[PATCH v6] unstable/drm-lease: DRM lease protocol support

Simon Ser contact at emersion.fr
Tue Sep 3 06:47:41 UTC 2019

On Tuesday, September 3, 2019 1:15 AM, Sebastian Wick <sebastian at sebastianwick.net> wrote:

> On 2019-07-30 14:53, Drew DeVault wrote:
> > From: Marius Vlad marius.vlad at collabora.com
> > DRM leasing is a feature which allows the DRM master to "lease" a
> > subset
> > of its DRM resources to another DRM master via drmModeCreateLease,
> > which
> > returns a file descriptor for the new DRM master. We use this protocol
> > to negotiate the terms of the lease and transfer this file descriptor
> > to
> > clients.
> > In less DRM-specific terms: this protocol allows Wayland compositors to
> > give over their GPU resources (like displays) to a Wayland client to
> > exclusively control.
> > The primary use-case for this is Virtual Reality headsets, which via
> > the
> > non-desktop DRM property are generally not used as desktop displays by
> > Wayland compositors, and for latency reasons (among others) are most
> > useful to games et al if they have direct control over the DRM
> > resources
> > associated with it. Basically, these are peripherals which are of no
> > use
> > to the compositor and may be of use to a client, but since they are
> > tied
> > up in DRM we need to use DRM leasing to get them into client's hands.
> Talking about use-cases, I'm evaluating leasing for display calibration
> and profiling which requires leasing outputs which are are part of the
> desktop and also requires user interaction (keyboard, mice). Are there
> any ideas on how something like that would work?
> I think it would be great if it worked similar to fullscreen surfaces
> but input handling depends on having a surface but leasing an output is
> independent.

I'd rather not use DRM leasing for this. See the earlier discussions
about DRM leasing use-cases.

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