Display brightness requires manual intervention

Looks more for me like a Bios or acpi-support issue but anyway please attach the file /var/log/Xorg.0.log.
If you want to be sure use the vesa driver and check if the brightness problem still appears. Add the line >>Driver "vesa"<< under the Device section in your /etc/X11/xorg.conf and then restart X.

Yes, you're right. I just booted up in recovery mode and around the time the screen dimmed, I saw something about acpi video fly up the screen. Where are these boot time messages logged?

After booting up, I have this:

joss@laptop:~$ cat /proc/acpi/video/GFX0/LCD/brightness
levels: 100 57 0 14 28 43 57 71 86 100
current: 0
joss@laptop:~$

If I use the Fn keys to increase the brightness to 100, I get this:

joss@laptop:~$ cat /proc/acpi/video/GFX0/LCD/brightness
levels: 100 57 0 14 28 43 57 71 86 100
current: 100
joss@laptop:~$

If I unplug the AC power, I get this:

joss@laptop:~$ cat /proc/acpi/video/GFX0/LCD/brightness
levels: 100 57 0 14 28 43 57 71 86 100
current: 43
joss@laptop:~$

When I plug AC power back in, I get this:

joss@laptop:~$ cat /proc/acpi/video/GFX0/LCD/brightness
levels: 100 57 0 14 28 43 57 71 86 100
current: 86
joss@laptop:~$

And when I unplug it again:

joss@laptop:~$ cat /proc/acpi/video/GFX0/LCD/brightness
levels: 100 57 0 14 28 43 57 71 86 100
current: 28
joss@laptop:~$

and plug it in:

joss@laptop:~$ cat /proc/acpi/video/GFX0/LCD/brightness
levels: 100 57 0 14 28 43 57 71 86 100
current: 71
joss@laptop:~$

So, you can see, it's incrementally decreasing every time I unplug AC.

So, for me, there's two problems:

1. On boot, brightness is dimmed to 0
2. Unplugging AC repeatedly, incrementally decreases the display brightness.

Each problem can be overcome by using the Fn keys after boot and plugging AC back in, but it's clearly not how it should work.

Thanks for any help with this. Please point me to logs or anything I can do help debug it further.

Joss

Ok, changing to acpi-support for now. I guess the output of dmesg and the file /var/log/syslog might give some useful information.
So the brightness changed in recovery mode without X in console? I would also check the Bios if there are some brightness settings and maybe check if you could change brightness in Bios with the keys. If it works there it should be independent from running Os.

Brightness control works before the OS is loaded. i.e. I can use the Fn keys to increase/decrease brightness at the bios screen before the OS loads. If I do increase it to 100%, the OS decreases the display brightness around the time the acpi video driver is loading. You're right, it's clearly unrelated and independent of X.

I don't have access to the laptop right now but I'm pretty sure there's no brightness settings in the bios. Will confirm and attach logs later.

Thanks

I have confirmed this behavior my Lenovo T42p and T61p.

Here are three log files. I've checked my bios, and there's no option to adjust the display.

Thanks for any help with this.

Maybe you can temporarily blacklist the acpi video module. It is called video according to http://www.thinkwiki.org/wiki/Problem_with_LCD_brightness_buttons#Workaround .

I've blacklisted the video module and the screen does not noticeably dim on boot. However, the Fn key controls no longer work and nor does display dimming on battery power. I get better functionality with the video module loaded, despite the reported problem above. The Thinkpad fixes don't work for my Lenovo 3000 N100.

I've attached the logs when the video module is blacklisted.