1 files changed, 26 insertions, 0 deletions
diff --git a/drivers/gpu/drm/drm_connector.c b/drivers/gpu/drm/drm_connector.c
index f2b20fd66319..7a6779cab12f 100644
--- a/drivers/gpu/drm/drm_connector.c
+++ b/drivers/gpu/drm/drm_connector.c
@@ -994,6 +994,32 @@ static const struct drm_prop_enum_list dp_colorspaces[] = {
  *      after modeset, the kernel driver may set this to "BAD" and issue a
  *      hotplug uevent. Drivers should update this value using
  *      drm_connector_set_link_status_property().
+ *
+ *      When user-space receives the hotplug uevent and detects a "BAD"
+ *      link-status, the sink doesn't receive pixels anymore (e.g. the screen
+ *      becomes completely black). The list of available modes may have
+ *      changed. User-space is expected to pick a new mode if the current one
+ *      has disappeared and perform a new modeset with link-status set to
+ *      "GOOD" to re-enable the connector.
+ *
+ *      If multiple connectors share the same CRTC and one of them gets a "BAD"
+ *      link-status, the other are unaffected (ie. the sinks still continue to
+ *      receive pixels).
+ *
+ *      When user-space performs an atomic commit on a connector with a "BAD"
+ *      link-status without resetting the property to "GOOD", the sink may
+ *      still not receive pixels. When user-space performs an atomic commit
+ *      which resets the link-status property to "GOOD" without the
+ *      ALLOW_MODESET flag set, it might fail because a modeset is required.
+ *
+ *      User-space can only change link-status to "GOOD", changing it to "BAD"
+ *      is a no-op.
+ *
+ *      For backwards compatibility with non-atomic userspace the kernel
+ *      tries to automatically set the link-status back to "GOOD" in the
+ *      SETCRTC IOCTL. This might fail if the mode is no longer valid, similar
+ *      to how it might fail if a different screen has been connected in the
+ *      interim.
  * non_desktop:
  * 	Indicates the output should be ignored for purposes of displaying a
  * 	standard desktop environment or console. This is most likely because