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.
The required Vulkan implementation version for a Vkrunnershader test can now be specified in its [require] section. Tests that are targeting Vulkan versions that aren’t supported by the device driver will be skipped.
The video mostly shows the behavior of some GL calls and operations with and without the patches that improve the emulation of the ETC/EAC formats on Gen7 GPUs. The same programs run first with the previous ETC/EAC emulation (upper terminal) and then with the new one (lower terminal).
Sometimes, when working with the mesa drivers, modifying or replacing a shader might be extremely useful for debugging. Mesa allows users to replace their shaders at runtime without having to change the original code by providing these environment variables: