2013/5/20 Daniel Vetter daniel@ffwll.ch
On Sat, May 18, 2013 at 12:39:14AM +0200, Jan Hinnerk Stosch wrote:
Hallo,
I hope this is the right place to ask, because I actually don't know whether it is a bug or a feature that I'm experiencing since linux 3.9: When I boot my system the backlight gets extremely bright compared to
older
kernel versions. It is most obvious when I leave X (more a yellow than a black background), but I have the impression, that the colors in X are brighter than usual, too. I used my spare time this afternoon to do a kernel bisect and learned
that
the first "bad" commit is 55bc60db5988c8366751d3d04dd690698a53412c. As I don't have insight or understanding of the code: Is this behaviour
intended
and how could I change it to the old state or is it a bug and should I report it somewhere? My system is as follows: Intel i5-3570k with Intel HD 4000 my monitor is connected via HDMI. If you need any more information just tell me.
Yeah, this is a feature. HDMI has (for oddball backwards compat with analog TV signals) a special mode which reduces the useable RGB value range by chopping off about 10% at the bottom and top end. This results in light colors getting brighter and dark colors getting darker.
The above mentioned commit tries (to the best of our knowledge) to auto-set the option which most likely fits what the hdmi sink will do with the color data. You can either fix this up in the hdmi sink with the on-screen menu or by manually setting the "RBG Broadcast" property for the relevant hdmi connector to the setting you want.
Cheers, Daniel
Daniel Vetter Software Engineer, Intel Corporation +41 (0) 79 365 57 48 - http://blog.ffwll.ch
Ok, thank you for your detailed explanation.
Regards, jhs