[PATCH 2/2] drm/connector: send hotplug uevent on connector cleanup

[Simon Ser]

A typical DP-MST unplug removes a KMS connector. However care must
be taken to properly synchronize with user-space. The expected
sequence of events is the following:

1. The kernel notices that the DP-MST port is gone.
2. The kernel marks the connector as disconnected, then sends a
   uevent to make user-space re-scan the connector list.
3. User-space notices the connector goes from connected to disconnected,
   disables it.
4. Kernel handles the the IOCTL disabling the connector. On success,
   the very last reference to the struct drm_connector is dropped and
   drm_connector_cleanup() is called.
5. The connector is removed from the list, and a uevent is sent to tell
   user-space that the connector disappeared.

The very last step was missing. As a result, user-space thought the
connector still existed and could try to disable it again. Since the
kernel no longer knows about the connector, that would end up with
EINVAL and confused user-space.

Fix this by sending a hotplug uevent from drm_connector_cleanup().

Signed-off-by: Simon Ser <contact at emersion.fr>
Cc: stable at vger.kernel.org
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_connector.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/gpu/drm/drm_connector.c b/drivers/gpu/drm/drm_connector.c
index e3142c8142b3..90dad87e9ad0 100644
--- a/drivers/gpu/drm/drm_connector.c
+++ b/drivers/gpu/drm/drm_connector.c
@@ -582,6 +582,9 @@ void drm_connector_cleanup(struct drm_connector *connector)
 	mutex_destroy(&connector->mutex);
 
 	memset(connector, 0, sizeof(*connector));
+
+	if (dev->registered)
+		drm_sysfs_hotplug_event(dev);
 }
 EXPORT_SYMBOL(drm_connector_cleanup);
 
-- 
2.38.0