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#1 2012-10-06 08:08:58

kenwong
#! CrunchBanger
From: Hong Kong
Registered: 2009-07-26
Posts: 158

Display brightness levels (on Thinkpad T60)

On this machine, I can adjust the brightness of the display by pressing the Fn and Home/End buttons on the keyboard.  After booting into Waldorf, only 3 levels of brightness are available.  However, before booting into the desktop, there are at least 5 levels.  There are even 7 levels in Windows XP (dual boot alongside #!).

Any idea to make finer adjustments possible?  Thanks in advance.

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#2 2012-10-06 13:17:09

Neil
#! CrunchBanger
From: Paragould AR USA
Registered: 2010-05-01
Posts: 207

Re: Display brightness levels (on Thinkpad T60)

Try adding the kernel parameter in your grub boot line: acpi_backlight=vendor
and reboot.

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#3 2012-10-06 15:29:46

kenwong
#! CrunchBanger
From: Hong Kong
Registered: 2009-07-26
Posts: 158

Re: Display brightness levels (on Thinkpad T60)

^ Thanks Neil.  Unfortunately it doesn't make any changes.

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#4 2012-10-06 15:39:58

tao te
Member
From: Berlin
Registered: 2012-07-30
Posts: 43

Re: Display brightness levels (on Thinkpad T60)

Try:

echo "N" | sudo tee /sys/module/video/parameters/brightness_switch_enabled

... or:

echo "Y" | sudo tee /sys/module/video/parameters/brightness_switch_enabled

Then add the following to your autostart, with "N" or "Y", depending which enables the more levels.

echo "N" > /sys/module/video/parameters/brightness_switch_enabled

Last edited by tao te (2012-10-06 15:40:45)


T420s - i5-2520M, 4+4 GB Ram, 64 GB mSATA SSD, #! Linux

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#5 2012-10-07 13:42:44

kenwong
#! CrunchBanger
From: Hong Kong
Registered: 2009-07-26
Posts: 158

Re: Display brightness levels (on Thinkpad T60)

^ thanks tao te.

echo "Y" | sudo tee /sys/module/video/parameters/brightness_switch_enabled

gave me 4 levels, occasionally.  It behaves inconsistently.  In /sys/class/backlight/acpi_video0/max_brightness, the value is 7, which is the same as the brightness levels I have in Windows XP.

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#6 2012-10-07 18:10:02

Neil
#! CrunchBanger
From: Paragould AR USA
Registered: 2010-05-01
Posts: 207

Re: Display brightness levels (on Thinkpad T60)

Sorry...but about the best I can do is guess, as I have Xubuntu installed on my Thinkpad, and I have seven steps of brightness adjustment.  Don't know just what the dif would be.

Maybe try Tpb, and see if that offers any solution: http://www.thinkwiki.org/wiki/Tpb

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#7 2012-10-08 16:27:48

kenwong
#! CrunchBanger
From: Hong Kong
Registered: 2009-07-26
Posts: 158

Re: Display brightness levels (on Thinkpad T60)

I just tried Neil's suggestion again.

Neil wrote:

Try adding the kernel parameter in your grub boot line: acpi_backlight=vendor
and reboot.

It works now! Perhaps, I forgot to execute "sudo update-grub" before reboot last time.

It is still not very ideal.  I have only 5 levels (vs 7 levels in Win XP).  And the max brightness value is 7, as indicated in /sys/class/backlight/thinkpad_screen/max_brightness.

Also, the differences between these 5 levels are not equal.

Googling obtains some discussions about the strange behaviour of two steps instead of one made by each hit of the Fn+Home/End keys.  This is one of those reports:

http://askubuntu.com/questions/3834/len … one-lookin

Probably, these 5 brightness levels expressed in percentage term are:
0% --> 28.6% --> 57.2% --> 85.8 --> 100% [as 100/7 = 14.3]

Anyway, thanks Neil for your help.

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#8 2012-10-08 16:42:02

el_koraco
#!/loony/bun
From: inside Ed
Registered: 2011-07-25
Posts: 4,749

Re: Display brightness levels (on Thinkpad T60)

You can install xbacklight and map that to your hotkeys to increase by five percent or so. I can't guide you through it, read the xbacklight man page, look for the wiki article on xev to find the keycodes and look for rc.xml tweaks on how to do it.

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#9 2012-10-09 14:02:05

kenwong
#! CrunchBanger
From: Hong Kong
Registered: 2009-07-26
Posts: 158

Re: Display brightness levels (on Thinkpad T60)

Thanks el_koraco.  Will take a look at it.

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#10 2012-10-09 14:36:11

kenwong
#! CrunchBanger
From: Hong Kong
Registered: 2009-07-26
Posts: 158

Re: Display brightness levels (on Thinkpad T60)

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#11 2012-10-10 06:37:04

shem
#! Member
From: Universe 6.62606957(29)×10−34
Registered: 2012-05-16
Posts: 78

Re: Display brightness levels (on Thinkpad T60)

On my laptop Asus K93S, I get the 10 levels of brightness back (instead of 5) by using the temporary solution in comment 13 on the xfce bugzilla:

xfconf-query -c xfce4-power-manager -n -t bool -p /xfce4-power-manager/change-brightness-on-key-events -s false

(Edit: Added link + corrected)

Last edited by shem (2012-10-10 06:38:48)

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#12 2012-10-10 10:16:15

tao te
Member
From: Berlin
Registered: 2012-07-30
Posts: 43

Re: Display brightness levels (on Thinkpad T60)

Great! Thanks shem.

To disable the buggy brightness OSD, use:

xfconf-query -c xfce4-power-manager -n -t bool -p /xfce4-power-manager/show-brightness-popup -s false

T420s - i5-2520M, 4+4 GB Ram, 64 GB mSATA SSD, #! Linux

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#13 2012-10-28 16:16:41

kenwong
#! CrunchBanger
From: Hong Kong
Registered: 2009-07-26
Posts: 158

Re: Display brightness levels (on Thinkpad T60)

Alternatively, install the package xfce4-settings and use the command xfce4-settings-editor.

After adding the change-brightness-on-key-events key and setting the value to false, I now have 7 steps.  However, the bar in the brightness on screen level pop-up is now blank always (i.e., indicates zero whatever the actual brightness level is).  I therefore disabled it.

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