libweston as a DRM lease lessee

[Pekka Paalanen]

On Mon, 1 Feb 2021 18:19:29 +0900
Damian Hobson-Garcia <dhobsong at igel.co.jp> wrote:

> Hi all,
> 
> I am working on adding DRM lease support to a libweston based compositor.
> The compositor will be a client (lessee) that will display output to a 
> DRM lease that
> is created by another (lessor) process, so this is kind of the opposite 
> direction to the DRM lease patches
> that were submitted a while back [1].
> 
> The motivation is to be able to run multiple instances of weston w/ DRM 
> backend, where each instance
> has direct access to a subset of the DRM connectors.  Each instance 
> could, for example, run in a separate container,
> with minimal host interaction.
> 
> In this configuration the DRM lease would be received from a UNIX domain 
> socket connection to the lessor,
> so would not discoverable via udev, in the same way that DRM device 
> nodes normally are.
> 
> I think that I would need to make changes to the compositor-drm, but if 
> possible,
> I'd like to make those changes generic enough to be useful upstream as 
> well, so I was hoping to get some feedback before possibly heading down 
> a wrong path.

Hi,

that is an interesting goal. How will this "nested" Weston/DRM get
input?

>  From what I can tell, I need to:
> 
> 1. Get the DRM lease file descriptor, given an identifier (In my DRM 
> lease case this is a name that maps to a socket path)
> 2. Get a udev_device struct for the device corresponding to the above fd 
> (via the major:minor numbers)
> 
> I think that #1 can be implemented in either via the launcher API (a new 
> launcher type?) or by adding an option for
> the compositor to provide the fd, but #2 seems like it should be in 
> compositor-drm, right?

Hmm, what would an udev_device be needed for? Hotplug events?


Thanks,
pq

> Are there other use cases that would benefit from extending the launcher 
> / compostior APIs in this way?
> or the udev device handle creation? Are there any plans/interest for 
> running the DRM backend from inside
> a container?
> 
> Thank you,
> Damian
> 
> [1] 
> https://lists.freedesktop.org/archives/wayland-devel/2018-February/037162.html
> 
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