[Mesa-dev] [Piglit] [PATCH 1/2] egl: Add sanity test for EGL_EXT_device_query (v3)

[Kyle Brenneman]

On 09/06/2016 05:29 AM, Emil Velikov wrote:
> * Interaction of ^^ with EGL device extension(s) - update existing
> extensions/introduce new ones
>   ** Should EGL_EXT_device_enumeration expose one/multiple SW devices
>   - no: we need alternative glvnd EGL interface for such cases
>   - yes: implementing EGL_EXT_output_drm on EGL implementations
> supporting both HW and SW devices is close to impossible barring spec
> update
>
(Trimming other bullet points for readability)

GLVND itself can support EGL_EXT_device_enumeration, but it doesn't 
require any vendor library to support it. It'll advertise 
EGL_EXT_device_enumeration to the application if and only if at least 
one vendor advertises it, and then for eglQueryDevicesEXT, it will just 
call into each vendor library that supports it and concatenate the 
vendor's lists together. If a vendor doesn't support 
EGL_EXT_device_enumeration, then GLVND will just skip it and it won't be 
included in the eglQueryDevicesEXT list.

 From a driver's perspective, the only requirement that GLVND adds is 
that the EGLDeviceEXT handles have to be pointers to some address that 
the vendor library somehow controls. That's only to ensure that the 
handles are unique between vendors, so GLVND doesn't care what (if 
anything) it actually points to. Other than that, the same 
implementation of eglQueryDevicesEXT should work with or without GLVND.

-Kyle