[PATCH] unstable/drm-lease: DRM lease protocol support

[Simon Ser]

On Friday, June 28, 2019 12:23 PM, Philipp Zabel <p.zabel at pengutronix.de> wrote:
> > I'm not sure the client is in the best position to decide which connectors to
> > pick here.
>
> The client may be the only one with enough knowledge to pick, see below.
>
> > Maybe it would be better for the client to say why it needs a lease (e.g. it
> > needs the non-desktop connectors for VR) and let the compositor pick appropriate
> > connectors.
>
> How then would the desktop compositor decide which of the non-desktop
> connectors the client requires?
>
> For example, if I have two simultaneously connected VR headsets, each
> running their own VR client, how would the two clients each lease only
> the non-desktop connector corresponding to their headset?

[…]

> > If the compositor advertizes both non-desktop outputs (for VR) and
> > desktop outputs (for games), how should the VR client pick the right
> > output?
>
> Depending on the hardware and setup, the VR client may match the serial
> number contained in the EDID with one retrieved via USB to identify the
> correct connector to render to a given VR headset, or it may just
> compare the vendor and product id. In a CAVE setup the client may have
> manual configuration telling it which projectors to render to, so I
> think the client needs access to at least the uniquely identifying parts
> of the EDID.

Indeed, that makes sense. So another idea that was floating around
would be to allow the client to get a lease FD with zero leased
resources, let it inspect the connectors via DRM properties, then
let the client request a particular connector ID and get a second
lease.

We could also expose make/model/serial instead. In any case, the
connector name probably won't help a lot.