[Mesa-dev] [PATCH] [rfc] radv: add initial prime support.

[Dave Airlie]

On 23 November 2016 at 21:13, Mike Lothian <mike at fireburn.co.uk> wrote:
> I think it would be good to keep the DRI_PRIME switch to allow for switching
> between anvil and radv, handy for testing / comparing / benchmarking both
>
> It seems that Vulkan automatically uses the first card listed in vulkaninfo
> (in my case it's the amdgpu card) with no way to select which is used, hence
> why I've only been seeing garbage since the radv driver was added into mesa
>
> If DRI_PRIME=0 is passed will this now automatically use anvil?
>
Unfortunately DRI_PRIME semantics won't work with vulkan at all, what I've done
here is a pretty big hack.

The problem is the generic vulkan loader loads all the available ICDs,
which enumerate all
the devices themselves. So in theory to make DRI_PRIME work I'd have to change
the loader, but using DRI_PRIME in the loader doesn't make much sense,
even less sense is using the ID tag unfortunately, as the loader has
no such knowledge.

I'm contemplating making a vulkan layer to reorder the output from
enumeration along
with some user selected env var (ideally apps would do this).

So I doubt the actual answer is going to involve DRI_PRIME working
with vulkan at all
unfortunately.

Dave.