luxd always sets the screen to minimum brightness

[Stuart Pook]

I have a Google (Asus) Nexus 7. If I use "System Settings...." -> "Brightness & Lock" to change the screen brightness the brightness changes as I move the cursor but goes back to minimum brightness as soon as I stop moving the cursor.

If I try to set the brightness by hand I see the same thing.

stuart@stuart-nexus7:~$ cat /sys/class/backlight/*/brightness
0
stuart@stuart-nexus7:~$ echo 128 | sudo tee /sys/class/backlight/*/brightness
128
stuart@stuart-nexus7:~$ cat /sys/class/backlight/*/brightness
0

It is /usr/bin/luxd that is broken. It reads /sys/bus/i2c/drivers/al3010/2-001c/show_lux, divides the result by 100 and sets /sys/class/backlight/pwm-backlight/brightness to the resulting value. Under normal office lighting:

stuart@stuart-nexus7:/etc$ cat /sys/bus/i2c/drivers/al3010/2-001c/show_lux
38

Under a bright lamp:

stuart@stuart-nexus7:/etc$ cat /sys/bus/i2c/drivers/al3010/2-001c/show_lux
127
stuart@stuart-nexus7:/etc$ echo $(($(cat /sys/bus/i2c/drivers/al3010/2-001c/show_lux) / 100))
1

Dividing show_lux by 100 to get brightness seems incorrect as show_lux seems to go up to about 127 and brightness goes from 0 to 255.

I fixed the problem by killing luxd. In any case I don't a need a shell script looping once a second as my Nexux 7 is already too slow.

ProblemType: Bug
DistroRelease: Ubuntu 13.04
Package: ubuntu-defaults-nexus7 0.52
Uname: Linux 3.1.10-9-nexus7 armv7l
ApportVersion: 2.8-0ubuntu4
Architecture: armhf
Date: Tue Feb 5 14:38:45 2013
MarkForUpload: True
PackageArchitecture: all
SourcePackage: ubuntu-defaults-nexus7
UpgradeStatus: No upgrade log present (probably fresh install)
mtime.conffile..etc.init.luxd.conf: 2013-02-05T14:26:59.308357
upstart.alsa-restore.override: manual
upstart.alsa-store.override: manual

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.