kernel: 4.19: fix usbport led trigger regression

|In the patch "usb: simplify usbport trigger" together with
|"leds: triggers: add device attribute support" caused an
|regression for the usbport trigger. it will no longer
|enumerate any "ports" (i.e the sysfs directory stays empty)
|if the usb host drivers are fully initialized before the
|usbport trigger was loaded.

<https://marc.info/?l=linux-usb&m=154577101631079>

Signed-off-by: Christian Lamparter <[email protected]>

target/linux/generic/hack-4.19/160-leds-fix-regression-in-usbport-led-trigger.patch

@@ -0,0 +1,84 @@
+From 38a3549ffc0033761063cc5c7b994ab075694db8 Mon Sep 17 00:00:00 2001
+From: Christian Lamparter <[email protected]>
+Date: Tue, 25 Dec 2018 21:11:08 +0100
+Subject: [RFC PATCH] leds: fix regression in usbport led trigger
+
+In the patch "usb: simplify usbport trigger" together with
+"leds: triggers: add device attribute support" caused an
+regression for the usbport trigger. it will no longer
+enumerate any "ports" (i.e the sysfs directory stays empty)
+if the usb host drivers are fully initialized before the
+usbport trigger was loaded.
+
+The reason is that the usbport driver registers the sysfs
+entries in the ports subdirectory during the activate()
+callback. Whereas the patch
+"leds: triggers: add device attribute support" made it so
+that the sysfs "ports" group was only being added after
+the activate() callback succeeded.
+
+This patch moves the device_add_groups() in front of the
+call to the trigger's activate() function in order to
+solve the problem.
+
+Fixes: 6f7b0bad8839 ("usb: simplify usbport trigger")
+Signed-off-by: Christian Lamparter <[email protected]>
+---
+ drivers/leds/led-triggers.c | 19 ++++++++++---------
+ 1 file changed, 10 insertions(+), 9 deletions(-)
+
+diff --git a/drivers/leds/led-triggers.c b/drivers/leds/led-triggers.c
+index 17d73db1456e..08e7c724a9dc 100644
+--- a/drivers/leds/led-triggers.c
++++ b/drivers/leds/led-triggers.c
+@@ -134,6 +134,12 @@ int led_trigger_set(struct led_classdev *led_cdev, struct led_trigger *trig)
+ 		led_set_brightness(led_cdev, LED_OFF);
+ 	}
+ 	if (trig) {
++		ret = device_add_groups(led_cdev->dev, trig->groups);
++		if (ret) {
++			dev_err(led_cdev->dev, "Failed to add trigger attributes\n");
++			goto err_add_groups;
++		}
++
+ 		write_lock_irqsave(&trig->leddev_list_lock, flags);
+ 		list_add_tail(&led_cdev->trig_list, &trig->led_cdevs);
+ 		write_unlock_irqrestore(&trig->leddev_list_lock, flags);
+@@ -146,12 +152,6 @@ int led_trigger_set(struct led_classdev *led_cdev, struct led_trigger *trig)
+ 
+ 		if (ret)
+ 			goto err_activate;
+-
+-		ret = device_add_groups(led_cdev->dev, trig->groups);
+-		if (ret) {
+-			dev_err(led_cdev->dev, "Failed to add trigger attributes\n");
+-			goto err_add_groups;
+-		}
+ 	}
+ 
+ 	if (event) {
+@@ -165,17 +165,18 @@ int led_trigger_set(struct led_classdev *led_cdev, struct led_trigger *trig)
+ 
+ 	return 0;
+ 
+-err_add_groups:
+-
++err_activate:
++	device_remove_groups(led_cdev->dev, trig->groups);
+ 	if (trig->deactivate)
+ 		trig->deactivate(led_cdev);
+-err_activate:
+ 
+ 	led_cdev->trigger = NULL;
+ 	led_cdev->trigger_data = NULL;
+ 	write_lock_irqsave(&led_cdev->trigger->leddev_list_lock, flags);
+ 	list_del(&led_cdev->trig_list);
+ 	write_unlock_irqrestore(&led_cdev->trigger->leddev_list_lock, flags);
++
++err_add_groups:
+ 	led_set_brightness(led_cdev, LED_OFF);
+ 
+ 	return ret;
+-- 
+2.20.1
+