know, I don't think this is the "right" way to do it, but I had trouble with a tmpfile not consistently setting the brightness on boot. So I tried a udev rule and it works consistently.
So your machine might be slightly different, but I think you can get the idea. This is what my rule contains:
# cat /etc/udev/rules.d/45-backlight.rules ACTION=="add", KERNEL=="acpi_video0", SUBSYSTEM=="backlight", SUBSYSTEMS=="pci", DRIVERS=="i915", ATTR{brightness}="2"
Of course you have to adjust for the brightness level. My machine (Thinkpad Edge E430) goes from 1 to 15 in acpi_video0, and as indicated by my "DRIVERS==", I use integrated Intel graphics.
I can't remember why I chose 45 for the filename, but I remember there was a reason. You may want to change that aspect.
Only result i get from this is that computer boots up with very low brightness.
What ever value (1 to 15) i try to write in /sys/class/backlight/acpi_video0/brightness nothing changes.
And, external monitor doesn't change at all. It's constantly very bright.
Any idea how to fix this?
It's T430 thinkpad with nvidia driver.
]]>But if it works, then thats great! Just know that the naming has significance if you ever start making rules for other things.
]]>So your machine might be slightly different, but I think you can get the idea. This is what my rule contains:
# cat /etc/udev/rules.d/45-backlight.rules
ACTION=="add", KERNEL=="acpi_video0", SUBSYSTEM=="backlight", SUBSYSTEMS=="pci", DRIVERS=="i915", ATTR{brightness}="2"
Of course you have to adjust for the brightness level. My machine (Thinkpad Edge E430) goes from 1 to 15 in acpi_video0, and as indicated by my "DRIVERS==", I use integrated Intel graphics.
I can't remember why I chose 45 for the filename, but I remember there was a reason. You may want to change that aspect.
]]>w /sys/class/backlight/acpi_video0/brightness 644 root root - 6
or
w /sys/class/backlight/acpi_video0/brightness 644 root root - '6'
(difference is the 6 is in quotes in the second one)
]]>-rw-r--r-- 1 root root 56 Jan 7 20:35 screen_brightness.conf
with the following content:
w /sys/class/backlight/acpi_video0/brightness - - - - 6
Unfortunatley it does not seem to work.
echo 6 > /sys/class/backlight/acpi_video0/brightness
works perfectly if executed as root.
What am I doing worng?
]]>echo 12 > /sys/class/backlight/acpi_video0/brightness
as root should do the trick. If you have more than one screen you can use
for i in /sys/class/backlight/acpi_video*/brightness; do echo 0 > $i; done
Add that somewhere where it will be executed at boot or login, and you should be good to go.
]]>I use TLP for the power management and that does not have a screen brightness default setting in /etc/defaults/tlp.
Where can I set this?
]]>