1. Are you attempting to "debug" clinfo through CodeXL or "profile" it? What happens if you do the other?
2. In CodeXL's System information dialog, do all OpenCL devices appear, or only the one attached to the main display?
3. One thing that might work would be to run "amdconfig --initial --adapter=all" (and any other changes you made to xorg.conf since the last time you ran [amd|ati]config --initial might need to be re-applied).
4. If that fails, as a workaround, you might not need to change xorg.conf, try going into the project settings dialog, and in the "environment" field, add the variable DISPLAY, with the value ":X" or ":X.Y" where X is the display index and Y is the screen index. To switch GPUs you would probably need to set ":1" or ":1.0". (You can also check the index for your current screen in the console by typing "set | grep DISPLAY").
4'. If you want to keep the main desktop but use the other GPU for OpenCL, you might want to try to set the variable COMPUTE to the display identifier (same format as above). I think if DISPLAY is present it overrides COMPUTE, so you might need to unset that value as well.
We are setting up a multiple-display system in our labs to recreate your issue - any other information about your system (e.g. OS distro / version) could be useful.
Uri, ultimately I am very busy now and I do not have time to dig into this. AMD should check it and fix it. In the past I have followed many instructions to collect data by requests from AMD forums etc. and many of the problems I reported still exist. (meanwhile on Nvidia platform, none of those problems existed, including this problem). I feel like my time is wasted also. You should report this issue to developers and get it fixed in the next driver version. As simple as that, by the way, one other problem is that (which I reported earlier but) CodeXL does not work over ssh connection if the client does not have an AMD GPU. Almost nobody has an AMD GPU in their laptops etc. because there are not any reasonably featured AMD laptops on sale (I mean most AMD laptops have only HD resolution, 1366 x 768, with 15-17" screen which is very bad for developers who look at text so nobody wants them). So, the bottom line is that it is impossible to develop software on AMD hardware.
I know from experience that if a GPU is not in the X config then it wont appear if COMPUTE is set even for running programs.
I also tried making xorg configurations for monitors on 1st card only, monitors on 2nd card only, and monitors on both cards (multi-desktop) and nothing works.
I just do not have time to test other combinations now as also the machine is in use and we do not want to mess with the configuration.
Uri, I am very busy right now. The system was Ubuntu 14.04 with OMEGA drivers. I will reply to your advices when I have time to test them.