lightwatch.pl is a long-running perl script which toggles the backlight when the xscreensaver activates. I configured my sessions to run it whenever I log in (Preferences->MorePreferences->Sessions). You need to make it suid root and install perl-suidperl. Bill "Vuud" Chmura created a second version which is aware of the AC power status.
When I start XFree86 4.2 it activates both my HD15 CRT output and the LCD. With this tool I can disable each of them. For reference my XF86Config-4 is available.
I have been unable to activate the TV out. It would be easier if I had the radeon documentation. Please feel free to send it to software (a) this hostname.
Thanks for patches from Deepak Chawla, Erno Kuusela, Rolf Offermanns, Soos Peter, and Matthew Strait (delayed blanking), Darin Nelson (radeon 9100 IGP) for radeontool patches.
Soos Peter wrote a very cool Linux kernel module radeonlcd which toggles the backlight when Linux blanks the framebuffer (i.e. console not XWindows).
Takanori Watanabe ported it to FreeBSD.
Apparently, the latest XFree86 in CVS (i.e. after 4.3.0) has a fix to control the backlight.
I learned that the backlight can be turned off on my Dell Inspiron C610 by Fn+D. It goes back on when I hit a key. Also Fn+Z fixes the fan and temperature sensor after software suspend! Why suspend doesn't do that automatically I will not understand.
I really like my Latitude C610 and its 1400x1050 screen, but please stop with the stupid screen resolution acronyms. Screens should be sold by megapixel just like cameras: 1.47 megapixel.
I have had troubles with it overheating. Apparently, the top PCMCIA slot is safer than the bottom one. It burned my Cisco WiFi card, and my Xircom Ethernet crashes the kernel when it gets too hot.
Once one of the screws fell out of the bottom. Dell sent free replacements, although it took us several tries to determine the right ones. Now, I tighten them every month and have had no more trouble.
I shall not buy another computer that pays the Microsoft tax, so this may be my last Dell laptop.
This tool is somewhat obsolete for controlling a VGA port, because xrandr can do it better. Run it without options to see the manageable outputs...
[fdd@jibsheet ~]$ xrandr Screen 0: minimum 320 x 200, current 1920 x 1200, maximum 1920 x 1920 VGA-0 connected (normal left inverted right x axis y axis) 800x600 60.3 640x480 59.9 DVI-0 disconnected (normal left inverted right x axis y axis) LVDS connected 1920x1200+0+0 (normal left inverted right x axis y axis) 331mm x 207mm 1920x1200 60.0*+ 1400x1050 60.0 1280x1024 60.0 1280x960 60.0 1024x768 60.0 800x600 60.3 640x480 59.9
Then turn them off (--off) or on (--auto).
[fdd@jibsheet ~]$ xrandr --output VGA-0 --off [fdd@jibsheet ~]$ xrandr --output VGA-0 --auto
Strangely, sometimes the backlight doesn't come back on immediately, so I have to change my resolution, or use Ctrl-Alt-number to switch consoles then come back.
[fdd@jibsheet ~]$ xrandr --output LVDS --mode 1400x1050 [fdd@jibsheet ~]$ xrandr --output LVDS --mode 1920x1200
Although xrandr --off is more than just controlling the backlight, as it could move your windows around and such, when the larger resolution becomes unavailable.
BTW, if you are like me and your VGA does not have many modes you can manually add them such as like this...
xrandr --newmode my_1280x1024 108.0 1280 1328 1440 1688 1024 1025 1028 1066 +hsync +vsync xrandr --addmode VGA-0 my_1280x1024 xrandr --newmode my_1680x1050 119.0 1680 1728 1760 1840 1050 1053 1059 1080 +hsync +vsync xrandr --addmode VGA-0 my_1680x1050 xrandr --output VGA-0 --mode my_1280x1024
Soon the kernel may be denying the trick radeontool uses to poke the video hardware from userspace behind the drivers back. See http://lwn.net/Articles/307993/ section "Exclusive I/O memory".