rendering scene on a card different from the one displaying

[Konstantin Kharlamov]

On Thu, 2024-01-25 at 18:13 +0300, test wrote:
> What is the most proper way to re-route output from a rendering card 
> (which can have it's output disconnected or don't have it at all) to
> a 
> displaying card (weak one, iGPU etc)?
> For example, a laptop with an external card in an ExpressCard riser
> (no 
> external display is connected to the card), or a desktop PC with 
> embedded video plus Nvidia Tesla?
> How should I configure Mesa in order to get «auto-screen-grabbing»
> from 
> the rendering card to the displaying one?

Fixed the title.

Sounds like you're interested in `DRI_PRIME` variable. See
documentation here
https://docs.mesa3d.org/envvars.html#envvar-DRI_PRIME

Assuming you want this for development purposes, you can also use
Vulkan API, but Idk details here.

This is a user question though, so belongs to mesa-users and not to
mesa-dev.