# How is monitor brightness controlled?



## Ievgen (May 8, 2012)

Hi,

I've recently installed FreeBSD 9.0 RELEASE with a new Xorg and KMS patch. I've never had any issues with controlling the monitor brightness on my other laptops but this time I've got this issue with my Optimus Dell Inspiron laptop.

Pressing the Fn + F4/F5 combinations doesn't have any effect in KDE4, and the worst is that I don't know where to start looking at, I don't know what thing is responsible for controlling the monitor brightness. 

Could you point me in the right direction so I could provide more explicit details about my configuration if anybody is willing to help me?

P.S. 
There is one interesting observation. By pressing Fn+F5 (brightness up) in open terminal produces an unlimited sequence of '.' characters which can be interrupted by pressing any key.

```
devel-pc# .......................................
```

Some system details:

```
FreeBSD devel-pc 9.0-RELEASE FreeBSD 9.0-RELEASE #0: Fri Apr 27 15:19:53 EEST 2012     
root@devel-pc:/usr/obj/usr/src/sys/GENERIC  amd64
Xorg: 7.5.2
kde4: 4.7.3
xf86-video-intel: 2.17.0  
devel-pc# kldstat
Id Refs Address            Size     Name
 1   54 0xffffffff80200000 11d2570  kernel
 2    1 0xffffffff81612000 1582     fdescfs.ko
 3    1 0xffffffff81614000 42a7     linprocfs.ko
 4    1 0xffffffff81619000 1e1cb    linux.ko
 5    1 0xffffffff81638000 328d     ng_ubt.ko
 6    1 0xffffffff8163c000 8b3d     ng_hci.ko
 7    3 0xffffffff81645000 a79      ng_bluetooth.ko
 8    5 0xffffffff81646000 8e12     netgraph.ko
 9    1 0xffffffff8164f000 b4a2     ng_l2cap.ko
10    1 0xffffffff8165b000 1695e    ng_btsocket.ko
11    1 0xffffffff81672000 1ba9     ng_socket.ko
12    1 0xffffffff81674000 a96b     fuse.ko
13    1 0xffffffff8167f000 5f29b    i915.ko
14    1 0xffffffff816df000 1241     iicbb.ko
15    4 0xffffffff816e1000 1307     iicbus.ko
16    1 0xffffffff816e3000 dc9      iic.ko
17    1 0xffffffff816e4000 2c4b2    drm.ko
18    1 0xffffffff81711000 248d     acpi_video.ko
```


----------



## ring_zero (May 17, 2012)

Try selecting a different keyboard model in Systemsettings -> Input Devices -> Keyboard.  I did not see your specific Dell listed, but I did see an option for a generic Dell layout.  You might have to play around with it.  I do not have a Dell so I can't say for sure, mine just worked when I loaded acpi_video. This is from the acpi_video(4) man page:
	
	



```
DESCRIPTION
     This driver uses the ACPI Video Extensions to control display switching
     and backlight brightness.  The availability of the sysctl(8) variables
     depends on the functions offered by the host's ACPI implementation.
```
  Hopefully this will provide a starting point for you.


----------



## Ievgen (May 18, 2012)

Thanks for reply, I've done what you had advised but it does not work. The problem is that there is no Dell specific ACPI module for FreeBSD. Loading acpi_video does not add any brigthness related system variables which I could alter via sysctl.

For example:

```
devel-pc# sysctl -a | grep lcd
devel-pc# sysctl -a | grep bright
```


----------



## dndlnx (May 18, 2012)

```
xbacklight -set number
```

Number is from 0 to 100, for brightness %.


----------



## Ievgen (May 18, 2012)

```
> sudo xbacklight -set 50
No outputs have backlight property
```


----------



## ring_zero (May 22, 2012)

Ievgen said:
			
		

> Thanks for reply, I've done what you had advised but it does not work. The problem is that there is no Dell specific ACPI module for FreeBSD. Loading acpi_video does not add any brigthness related system variables which I could alter via sysctl.
> 
> For example:
> 
> ...


 There is no Toshiba specific module for amd64 either,  I am aware of toshiba_acpi, but it does not work on amd64 for me.  The acpi_video module does work, and that is all I am using.  I do not have any of the other hotkeys, i.e volume.  I believe the problem is being caused by the Optimus technology.  NVIDIA does not support Optimus technology on any platform other than windows.  You could try disabling Optimus in the BIOS, and see if that helps, but unless I am mistaken (a very likely possibility), this will confine you to using the Intel adapter.  Unfortunately, the Intel 3000 chip is unsupported by FreeBSD at present, so you will have to use the VESA driver, which is very limited. You can also try the GEM/KMS patches, but they are incomplete. See the following threads: here,here, and here for more info.  No guarantees, but I bet this is significantly contributing to, if not causing your problem.


----------



## Ievgen (May 22, 2012)

I'm not making use of Nvidia, see the head message here. I've applied patches to make Intel chip work


----------



## ring_zero (May 22, 2012)

Yeah, I just noticed that.  It looks like acpi backlight controls are not available at the moment.  See here. The message mentions using dcdbas SMI interface.  I don't know how the author has gotten it to work, dcdbas is part of libsmbios which is part of a Dell kernel module for Linux.  I wish that I could have been a little more helpful to you, but I don't really use Dell.


----------

