[systemd-devel] Ordering after udev applied rules to `/dev/dri/card0`

[Pekka Paalanen]

On Thu, 2 Apr 2020 10:35:49 +0300
Pekka Paalanen <ppaalanen at gmail.com> wrote:

> On Wed, 1 Apr 2020 17:09:59 +0200
> Lennart Poettering <mzxreary at 0pointer.de> wrote:
> 
> > On Mi, 01.04.20 11:34, Pekka Paalanen (ppaalanen at gmail.com) wrote:
> >   
> > > > > Is there a way to order a service in such a way, that it’s guaranteed that
> > > > > udev rules to devices were applied?
> > > > >
> > > > > A small script applying permissions and ownership manually in
> > > > > `ExecStartPre=` seems to work around the (graphics) issue.
> > > > >
> > > > > If it cannot be solved with ordering, what would you suggest?
> > > > >
> > > > > [1]: https://gitlab.freedesktop.org/wayland/weston/issues/382
> > > > > [2]: https://gitlab.freedesktop.org/wayland/weston/-/blob/master/libweston/backend-drm/kms.c#L741    
> > > >
> > > > Ideally Weston would just wait for devices assigned to the seat it
> > > > shall run on to appear to make this all safe.    
> > >
> > > Hi,
> > >
> > > there is an issue open about something like that:
> > > https://gitlab.freedesktop.org/wayland/weston/-/issues/173
> > >
> > > If I understand it right, waiting for CanGraphical allows Weston's
> > > DRM-backend to wait for any DRM device to appear on the seat, so that
> > > you don't need to hardcode in advance which DRM device to depend on.    
> > 
> > I don't think you need to wait for CanGraphical. I mean, the value of
> > that field just reflects whether at least one DRM or other graphical
> > device was discovered associated with the seat.  
> 
> Hi,
> 
> what other graphical devices than DRM devices? Or is that for the
> sysadmin to decide somehow?

Actually, seems like using CanGraphical was your idea:
https://gitlab.gnome.org/GNOME/gdm/issues/103

I guess things have changed in 7 years.

> What is CanGraphical useful for then? I've never really read about it,
> I only saw the GNOME Mutter MR and assumed it was a good idea.


Thanks,
pq
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