drm/panel: Let of_drm_find_panel() return -ENODEV when the panel is disabled

DT nodes might be present in the DT but with a status property set to
"disabled" or "fail". In this case, we should not return -EPROBE_DEFER
when the caller asks for a drm_panel instance. Return -ENODEV instead.
Signed-off-by: Boris Brezillon <boris.brezillon@bootlin.com>
Reviewed-by: Thierry Reding <treding@nvidia.com>
Acked-by: Thierry Reding <treding@nvidia.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180509130042.9435-3-boris.brezillon@bootlin.com

drivers/gpu/drm/drm_panel.c

@@ -152,13 +152,18 @@ EXPORT_SYMBOL(drm_panel_detach);
  *
  * Return: A pointer to the panel registered for the specified device tree
  * node or an ERR_PTR() if no panel matching the device tree node can be found.
- * The only error that can be reported is -EPROBE_DEFER, meaning that the panel
- * device has not been probed yet, and the caller should retry later.
+ * Possible error codes returned by this function:
+ * - EPROBE_DEFER: the panel device has not been probed yet, and the caller
+ *   should retry later
+ * - ENODEV: the device is not available (status != "okay" or "ok")
  */
 struct drm_panel *of_drm_find_panel(const struct device_node *np)
 {
 	struct drm_panel *panel;
 
+	if (!of_device_is_available(np))
+		return ERR_PTR(-ENODEV);
+
 	mutex_lock(&panel_lock);
 
 	list_for_each_entry(panel, &panel_list, list) {