leds-lp55xx: support device specific attributes

 To support device specific attributes, new common driver function is added.
 Eventually those are created on registering the sysfs with common dev attrs.
 Furthermore, this patch makes adding device attributes simple in each driver.

Signed-off-by: Milo(Woogyom) Kim <milo.kim@ti.com>
Signed-off-by: Bryan Wu <cooloney@gmail.com>
diff --git a/drivers/leds/leds-lp55xx-common.c b/drivers/leds/leds-lp55xx-common.c
index 578902a..9638ad4 100644
--- a/drivers/leds/leds-lp55xx-common.c
+++ b/drivers/leds/leds-lp55xx-common.c
@@ -493,8 +493,19 @@
 int lp55xx_register_sysfs(struct lp55xx_chip *chip)
 {
 	struct device *dev = &chip->cl->dev;
+	struct lp55xx_device_config *cfg = chip->cfg;
+	int ret;
 
-	return sysfs_create_group(&dev->kobj, &lp55xx_engine_attr_group);
+	if (!cfg->run_engine || !cfg->firmware_cb)
+		goto dev_specific_attrs;
+
+	ret = sysfs_create_group(&dev->kobj, &lp55xx_engine_attr_group);
+	if (ret)
+		return ret;
+
+dev_specific_attrs:
+	return cfg->dev_attr_group ?
+		sysfs_create_group(&dev->kobj, cfg->dev_attr_group) : 0;
 }
 EXPORT_SYMBOL_GPL(lp55xx_register_sysfs);