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wpovell

Member

Registered: 2017-10-18

Posts: 9

[SOLVED] Brightness on Thinkpad X1 Carbon 5th Gen

Version: 4.15.13-1-ARCH

I have a Thinkpad X1 Carbon 5th gen and have never been able to get the brightness to work on arch. I've looked at the wiki page for the laptop, which says that this used to be a problem but supposedly got fixed in 4.14 (however it still doesn't work for me). The old solution of adding acpi_brightness=vendor as a kernel param also doesn't cause any change for me.

In journalctl I have the following bit of logs that seems relevant (but I don't really understand):

Jan 03 17:14:04 lambda kernel: thinkpad_acpi: ThinkPad ACPI Extras v0.25
Jan 03 17:14:04 lambda kernel: thinkpad_acpi: http://ibm-acpi.sf.net/
Jan 03 17:14:04 lambda kernel: thinkpad_acpi: ThinkPad BIOS N1MET37W (1.22 ), EC unknown
Jan 03 17:14:04 lambda kernel: thinkpad_acpi: Lenovo ThinkPad X1 Carbon 5th, model 20HRS14W00
Jan 03 17:14:04 lambda kernel: thinkpad_acpi: radio switch found; radios are enabled
Jan 03 17:14:04 lambda kernel: thinkpad_acpi: This ThinkPad has standard ACPI backlight brightness control, supported by the ACPI video driver
Jan 03 17:14:04 lambda kernel: thinkpad_acpi: Disabling thinkpad-acpi brightness events by default...
Jan 03 17:14:04 lambda kernel: thinkpad_acpi: rfkill switch tpacpi_bluetooth_sw: radio is unblocked
Jan 03 17:14:04 lambda kernel: thinkpad_acpi: Standard ACPI backlight interface available, not loading native one

Last edited by wpovell (2018-04-01 19:02:50)

HalosGhost

Forum Fellow

From: Twin Cities, MN

Registered: 2012-06-22

Posts: 2,097

Website

Re: [SOLVED] Brightness on Thinkpad X1 Carbon 5th Gen

Okay,

Do you have any folders in /sys/class/backlight? If so, does one of those entries have a brightness file? If so, can you echo a number into it to change the brightness?

If the answer to all the above questions was “yes”, then there are several tools out there that can be used to manage your backlight brightness in a very simple way (full disclosure, this one is mine) which you could bind your keys to in your WM/DE.

If not, which step did things fall apart at?

All the best,

-HG

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wpovell

Member

Registered: 2017-10-18

Posts: 9

Re: [SOLVED] Brightness on Thinkpad X1 Carbon 5th Gen

I have two folders under /sys/class/backlight, thinkpad_screen and intel_brightness. Both have a brightness file, however I am unable to echo anything into either. For example,

echo 2 > /sys/class/backlight/thinkpad_screen/brightness
bash: /sys/class/backlight/thinkpad_screen/brightness: Permission denied

lo1

Member

Registered: 2017-09-25

Posts: 584

Re: [SOLVED] Brightness on Thinkpad X1 Carbon 5th Gen

echo 2 > /sys/class/backlight/thinkpad_screen/brightness
bash: /sys/class/backlight/thinkpad_screen/brightness: Permission denied

Just prepend sudo before the command. Nope, this won't work because the user shell will handle redirection over sudo. Actually, if intel_brightness works fine with the command above, you can remove the acpi_brightness=vendor kernel parameter.

EDIT: fixed my ignorance

Last edited by lo1 (2018-04-01 15:34:58)

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V1del

Forum Moderator

Registered: 2012-10-16

Posts: 25,435

Re: [SOLVED] Brightness on Thinkpad X1 Carbon 5th Gen

You can't sudo an echo redirect, either use a root shell or use some intermediate utility like tee

echo 2 | sudo tee /sys/class/backlight/thinkpad_screen/brightness

ewaller

Administrator

From: Pasadena, CA

Registered: 2009-07-13

Posts: 20,721

Re: [SOLVED] Brightness on Thinkpad X1 Carbon 5th Gen

You can't sudo an echo redirect, either use a root shell or use some intermediate utility like tee

echo 2 | sudo tee /sys/class/backlight/thinkpad_screen/brightness

Or, my preference sudo bash -c "echo 2 > /sys/class/backlight/thinkpad_screen/brightness"

After you figure out which one you want to use, you might disable the other with a command line directive.  For example, My command line:

ewaller@turing ~ 1005 %cat /proc/cmdline 
root=/dev/sda6 initrd=/intel-ucode.img initrd=/initramfs-linux.img acpi_backlight=native
ewaller@turing ~ 1006 %

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wpovell

Member

Registered: 2017-10-18

Posts: 9

Re: [SOLVED] Brightness on Thinkpad X1 Carbon 5th Gen

Thanks so much! Everything is working now. I didn't realize that redireting sudo didn't actually write as root, makes sense though!

HalosGhost

Forum Fellow

From: Twin Cities, MN

Registered: 2012-06-22

Posts: 2,097

Website

Re: [SOLVED] Brightness on Thinkpad X1 Carbon 5th Gen

Glad you got it figured out.

Now, go forth and pick the sysfs-based backlight manager of your choice.

All the best,

-HG

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jarlah

Member

Registered: 2018-06-27

Posts: 4

Re: [SOLVED] Brightness on Thinkpad X1 Carbon 5th Gen

using a x1 carbon 5th generation here on 4.17.2-1-ARCH. Brightness works flawlessly. But I have intel video and 1920x1080 screen. No nvidia+intel combo here. With intel only x1 carbon is rock solid on arch. The brightness buttons can however be a little bit tricky because of the Fn-Lock. If Fn-Lock is off you can just hit the buttons directly. But with Fn-Lock on you have to use Fn-[BrightnessKey]

Last edited by jarlah (2018-06-27 13:36:50)

HalosGhost

Forum Fellow

From: Twin Cities, MN

Registered: 2012-06-22

Posts: 2,097

Website

Re: [SOLVED] Brightness on Thinkpad X1 Carbon 5th Gen

Jarlah,

welcome to the BBS. This topic was already marked [SOLVED] several months ago, and it doesn't look like your post is proposing a new problem (just a tip).

Please avoid bumping already-solved threads. If you have a new problem (even if related), opening a new thread is appropriate.

Closing.

All the best,

-HG

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