Enable brightness scaling on different hardware models

[Nicolas Joyard]

Using Ubuntu 13.04, gnome-settings-daemon 3.6.4-0ubuntu8.

Different hardware have different brightness scales, for example :
- ranges are different ('max_brightness' value)
- some hardware turns backlight off when brightness is 0
- some hardware have a linear scale, some do not

For example, on an EeePC 1215N, the brightness ranges from 0 to 8 and changes are nearly linear (the increase between 0 and 1 seems similar to the increase between 7 and 8). On a Zenbook UX32VD, the brightness ranges from 0 to 100, with 0 turning the backlight completely off, and changes are a lot less linear (the increase between 1 and 2 seems similar to the increase between 90 and 100).

It would be nice to allow configuring a different scale on different hardware so that brightness changes seem more linear.

[Sebastien Bacher (seb128)]

Thank you for taking the time to report this bug and helping to make Ubuntu better. The issue you are reporting is an upstream one and it would be nice if somebody having it could send the bug to the developers of the software by following the instructions at https://wiki.ubuntu.com/Bugs/Upstream/GNOME. If you have done so, please tell us the number of the upstream bug (or the link), so we can add a bugwatch that will inform us about its status. Thanks in advance.