drm/debugfs: add a "force" file per connector

Add a file to debugfs for each connector to enable modification of the
"force" connector attribute. This allows connectors to be enabled or
disabled for testing and debugging purposes.

v2: Add stricter value checking and clean up debugfs_entry if file
    creation fails in drm_debugfs_connector_add. (David Herrmann)

Signed-off-by: Thomas Wood <thomas.wood@intel.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

include/drm/drmP.h

@@ -1419,6 +1419,8 @@ extern int drm_debugfs_create_files(const struct drm_info_list *files,
 extern int drm_debugfs_remove_files(const struct drm_info_list *files,
 				    int count, struct drm_minor *minor);
 extern int drm_debugfs_cleanup(struct drm_minor *minor);
+extern int drm_debugfs_connector_add(struct drm_connector *connector);
+extern void drm_debugfs_connector_remove(struct drm_connector *connector);
 #else
 static inline int drm_debugfs_init(struct drm_minor *minor, int minor_id,
 				   struct dentry *root)
@@ -1443,6 +1445,15 @@ static inline int drm_debugfs_cleanup(struct drm_minor *minor)
 {
 	return 0;
 }
+
+static inline int drm_debugfs_connector_add(struct drm_connector *connector)
+{
+	return 0;
+}
+static inline void drm_debugfs_connector_remove(struct drm_connector *connector)
+{
+}
+
 #endif
 
 				/* Info file support */