drm: add drm_get_connector_force_name

Follow the naming in debugfs also for logging, add "unknown" for values
beyond the enumerated ones.

v2: add \n in connector_show, make internal to drm (Chris)

Cc: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1487580708-29340-1-git-send-email-jani.nikula@intel.com
diff --git a/drivers/gpu/drm/drm_connector.c b/drivers/gpu/drm/drm_connector.c
index ab73e86..76ea30c 100644
--- a/drivers/gpu/drm/drm_connector.c
+++ b/drivers/gpu/drm/drm_connector.c
@@ -128,22 +128,8 @@
 		return;
 
 	if (mode->force) {
-		const char *s;
-
-		switch (mode->force) {
-		case DRM_FORCE_OFF:
-			s = "OFF";
-			break;
-		case DRM_FORCE_ON_DIGITAL:
-			s = "ON - dig";
-			break;
-		default:
-		case DRM_FORCE_ON:
-			s = "ON";
-			break;
-		}
-
-		DRM_INFO("forcing %s connector %s\n", connector->name, s);
+		DRM_INFO("forcing %s connector %s\n", connector->name,
+			 drm_get_connector_force_name(mode->force));
 		connector->force = mode->force;
 	}
 
@@ -492,6 +478,28 @@
 }
 EXPORT_SYMBOL(drm_get_connector_status_name);
 
+/**
+ * drm_get_connector_force_name - return a string for connector force
+ * @force: connector force to get name of
+ *
+ * Returns: const pointer to name.
+ */
+const char *drm_get_connector_force_name(enum drm_connector_force force)
+{
+	switch (force) {
+	case DRM_FORCE_UNSPECIFIED:
+		return "unspecified";
+	case DRM_FORCE_OFF:
+		return "off";
+	case DRM_FORCE_ON:
+		return "on";
+	case DRM_FORCE_ON_DIGITAL:
+		return "digital";
+	default:
+		return "unknown";
+	}
+}
+
 #ifdef CONFIG_LOCKDEP
 static struct lockdep_map connector_list_iter_dep_map = {
 	.name = "drm_connector_list_iter"