leds: Add common LED binding parsing support to LED class/core

Qucik grep for 'for_each' or 'linux,default-trigger' or
'default-state' under drivers/leds can tell quite a lot. It seems
multiple LED controller drivers implement the very similar looping
through the child nodes in order to locate the LED nodes and read
and support the common LED dt bindings. Implementing this same
stuff for all LED controllers gets old pretty fast.

This commit adds support for locating the LED node (based on known
node names - or linux,led-compatible property) and handling of
few common LED properties.

linux,default-trigger,
default-state (with the exception of keep),

(in addition to already handled
function-enumerator,
function,
color
and label).

Regarding the node look-up: If no init_data is given, then no
node-lookup is done and cdev name is used as such.

If init_data is goven but no starting point for node lookup - then
(parent) device's own DT node is used. If no led-compatible is given,
then of_match is searched for. If neither led-compatible not of_match
is given then device's own node or passed starting point are used as
such.

Signed-off-by: Matti Vaittinen <matti.vaittinen@fi.rohmeurope.com>

drivers/leds/led-class.c

@@ -235,6 +235,29 @@ static int led_classdev_next_name(const char *init_name, char *name,
 	return i;
 }
 
+static void led_add_props(struct led_classdev *ld, struct led_properties *props)
+{
+	if (props->default_trigger)
+		ld->default_trigger = props->default_trigger;
+	/*
+	 * According to binding docs the LED is by-default turned OFF unless
+	 * default_state is used to indicate it should be ON or that state
+	 * should be kept as is
+	 */
+	if (props->default_state) {
+		ld->brightness = LED_OFF;
+		if (!strcmp(props->default_state, "on"))
+			ld->brightness = LED_FULL;
+	/*
+	 * We probably should not call the brightness_get prior calling
+	 * the of_parse_cb if one is provided.
+	 * Add a flag to advertice that state should be queried and kept as-is.
+	 */
+		else if (!strcmp(props->default_state, "keep"))
+			props->brightness_keep = true;
+	}
+}
+
 /**
  * led_classdev_register_ext - register a new object of led_classdev class
  *			       with init data.
@@ -251,45 +274,87 @@ int led_classdev_register_ext(struct device *parent,
 	char final_name[LED_MAX_NAME_SIZE];
 	const char *proposed_name = composed_name;
 	int ret;
-
+	struct led_properties props = {0};
+	struct fwnode_handle *fw;
+
+	/*
+	 * We don't try getting the name based on DT node if init-data is not
+	 * given. We could see if we find LED properties from the device's node
+	 * but that might change LED names for old users of
+	 * led_classdev_register who have been providing the LED name in
+	 * cdev->name. So we seek fwnode for names only if init_data is given
+	 */
 	if (init_data) {
+		led_cdev->init_data = init_data;
 		if (init_data->devname_mandatory && !init_data->devicename) {
 			dev_err(parent, "Mandatory device name is missing");
 			return -EINVAL;
 		}
-		ret = led_compose_name(parent, init_data, composed_name);
+
+		fw = led_find_fwnode(parent, init_data);
+		if (!fw) {
+			dev_err(parent, "No fwnode found\n");
+			return -ENOENT;
+		}
+		/*
+		 * We did increase refcount for fwnode. Let's set a flag so we
+		 * can decrease it during deregistration
+		 */
+		led_cdev->fwnode_owned = true;
+
+		ret = led_parse_fwnode_props(parent, fw, &props);
+		if (ret)
+			goto err_out;
+
+		if (init_data->of_parse_cb)
+			ret = init_data->of_parse_cb(led_cdev, fw, &props);
 		if (ret < 0)
-			return ret;
+			goto err_out;
+
+		led_add_props(led_cdev, &props);
+
+		ret = led_compose_name(parent, init_data, &props,
+				       composed_name);
+		if (ret < 0)
+			goto err_out;
 	} else {
 		proposed_name = led_cdev->name;
+		led_cdev->fwnode_owned = false;
+		fw = NULL;
 	}
 
 	ret = led_classdev_next_name(proposed_name, final_name, sizeof(final_name));
 	if (ret < 0)
-		return ret;
+		goto err_out;
 
 	mutex_init(&led_cdev->led_access);
 	mutex_lock(&led_cdev->led_access);
 	led_cdev->dev = device_create_with_groups(leds_class, parent, 0,
 				led_cdev, led_cdev->groups, "%s", final_name);
 	if (IS_ERR(led_cdev->dev)) {
 		mutex_unlock(&led_cdev->led_access);
-		return PTR_ERR(led_cdev->dev);
+		ret = PTR_ERR(led_cdev->dev);
+		goto err_out;
 	}
-	if (init_data && init_data->fwnode)
-		led_cdev->dev->fwnode = init_data->fwnode;
+	if (fw)
+		led_cdev->dev->fwnode = fw;
 
 	if (ret)
 		dev_warn(parent, "Led %s renamed to %s due to name collision",
 				led_cdev->name, dev_name(led_cdev->dev));
 
+	if (props.brightness_keep)
+		if (led_cdev->brightness_get)
+			led_cdev->brightness =
+				 led_cdev->brightness_get(led_cdev);
+
 	if (led_cdev->flags & LED_BRIGHT_HW_CHANGED) {
 		ret = led_add_brightness_hw_changed(led_cdev);
 		if (ret) {
 			device_unregister(led_cdev->dev);
 			led_cdev->dev = NULL;
 			mutex_unlock(&led_cdev->led_access);
-			return ret;
+			goto err_out;
 		}
 	}
 
@@ -322,6 +387,10 @@ int led_classdev_register_ext(struct device *parent,
 			led_cdev->name);
 
 	return 0;
+err_out:
+	if (led_cdev->fwnode_owned)
+		fwnode_handle_put(fw);
+	return ret;
 }
 EXPORT_SYMBOL_GPL(led_classdev_register_ext);
 
@@ -355,6 +424,9 @@ void led_classdev_unregister(struct led_classdev *led_cdev)
 	if (led_cdev->flags & LED_BRIGHT_HW_CHANGED)
 		led_remove_brightness_hw_changed(led_cdev);
 
+	if (led_cdev->fwnode_owned)
+		fwnode_handle_put(led_cdev->dev->fwnode);
+
 	device_unregister(led_cdev->dev);
 
 	down_write(&leds_list_lock);