This is easy to reproduce.
1. Install ArgyllCMS 0.60 or later. There is an autotooled version on the ArgyllCMS web site located here http://www.argyllcms.com/downloadsrc.html
. If you are a Gentoo user there is also an ebuild.
2. After installing ArgyllCMS on a TwinView machine run:
# dispwin -r
This program is the LUT loader that is part of ArgyllCMS and the -r parm will normally cause dispwin to generate a report of the displays on the system. In TwinView it will fail with the following messages:
X Error of failed request: BadValue (integer parameter out of range for operation)
Major opcode of failed request: 135 (XFree86-VidModeExtension)
Minor opcode of failed request: 4 (XF86VidModeGetMonitor)
Value in failed request: 0x135
Serial number of failed request: 12
Current serial number in output stream: 12
When I asked the author of ArgyllCMS about this his reply was:
"In any case, it seems that yes, TwinView and MergeFB both have the facility to emulate Xinerama to provide the hints needed for applications to position windows intelligently, but both fail to implement the XFree86-VidModeExtension in a way that allows access to the Video LUTs of the underlying screens.
I will modify dispwin to avoid the X error that occurs when just scanning for the different screens, but I will simply be
recommending that anyone who wants to have color calibrated displays on Linux/X11 not use TwinView or MergeFB."
I have attached a nvidia-bug-report.log file.