[PATCH 2/2] drm/connector: send hotplug uevent on connector cleanup
Jonas Ådahl
jadahl at redhat.com
Mon Oct 17 15:34:37 UTC 2022
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 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>
Tested-by: Jonas Ådahl <jadahl at redhat.com>
Jonas
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