[PATCH v4 2/3] leds: pwm: Allow automatic labels for DT based devices

[Alexander Dahl <post@lespocky.de>]

If LEDs are configured through device tree and the property 'label' is
omitted, the label is supposed to be generated from the properties
'function' and 'color' if present.  While this works fine for e.g. the
'leds-gpio' driver, it did not for 'leds-pwm'.

The reason is, you get this label naming magic only if you add a LED
device through 'devm_led_classdev_register_ext()' and pass a pointer to
the current device tree node.

The approach to fix this requires a change to led-class checking on
init_data->fwnode being NULL early.

For the following node from dts the LED appeared as 'led5' in sysfs
before and as 'red:debug' after this change.

        pwm_leds {
                compatible = "pwm-leds";

                led5 {
                        function = LED_FUNCTION_DEBUG;
                        color = <LED_COLOR_ID_RED>;
                        pwms = <&pwm0 2 10000000 0>;
                        max-brightness = <127>;

                        linux,default-trigger = "heartbeat";
                        panic-indicator;
                };
        };

Signed-off-by: Alexander Dahl <post@lespocky.de>
---

Notes:
    v3 -> v4:
      * simplified implementation based on a new change in led-core
      * removed Acked-by due to changed implementation
    
    v2 -> v3:
      * added Acked-by
    
    v1 -> v2:
      * no change to this patch

 drivers/leds/leds-pwm.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/leds/leds-pwm.c b/drivers/leds/leds-pwm.c
index ef7b91bd2064..9017d3e7dd94 100644
--- a/drivers/leds/leds-pwm.c
+++ b/drivers/leds/leds-pwm.c
@@ -65,6 +65,7 @@ static int led_pwm_add(struct device *dev, struct led_pwm_priv *priv,
 		       struct led_pwm *led, struct fwnode_handle *fwnode)
 {
 	struct led_pwm_data *led_data = &priv->leds[priv->num_leds];
+	struct led_init_data init_data = { .fwnode = fwnode };
 	int ret;
 
 	led_data->active_low = led->active_low;
@@ -90,7 +91,7 @@ static int led_pwm_add(struct device *dev, struct led_pwm_priv *priv,
 
 	pwm_init_state(led_data->pwm, &led_data->pwmstate);
 
-	ret = devm_led_classdev_register(dev, &led_data->cdev);
+	ret = devm_led_classdev_register_ext(dev, &led_data->cdev, &init_data);
 	if (ret) {
 		dev_err(dev, "failed to register PWM led for %s: %d\n",
 			led->name, ret);
-- 
2.20.1