Insomniac screen can't dpms suspend/standby/off - wakes instantly

[Zorael]

Hello,


I have an MSI Wind U100 netbook clone, which exhibited the brightness
bug that recently urged Felix Geyer (debfx)'s powerdevil patch into
kdebase-workspace (https://bugs.launchpad.net/bugs/415023). The screen
of the same machine never sleeps, and it's been doing this for a good
while now, possibly throughout Karmic but worked in Jaunty.

Whenever it tries to dpms suspend/standby/off, the screen properly
goes dark, and then wakes instantly. When it does this, the brightness
OSD shows. Running dbus-monitor --system at the time, it reveals that
three brightness key events are apparently firing; down,down,down if
at 0% brightness, down,down,up otherwise.

debfx postulates (at the bug report linked above) that "[the] MSI Wind
seems to send brightness up/down key events on every brightness
change", and from what I gather, that the kernel seems to simulate a
keypress at the same time. This caused it to zoom up to 100%
brightness and then down to 0% whenever you tried to change brightness
(with keys or via the applet), or to oscillate between brightness
settings - all the while swamping the system with dbus messages with
soaring cpu usage.

Could this be an extension of the same issue? Could the hardware (or
kernel) also be sending/simulating keypresses when the screen turns
off, immediately causing it to wake again? Could powerdevil be told to
ignore brightness key events when listening for activity to break
dpms, perhaps across the board or at least if
laptop_panel.brightness_in_hardware is set to true? I was informed
that wouldn't be easy, so perhaps it's the wrong approach.

[18:21] <debfx> there is nothing powerdevil can do to prevent key events
[18:23] <debfx> hmm well yeah it could probably ignore them
[18:23] <debfx> i'll have a look at the code
[18:38] <debfx> doesn't seem that easy, by default powerdevil uses the
xsync extension to get notified on user activity

Thankfully it's a netbook so I can close the lid, otherwise the screen
will just unsuccessfully try to doze off every n minutes (as per
powerdevil settings) in perpetuity. The machine model/series itself is
plagued by various issues in Karmic, notably uvcvideo causing USB to
stop working (https://bugs.launchpad.net/bugs/435352), and no USB is
sort of a showstopper for a netbook. Both that bug and the brightness
bug have been listed as "also affects ubuntu-release-notes" in LP, so
hopefully it'll show up in Known Issues at release.


Thanks in advance,
JR