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defer-
Tux's lil' helper
Joined: 11 Jun 2007
Posts: 140
Location: Finland
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 Posted: Sun Apr 13, 2014 6:46 pm Post subject: [solved] thinkpad E531 screen brightness |
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I havent managed to get screen brightness to work on thinkpad E531. I tried ubuntu livecd and screen brightness controls work in it. I have built all the modules that was loaded on ubuntu livecd but brightness still doesnt work.
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Last edited by defer- on Tue Apr 15, 2014 11:02 am; edited 2 times in total |
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chithanh
Developer
Joined: 05 Aug 2006
Posts: 2158
Location: Berlin, Germany
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| Posted: Sun Apr 13, 2014 7:08 pm Post subject: |
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Check if you have brightness controls in a subdirectory /sys/class/backlight/ and are using the thinkpad_acpi driver for the hotkeys.
Sometimes, acpi_backlight=vendor kernel parameter is necessary for backlight control to work. |
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defer-
Tux's lil' helper
Joined: 11 Jun 2007
Posts: 140
Location: Finland
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| Posted: Sun Apr 13, 2014 10:03 pm Post subject: |
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I tried acpi_backlight=vendor but its still not working.
| Code: |
defer ~ $ ls /sys/class/backlight/intel_backlight/
actual_brightness bl_power brightness device max_brightness power subsystem type uevent
defer ~ $ dmesg | grep thinkpad
[ 1.882819] Failed to find thinkpad-acpi symbol tpacpi_led_set
[ 12.337470] thinkpad_acpi: ThinkPad ACPI Extras v0.25
[ 12.337472] thinkpad_acpi: http://ibm-acpi.sf.net/
[ 12.337473] thinkpad_acpi: ThinkPad BIOS HEET41WW (1.22 ), EC unknown
[ 12.337474] thinkpad_acpi: Lenovo ThinkPad Edge E531, model 6885BPG
[ 12.337846] thinkpad_acpi: Unsupported brightness interface, please contact ibm-acpi-devel@lists.sourceforge.net
[ 12.339238] thinkpad_acpi: rfkill switch tpacpi_bluetooth_sw: radio is unblocked
[ 12.339760] thinkpad_acpi: Console audio control enabled, mode: monitor (read only)
[ 12.340826] input: ThinkPad Extra Buttons as /devices/platform/thinkpad_acpi/input/input9
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chithanh
Developer
Joined: 05 Aug 2006
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Location: Berlin, Germany
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| Posted: Sun Apr 13, 2014 10:33 pm Post subject: |
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| Code: | | /sys/class/backlight/intel_backlight/ |
That intel_backlight control is usually a dummy which doesn't work. A working backlight control is provided by ACPI_VIDEO in most cases. |
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defer-
Tux's lil' helper
Joined: 11 Jun 2007
Posts: 140
Location: Finland
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| Posted: Mon Apr 14, 2014 3:32 pm Post subject: |
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I can change brightness like this:
| Code: | | echo 2000 > /sys/class/backlight/intel_backlight/brightness |
But brightness keys doesnt work?
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sk8harddiefast
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Joined: 15 Feb 2009
Posts: 335
Location: athens
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| Posted: Tue Apr 15, 2014 4:02 am Post subject: |
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Did you check all the thinkpad options into kernel? Especially those for brightness, back light, FN keys etc. For ideapad laptops, they exist. Maybe for thinkpad too. Maybe they work the ideapad options on thinkpad too because both of them are lenovo.
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defer-
Tux's lil' helper
Joined: 11 Jun 2007
Posts: 140
Location: Finland
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| Posted: Tue Apr 15, 2014 9:34 am Post subject: |
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| Code: | <M> Lenovo IdeaPad Laptop Extras
<M> ThinkPad ACPI Laptop Extras
[*] Console audio control ALSA interface
[ ] Maintainer debug facilities
[ ] Verbose debug mode
[ ] Allow control of important LEDs (unsafe)
[*] Video output control support
[*] Support NVRAM polling for hot keys |
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chithanh
Developer
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| Posted: Tue Apr 15, 2014 10:17 am Post subject: |
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Can you check whether using the backlight keys actually changes the value of /sys/class/backlight/intel_backlight/brightness ?
The important option for backlight control is usually CONFIG_ACPI_VIDEO. |
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defer-
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Joined: 11 Jun 2007
Posts: 140
Location: Finland
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| Posted: Tue Apr 15, 2014 10:49 am Post subject: |
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Backlight controls doesnt change /sys/class/backlight/intel_backlight/brightness.
I have CONFIG_ACPI_VIDEO=y.
I get this error to dmesg when pressing backlight controls:
[48742.386351] ACPI: Failed to switch the brightness
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defer-
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Posts: 140
Location: Finland
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| Posted: Tue Apr 15, 2014 11:01 am Post subject: |
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Putting | Code: | | acpi_osi='!Windows 2012' |
to kernel cmdline fixed the issue. 
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