Ubuntu – LCD backlight keys on Fujitsu Siemens Amilo Pro

backlight

I have a FS Amilo Pro V3505, which runs 12.04 fine, apart from an anomoly with the brightness.

The function keys (Fn-F8 & Fn-F9) both control the LCD brightness as you would expect. However only the first key seems to register with the Notifications.
Running xev gives me the following for the brightness-down

FocusOut event, serial 33, synthetic NO, window 0x3800001,
    mode NotifyGrab, detail NotifyAncestor

FocusIn event, serial 33, synthetic NO, window 0x3800001,
    mode NotifyUngrab, detail NotifyAncestor

KeymapNotify event, serial 33, synthetic NO, window 0x0,
    keys:  2   0   0   0   0   0   0   0   0   0   0   0   0   0   0   0   
           0   0   0   0   0   0   0   0   0   0   0   0   0   0   0   0

but for the brightness up, I get:

KeyPress event, serial 33, synthetic NO, window 0x3800001,
    root 0xac, subw 0x0, time 7324412, (783,376), root:(785,466),
    state 0x0, keycode 120 (keysym 0x0, NoSymbol), same_screen YES,
    XLookupString gives 0 bytes: 
    XmbLookupString gives 0 bytes: 
    XFilterEvent returns: False

KeyRelease event, serial 33, synthetic NO, window 0x3800001,
    root 0xac, subw 0x0, time 7324564, (783,376), root:(785,466),
    state 0x0, keycode 120 (keysym 0x0, NoSymbol), same_screen YES,
    XLookupString gives 0 bytes: 
    XFilterEvent returns: False

cat /sys/class/backlight/intel_backlight/brightness returns 15625, and goes down to 0 when I turn down the brightness, but doesn't increase as the brightness goes up, despite the actual backlight increasing as expected. Writing anything to /sys/class/backlight/intel_backlight/brightness doesn't change either its value or the lcd brightness and there are no other entries in /sys/class/backlight.

I am running kernel 3.2.0-49, with an Intel 945GM chipset.

So, to summarise:

The function keys work as expected
The intel drivers expose the intel_brightness interface
The brightness interface and notifications work as expected when the brightness is decreasing but not when it is increasing
The intel_brightness interface cannot be used to change the brightness
There is no other software brightness control, e.g. No acpi interface.

Best Answer

Don't know if this answers are sufficient - here are links :

A workaround in arch Linux - but backlight is here only explained at edge.

https://wiki.archlinux.org/index.php/Intel_Graphics

And here is more detailed explanation concerning intel 945GM :

http://linux.die.net/man/4/intel

There beyond "Output Configuration" are the options of backlight.

As you can read there - brightness and backlight are two different things which can be adjusted.

xrandr --prop

delivers the current set datas.

Perhaps it is of matter if you install saucy-kernel 3.10 ( download it at ubuntu ) - only in case if you still use kernel 3.2.0-49 ? ( if this does not work, then you still have kernel 3.2.0-49 in your system to go back there ) :

http://kernel.ubuntu.com/~kernel-ppa/mainline/v3.10-saucy

So - don't know if Kernel 3.10 is necessary for below additions - you can test without danger after downloaded 3.10 suiting to your 64 or 32 processor :

sudo dpkg -i linux-*.deb

Sorry - now have seen that there is an extra package besides xrandr - it is called xbacklight

It is not installed by default:

sudo apt-get install xbacklight

xbacklight -get

delivers the current set value.

According to man xbacklight you can set it with:

xbacklight -set (here decimal value in percent !)

There is a special brightness for xbacklight to be set with:

xbacklight -inc (here decimal value increases in percent !)

and

xbacklight -dec (here decimal value decreases in persent !)

lowers the value down again - in case value was set too high.

Is your question answered ? - Let me know !

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