Aliases for DRI connectors?

[Pekka Paalanen]

On Wed, 1 Apr 2020 14:38:37 -0500
Matt Hoosier <matt.hoosier at gmail.com> wrote:

> I'm searching for some sort of scheme that will let my DRI master query the
> set of available connectors and select the one carrying a prearranged
> designation. The problem I'm trying to solve is to allow deploying one
> standardized userspace component across a fleet of devices that have
> varying numbers of displays, with the use cases not always driven on the
> same connector topologically.
> 
> I had a look around the properties available on my system's DRI connectors,
> and nothing immediate jumped out at me. Is there a standard connector
> property that (assuming I can find the right place in DeviceTree or similar
> to) that would be a good fit for this?

Hi,

I've never heard of a thing that could accomplish that. DRM connector
names are not even actually communicated to userspace. What userspace
sees is connector type (enum) and some counter numbers (which are not
persistent, so not reliable if you have e.g. multiple DRM drivers
racing to initialize), and then userspace manufactures a connector name
from those. This has been most painful with Xorg, where the different
video DDX drivers used to use different conventions in making up the
names, meaning that if you switched DDXes (e.g. between driver-specific
driver and modesetting driver), the connector names changed
invalidating your xorg.conf.

However, the problem of non-persistent connector names has been thought
of, see e.g.:
https://lists.freedesktop.org/archives/dri-devel/2019-June/221902.html
The thread has messages also in July and August.

If you had reliable, persistent connector names (and used e.g. device
path from udev to reliably identify DRM devices), maybe you could build
something on top of that?

Though I doubt if maintainers would like your config to be in DT or
kernel, maybe it needs to be handled in userspace?


Thanks,
pq
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