Detecting if display is powered on or not
pasik at iki.fi
Sun Oct 17 06:07:50 PDT 2010
While I was discussing the laptop lid/dock issues with Fedora
people this issue was brought up.
How do you determine if a display is actually powered on or not?
- Laptop in a docking station, lid open, so internal LVDS enabled.
- External DVI display connected, but powered off.
So in this case the external display shouldn't be used, since it's off.
What happens is this:
# cat /sys/class/drm/card0-DVI-D-1/status
# cat /sys/class/drm/card0-DVI-D-1/enabled
# cat /sys/class/drm/card0-DVI-D-1/modes
So it *looks* like it's enabled and active, but actually it's powered off.
Is there a method to determine the actual state?
That is pretty important information for the daemon/tool/script implementing
the "policy" of which outputs to enable/disable..
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