[PATCH v3 3/6] drm/connector: use drm_sysfs_connector_hotplug_event

[Simon Ser]

On Wednesday, October 27th, 2021 at 15:15, Pekka Paalanen <ppaalanen at gmail.com> wrote:

> On Fri, 15 Oct 2021 16:33:43 +0000
> Simon Ser <contact at emersion.fr> wrote:
>
> > In drm_connector_register, use drm_sysfs_connector_hotplug_event
> > instead of drm_sysfs_hotplug_event, because the hotplug event
> > only updates a single connector.
> >
> > Signed-off-by: Simon Ser <contact at emersion.fr>
> > ---
> >  drivers/gpu/drm/drm_connector.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/drivers/gpu/drm/drm_connector.c b/drivers/gpu/drm/drm_connector.c
> > index ec3973e8963c..a50c82bc2b2f 100644
> > --- a/drivers/gpu/drm/drm_connector.c
> > +++ b/drivers/gpu/drm/drm_connector.c
> > @@ -547,7 +547,7 @@ int drm_connector_register(struct drm_connector *connector)
> >  	connector->registration_state = DRM_CONNECTOR_REGISTERED;
> >
> >  	/* Let userspace know we have a new connector */
> > -	drm_sysfs_hotplug_event(connector->dev);
> > +	drm_sysfs_connector_hotplug_event(connector);
> >
> >  	if (connector->privacy_screen)
> >  		drm_privacy_screen_register_notifier(connector->privacy_screen,
>
> Hi Simon,
>
> this might not work for Weston if I understand this right. Kernel is
> adding a new connector, which means userspace does not recognise the
> connector id in the uevent. Weston as it is right now would ignore the
> event rather than add the connector.
>
> The missing piece is for Weston to revert to the old fashioned "recheck
> everything" behaviour when hotplug uevent carries anything
> unrecognised. Grep for drm_backend_update_conn_props if you want to see
> for yourself.
>
> However, I wouldn't NAK this patch just for Weston, but I wonder if
> other software would ignore events because of this as well.
>
> A whole another question is, would anyone notice. I guess this can only
> be an issue with MST.

I think Weston should be fine: udev_event_is_conn_prop_change returns false
if there's no PROPERTY in the uevent. An uevent with just a CONNECTOR and no
PROPERTY is something new. Weston already falls back to the old "reprobe the
world" approach in this case.

So far the CONNECTOR+PROPERTY uevent fields have only been used for content
protection stuff. I'm not aware of other user-space using it (checked Kodi
just in case, it doesn't do content protection nor handles uevents at all).

> All the other changes in this series look fine to me, so them I can give
> Acked-by: Pekka Paalanen <pekka.paalanen at collabora.com>

Thanks!