>Yeah, the nVidia driver is annoying ... it used to work and they broke
>it a few years ago and they don't care enough to fix it.
>And since I got a new laptop a few years back, I don't have a nvidia
>card to debug or work around it.

I compared fosphor to the nVidia OpenCL Simple OpenGL Interop example [1] and noticed that fosphor calls glMapBuffer/glUnmapBuffer to clear the spectrum vbo between the calls to glBufferData and clCreateFromGLBuffer.  If I eliminate the map/memset/unmap here by removing  the call to gl_vbo_clear in gl_deferred_init [2], then clCreateFromGLBuffer returns CL_SUCCESS and fosphor appears to work with CL/GL sharing.  It is not clear to me if clearing the vbo_spectrum is necessary here, since cl_queue_clear_buffers later initializes the  mem_spectrum buffer to the noise floor.

I'm using an nvidia GTX 1650 with version 430.50 of the nvidia drivers under Linux Mint 18.  A  friend of mine tested the GTX 1060 and also had  success with this workaround.

Aaron

[1]
http://developer.download.nvidia.com/compute/DevZone/OpenCL/Projects/oclSimpleGL.tar.gz

[2]
https://git.osmocom.org/gr-fosphor/tree/lib/fosphor/gl.c#n235