Comment # 12 on bug 967490 from Oliver Neukum

(In reply to Thomas Mitterfellner from comment #9)

> root@linux:~> for i in /sys/bus/usb/devices/1-6:1.0/power/* ; do echo -n
> "$i: " ; cat $i ; done
> /sys/bus/usb/devices/1-6:1.0/power/async: enabled
> /sys/bus/usb/devices/1-6:1.0/power/runtime_active_kids: 0
> /sys/bus/usb/devices/1-6:1.0/power/runtime_enabled: enabled
> /sys/bus/usb/devices/1-6:1.0/power/runtime_status: suspended
> /sys/bus/usb/devices/1-6:1.0/power/runtime_usage: 0
> 
> Interesting thing is: when I do lsusb -v, the light goes out!

When you do lsusb as root, the device usage count is upped to allow retrival of
the descriptors and lowered again. If you land at zero, a runtime suspension
is triggered on video devices.
Unfortunately there are at least two obvious potential causes

1) a fatal error returned from suspend()
2) the wrong kind of primitive is used in the uvc driver

First we need to confirm this theory. Could you do

cat /sys/bus/usb/devices/$DEVICE/power/level
echo on > /sys/bus/usb/devices/$DEVICE/power/level
echo auto > /sys/bus/usb/devices/$DEVICE/power/level

Your light should go out after 2 seconds. What is the result of the cat?