Ubuntu
linux package

  1. Bug #868208
  2. Comment #2

Comment 2 for bug 868208

Revision history for this message
Rainer (rainerf) wrote :

Disabling VT-d fixed the freezes for my T420s (with NVS 4200M set to discrete graphics), and with Option "RegistryDwords" "EnableBrightnessControl=1" as described in bug 776999 changing the brightness even works again.

I also get
[ 4.682864] thinkpad_acpi: detected a 8-level brightness capable ThinkPad
during bootup. Interestingly, this seems correct for increasing the brightness: there seem to be 8 levels. Decreasing, however, seems to be more fine-grained since there are 16 levels before nothing changes anymore. Don't know if this is important somehow, however ;).

BTW: For Kubuntu, the system hanging on changing the brightness means that it is completely unusable since KDE seems to try to lower the brightness right during the startup.