1 files changed, 69 insertions, 2 deletions

diff --git a/include/drm/drm_connector.h b/include/drm/drm_connector.h
index 91a877fa00cb..9ccad6b062f2 100644
--- a/include/drm/drm_connector.h
+++ b/include/drm/drm_connector.h
@@ -82,6 +82,53 @@ enum drm_connector_status {
 	connector_status_unknown = 3,
 };
 
+/**
+ * enum drm_connector_registration_status - userspace registration status for
+ * a &drm_connector
+ *
+ * This enum is used to track the status of initializing a connector and
+ * registering it with userspace, so that DRM can prevent bogus modesets on
+ * connectors that no longer exist.
+ */
+enum drm_connector_registration_state {
+	/**
+	 * @DRM_CONNECTOR_INITIALIZING: The connector has just been created,
+	 * but has yet to be exposed to userspace. There should be no
+	 * additional restrictions to how the state of this connector may be
+	 * modified.
+	 */
+	DRM_CONNECTOR_INITIALIZING = 0,
+
+	/**
+	 * @DRM_CONNECTOR_REGISTERED: The connector has been fully initialized
+	 * and registered with sysfs, as such it has been exposed to
+	 * userspace. There should be no additional restrictions to how the
+	 * state of this connector may be modified.
+	 */
+	DRM_CONNECTOR_REGISTERED = 1,
+
+	/**
+	 * @DRM_CONNECTOR_UNREGISTERED: The connector has either been exposed
+	 * to userspace and has since been unregistered and removed from
+	 * userspace, or the connector was unregistered before it had a chance
+	 * to be exposed to userspace (e.g. still in the
+	 * @DRM_CONNECTOR_INITIALIZING state). When a connector is
+	 * unregistered, there are additional restrictions to how its state
+	 * may be modified:
+	 *
+	 * - An unregistered connector may only have its DPMS changed from
+	 *   On->Off. Once DPMS is changed to Off, it may not be switched back
+	 *   to On.
+	 * - Modesets are not allowed on unregistered connectors, unless they
+	 *   would result in disabling its assigned CRTCs. This means
+	 *   disabling a CRTC on an unregistered connector is OK, but enabling
+	 *   one is not.
+	 * - Removing a CRTC from an unregistered connector is OK, but new
+	 *   CRTCs may never be assigned to an unregistered connector.
+	 */
+	DRM_CONNECTOR_UNREGISTERED = 2,
+};
+
 enum subpixel_order {
 	SubPixelUnknown = 0,
 	SubPixelHorizontalRGB,
@@ -853,10 +900,12 @@ struct drm_connector {
 	bool ycbcr_420_allowed;
 
 	/**
-	 * @registered: Is this connector exposed (registered) with userspace?
+	 * @registration_state: Is this connector initializing, exposed
+	 * (registered) with userspace, or unregistered?
+	 *
 	 * Protected by @mutex.
 	 */
-	bool registered;
+	enum drm_connector_registration_state registration_state;
 
 	/**
 	 * @modes:
@@ -1166,6 +1215,24 @@ static inline void drm_connector_unreference(struct drm_connector *connector)
 	drm_connector_put(connector);
 }
 
+/**
+ * drm_connector_is_unregistered - has the connector been unregistered from
+ * userspace?
+ * @connector: DRM connector
+ *
+ * Checks whether or not @connector has been unregistered from userspace.
+ *
+ * Returns:
+ * True if the connector was unregistered, false if the connector is
+ * registered or has not yet been registered with userspace.
+ */
+static inline bool
+drm_connector_is_unregistered(struct drm_connector *connector)
+{
+	return READ_ONCE(connector->registration_state) ==
+		DRM_CONNECTOR_UNREGISTERED;
+}
+
 const char *drm_get_connector_status_name(enum drm_connector_status status);
 const char *drm_get_subpixel_order_name(enum subpixel_order order);
 const char *drm_get_dpms_name(int val);