[PATCH 1/2] Revert "drm: hide unregistered connectors from GETCONNECTOR IOCTL"

[Ville Syrjälä]

On Tue, Oct 18, 2022 at 11:27:19AM +0200, Jonas Ådahl wrote:
> On Tue, Oct 18, 2022 at 12:14:09PM +0300, Ville Syrjälä wrote:
> > On Mon, Oct 17, 2022 at 03:31:57PM +0000, Simon Ser wrote:
> > > This reverts commit 981f09295687f856d5345e19c7084aca481c1395.
> > > 
> > > It turns out this breaks Mutter.
> > 
> > A bit more detail would be a good to help future archaeologists.
> 
> Perhaps a better explanation is
> 
> It turns out this causes logically active but disconnected MST display
> port connectors to disappear from the drmModeGetResources() list,

That was the whole point was it not? So I'd drop the
"it turns out" part.

> meaning userspace is made to believe the connector is already disabled.

That wording to me implies its a generic issue affecting all
userspace when so far it looks like only mutter is affected.
So apparently mutter (for some reason) assumes that the
connector has somehow magically been disabled by someone
else if it disappears from the list of resources?

> 
> When userspace then attempts post a new mode set commit, if that commit
> uses the same CRTC used to previously drive the disconnected connector,
> it will fail as that CRTC is logically still tied to the disconnected
> connector.
> 
> This was discovered by a bisecting docking station hot plugging
> regression using mutter.
> 
> 
> Jonas
> 
> > 
> > > 
> > > Signed-off-by: Simon Ser <contact at emersion.fr>
> > > Cc: Daniel Vetter <daniel.vetter at ffwll.ch>
> > > Cc: Lyude Paul <lyude at redhat.com>
> > > Cc: Jonas Ådahl <jadahl at redhat.com>
> > > ---
> > >  drivers/gpu/drm/drm_mode_config.c | 3 ---
> > >  1 file changed, 3 deletions(-)
> > > 
> > > diff --git a/drivers/gpu/drm/drm_mode_config.c b/drivers/gpu/drm/drm_mode_config.c
> > > index 939d621c9ad4..688c8afe0bf1 100644
> > > --- a/drivers/gpu/drm/drm_mode_config.c
> > > +++ b/drivers/gpu/drm/drm_mode_config.c
> > > @@ -151,9 +151,6 @@ int drm_mode_getresources(struct drm_device *dev, void *data,
> > >  	count = 0;
> > >  	connector_id = u64_to_user_ptr(card_res->connector_id_ptr);
> > >  	drm_for_each_connector_iter(connector, &conn_iter) {
> > > -		if (connector->registration_state != DRM_CONNECTOR_REGISTERED)
> > > -			continue;
> > > -
> > >  		/* only expose writeback connectors if userspace understands them */
> > >  		if (!file_priv->writeback_connectors &&
> > >  		    (connector->connector_type == DRM_MODE_CONNECTOR_WRITEBACK))
> > > -- 
> > > 2.38.0
> > > 
> > 
> > -- 
> > Ville Syrjälä
> > Intel
> > 

-- 
Ville Syrjälä
Intel