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

["Jonas Ådahl" <jadahl@redhat.com>]

On Mon, Oct 17, 2022 at 03:32:01PM +0000, Simon Ser wrote:
> 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@emersion.fr>
> Cc: stable@vger.kernel.org
> Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
> Cc: Lyude Paul <lyude@redhat.com>
> Cc: Jonas Ådahl <jadahl@redhat.com>

Tested-by: Jonas Ådahl <jadahl@redhat.com>


Jonas