[PATCH 1/6] leds: triggers: let struct led_trigger::activate return an error code

[Uwe Kleine-König <u.kleine-koenig@xxxxxxxxxxxxxx>]

Given that activating a trigger can fail, let the callback return an
indication. This prevents to have a trigger active according to the
"trigger" sysfs attribure but not functional.

This is done using a new function callback .new_activate to not break
existing drivers and to allow to convert one after the other to the new
mechanism. Once all users are converted, .activate can be dropped and
.new_activate renamed.

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@xxxxxxxxxxxxxx>
---
 drivers/leds/led-triggers.c | 29 +++++++++++++++++++++++++----
 include/linux/leds.h        | 14 ++++++++++----
 2 files changed, 35 insertions(+), 8 deletions(-)

diff --git a/drivers/leds/led-triggers.c b/drivers/leds/led-triggers.c
index 327c87ff7646..0ab8ff5eb142 100644
--- a/drivers/leds/led-triggers.c
+++ b/drivers/leds/led-triggers.c
@@ -103,15 +103,16 @@ ssize_t led_trigger_show(struct device *dev, struct device_attribute *attr,
 EXPORT_SYMBOL_GPL(led_trigger_show);
 
 /* Caller must ensure led_cdev->trigger_lock held */
-void led_trigger_set(struct led_classdev *led_cdev, struct led_trigger *trig)
+int led_trigger_set(struct led_classdev *led_cdev, struct led_trigger *trig)
 {
 	unsigned long flags;
 	char *event = NULL;
 	char *envp[2];
 	const char *name;
+	int ret;
 
 	if (!led_cdev->trigger && !trig)
-		return;
+		return 0;
 
 	name = trig ? trig->name : "none";
 	event = kasprintf(GFP_KERNEL, "TRIGGER=%s", name);
@@ -134,8 +135,17 @@ void led_trigger_set(struct led_classdev *led_cdev, struct led_trigger *trig)
 		list_add_tail(&led_cdev->trig_list, &trig->led_cdevs);
 		write_unlock_irqrestore(&trig->leddev_list_lock, flags);
 		led_cdev->trigger = trig;
-		if (trig->activate)
-			trig->activate(led_cdev);
+
+		if (trig->new_activate) {
+			ret = trig->new_activate(led_cdev);
+		} else {
+			if (trig->activate)
+				trig->activate(led_cdev);
+			ret = 0;
+		}
+
+		if (ret)
+			goto err_activate;
 	}
 
 	if (event) {
@@ -146,6 +156,17 @@ void led_trigger_set(struct led_classdev *led_cdev, struct led_trigger *trig)
 				"%s: Error sending uevent\n", __func__);
 		kfree(event);
 	}
+
+	return 0;
+
+err_activate:
+	led_cdev->trigger = 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);
+	led_set_brightness(led_cdev, LED_OFF);
+
+	return ret;
 }
 EXPORT_SYMBOL_GPL(led_trigger_set);
 
diff --git a/include/linux/leds.h b/include/linux/leds.h
index c95eaf6acb23..12c0b0137012 100644
--- a/include/linux/leds.h
+++ b/include/linux/leds.h
@@ -253,6 +253,8 @@ static inline bool led_sysfs_is_disabled(struct led_classdev *led_cdev)
 struct led_trigger {
 	/* Trigger Properties */
 	const char	 *name;
+	int		(*new_activate)(struct led_classdev *led_cdev);
+	/* .activate is unused if .new_activate is non-NULL */
 	void		(*activate)(struct led_classdev *led_cdev);
 	void		(*deactivate)(struct led_classdev *led_cdev);
 
@@ -288,8 +290,8 @@ extern void led_trigger_blink_oneshot(struct led_trigger *trigger,
 				      unsigned long *delay_off,
 				      int invert);
 extern void led_trigger_set_default(struct led_classdev *led_cdev);
-extern void led_trigger_set(struct led_classdev *led_cdev,
-			struct led_trigger *trigger);
+extern int led_trigger_set(struct led_classdev *led_cdev,
+			   struct led_trigger *trigger);
 extern void led_trigger_remove(struct led_classdev *led_cdev);
 
 static inline void *led_get_trigger_data(struct led_classdev *led_cdev)
@@ -316,8 +318,12 @@ static inline void led_trigger_blink_oneshot(struct led_trigger *trigger,
 				      unsigned long *delay_off,
 				      int invert) {}
 static inline void led_trigger_set_default(struct led_classdev *led_cdev) {}
-static inline void led_trigger_set(struct led_classdev *led_cdev,
-				struct led_trigger *trigger) {}
+static inline int led_trigger_set(struct led_classdev *led_cdev,
+				  struct led_trigger *trigger)
+{
+	return 0;
+}
+
 static inline void led_trigger_remove(struct led_classdev *led_cdev) {}
 static inline void *led_get_trigger_data(struct led_classdev *led_cdev)
 {
-- 
2.17.0