i915/display/hotplug: use drm_kms_helper_connector_hotplug_event()

This adds more information to the hotplug uevent and lets user-space
know that it's about a particular connector only.

v2: don't rely on the changed HPD pin bitmask to count changed
    connectors (Jani)
Signed-off-by: Simon Ser <contact@emersion.fr>
Cc: Jani Nikula <jani.nikula@intel.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Cc: Gustavo Sousa <gustavo.sousa@intel.com>
Cc: Imre Deak <imre.deak@intel.com>
Cc: Lucas De Marchi <lucas.demarchi@intel.com>
Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230623094229.120264-1-contact@emersion.fr

drivers/gpu/drm/i915/display/intel_hotplug.c

@@ -376,6 +376,8 @@ static void i915_hotplug_work_func(struct work_struct *work)
 	u32 changed = 0, retry = 0;
 	u32 hpd_event_bits;
 	u32 hpd_retry_bits;
+	struct drm_connector *first_changed_connector = NULL;
+	int changed_connectors = 0;
 
 	mutex_lock(&dev_priv->drm.mode_config.mutex);
 	drm_dbg_kms(&dev_priv->drm, "running encoder hotplug functions\n");
@@ -428,6 +430,11 @@ static void i915_hotplug_work_func(struct work_struct *work)
 				break;
 			case INTEL_HOTPLUG_CHANGED:
 				changed |= hpd_bit;
+				changed_connectors++;
+				if (!first_changed_connector) {
+					drm_connector_get(&connector->base);
+					first_changed_connector = &connector->base;
+				}
 				break;
 			case INTEL_HOTPLUG_RETRY:
 				retry |= hpd_bit;
@@ -438,9 +445,14 @@ static void i915_hotplug_work_func(struct work_struct *work)
 	drm_connector_list_iter_end(&conn_iter);
 	mutex_unlock(&dev_priv->drm.mode_config.mutex);
 
-	if (changed)
+	if (changed_connectors == 1)
+		drm_kms_helper_connector_hotplug_event(first_changed_connector);
+	else if (changed_connectors > 0)
 		drm_kms_helper_hotplug_event(&dev_priv->drm);
 
+	if (first_changed_connector)
+		drm_connector_put(first_changed_connector);
+
 	/* Remove shared HPD pins that have changed */
 	retry &= ~changed;
 	if (retry) {