It’s been a while that Igalia’s graphics team had been working on the OpenGL extensions that provide the mechanisms for OpenGL and Vulkan interoperability in the Intel iris (gallium3d) driver that is part of mesa.
As there were no conformance tests (CTS) for this extension, and we needed to test it, we have written (and we are still writing) small tests for piglit that allow the exchange and the synchronization of the exchange of resources such as buffers, textures, and depth or stencil buffers.
This was difficult because not only most drivers were untested (and it was tricky to tell if there’s a bug or we don’t use the extension properly) but also, there were no interoperability examples out there to use them as a reference. We had to use debugging hacks like for example writing the tests in OpenGL first, then in Vulkan, and then in both using interoperability to reach a conclusion about how the extension should be used and if the driver is implementing it correctly.
So, after having spent some time trying to understand the interoperability extensions, I thought that it might be useful to start a series of posts on how to use them on Linux for different cases (eg: exchange a texture, a depth buffer, a stencil buffer, a pixel buffer and so on), using the small tests I’ve written for piglit as example. The full code can be found in the piglit repository, although some of the examples might not be there yet as they’re under review at the time of writing.