[Lcms-user] ddc/ci and color management

[Sanford R. <roc...@mi...>]

I apologize in advance for posting a question about DDC/CI to this list, 
as it's not quite on topic.  People here have been very helpful and I'd 
certainly appreciate suggestions as to a more appropriate place to post.

When I perform a calibration, it's specific to the current settings of 
the monitor: color temperature, RGB channel settings, brightness, etc. 
Yet handling these settings is an out of band process.  It's the user's 
responsibility to manually adjust the monitor settings and record the 
values before calibration, and restore them manually if necessary.  At 
the very least, it would be desirable to record those settings in the 
profile, or even just have a utility that allowed me to record the 
settings and possibly restore them.

All this should be possible with DDC/CI, but DDC/CI doesn't seem to be 
supported on Linux.   There's ddccontrol, but it doesn't appear to have 
been updated in years.   When I try to run it, it doesn't recognize my 
monitors or complains that the data returned is invalid.   I've tried 
using i2cdump.  I can read the EDID data at address 0x50.  My 
understanding is that the DDC data is at address 0x30, but when I read 
from that address I get nothing.  xcmddc can identify the i2c buses for 
monitors, but that's about it.  The comments in XcmDDC suggest that much 
greater capabilities were intended.

Googling, I find a bunch of posts from Kae-Uwe Berman, Graeme Gill, 
Richard Hughes and others circa 2009-2010  (e.g. 
http://comments.gmane.org/gmane.comp.freedesktop.xorg/41559, 
http://lists.x.org/archives/xorg-devel/2010-July/010922.html) Then 
discussion of this topic seems to die.

All this leads me to think that there's something fundamentally 
problematic about using DDC/CI in Linux.   Is that the case, or is there 
a solution that I've overlooked?  If no general solution is possible, is 
there at least a path for me to cobble together something that works for 
my specific monitors and systems?

Sanford