Brightness only moves between 100% and 0% on Lenovo SL510

[pythonscript]

I have a Lenovo SL510 laptop, and the brightness appears to only have two settings: 100% and 0%. If I use the brightness keys on the laptop and decrease the brightness, it immediately drops to 0%. The same thing happens if I increase the brightness; it automatically jumps to 100%.

From lsmod, these are the acpi kernel modules I have installed:

Code: Select all

Module                  Size  Used by

thinkpad_acpi          61270  0 
nvram                  13049  1 thinkpad_acpi
acpi_cpufreq           12935  1 
snd                    52850  17 snd_timer,snd_seq_device,snd_seq,snd_rawmidi,thinkpad_acpi,snd_pcm,snd_mixer_oss,snd_pcm_oss,snd_hwdep,snd_hda_codec,snd_hda_intel,snd_hda_codec_realtek,snd_hda_codec_hdmi
rfkill                 19012  6 cfg80211,thinkpad_acpi,bluetooth
mperf                  12453  1 acpi_cpufreq
processor              28157  3 acpi_cpufreq

From uname -r, my kernel version is 3.2.0-4-amd64.

Is there any other information I need to provide to troubleshoot this?

[pythonscript]

Does anyone have any ideas? I have several directories in /sys/class/backlight, specifically:

Code: Select all

acpi_video0  intel_backlight

In both folders, I have a file named brightness. In brightness the file contains the number 15, but if I try:

Code: Select all

echo 14 > brightness

the screen immediately goes black just like when I use the buttons. Although the brightness in intel_backlight contains the value 4422465 initially (obviously much larger than 15), writing a different value to it has the same result.

Also, I installed the xbacklight package and tried advice I found through google:

Code: Select all

xbacklight -set 13

but once again, this immediately darkens the screen. No matter what value I try for this (I tried 0 to 1 million in a bash script) the screen immediately goes dark.

Are there any other resources I can consult (I've tried google numerous times, but there could be something I'm missing), other forums, mailing lists, etc.? My laptop isn't usable as a laptop because this is absolute death for battery life. Everything I can find says brightness is fully supported on the SL510, so I really need help figuring out what the problem is.

[infinity9]

Have you tried "acpi_backlight=vendor" in the boot parameters? it worked for me in Lenovo G580.