leds: Add support for setting brightness in a synchronous way

There are use cases when setting a LED brightness has to
have immediate effect (e.g. setting a torch LED brightness).
This patch extends LED subsystem to support such operations.
The LED subsystem internal API __led_set_brightness is changed
to led_set_brightness_async and new led_set_brightness_sync API
is added.

Signed-off-by: Jacek Anaszewski <j.anaszewski@samsung.com>
Acked-by: Kyungmin Park <kyungmin.park@samsung.com>
Cc: Richard Purdie <rpurdie@rpsys.net>
Signed-off-by: Bryan Wu <cooloney@gmail.com>

drivers/leds/led-class.c

@@ -55,7 +55,7 @@ static ssize_t brightness_store(struct device *dev,
 
 	if (state == LED_OFF)
 		led_trigger_remove(led_cdev);
-	__led_set_brightness(led_cdev, state);
+	led_set_brightness(led_cdev, state);
 
 	ret = size;
 unlock:
@@ -109,7 +109,7 @@ static void led_timer_function(unsigned long data)
 	unsigned long delay;
 
 	if (!led_cdev->blink_delay_on || !led_cdev->blink_delay_off) {
-		__led_set_brightness(led_cdev, LED_OFF);
+		led_set_brightness_async(led_cdev, LED_OFF);
 		return;
 	}
 
@@ -132,7 +132,7 @@ static void led_timer_function(unsigned long data)
 		delay = led_cdev->blink_delay_off;
 	}
 
-	__led_set_brightness(led_cdev, brightness);
+	led_set_brightness_async(led_cdev, brightness);
 
 	/* Return in next iteration if led is in one-shot mode and we are in
 	 * the final blink state so that the led is toggled each delay_on +
@@ -158,7 +158,7 @@ static void set_brightness_delayed(struct work_struct *ws)
 
 	led_stop_software_blink(led_cdev);
 
-	__led_set_brightness(led_cdev, led_cdev->delayed_set_value);
+	led_set_brightness_async(led_cdev, led_cdev->delayed_set_value);
 }
 
 /**
@@ -233,6 +233,8 @@ int led_classdev_register(struct device *parent, struct led_classdev *led_cdev)
 	if (!led_cdev->max_brightness)
 		led_cdev->max_brightness = LED_FULL;
 
+	led_cdev->flags |= SET_BRIGHTNESS_ASYNC;
+
 	led_update_brightness(led_cdev);
 
 	INIT_WORK(&led_cdev->set_brightness_work, set_brightness_delayed);

drivers/leds/led-core.c

@@ -42,13 +42,13 @@ static void led_set_software_blink(struct led_classdev *led_cdev,
 
 	/* never on - just set to off */
 	if (!delay_on) {
-		__led_set_brightness(led_cdev, LED_OFF);
+		led_set_brightness_async(led_cdev, LED_OFF);
 		return;
 	}
 
 	/* never off - just set to brightness */
 	if (!delay_off) {
-		__led_set_brightness(led_cdev, led_cdev->blink_brightness);
+		led_set_brightness_async(led_cdev, led_cdev->blink_brightness);
 		return;
 	}
 
@@ -117,6 +117,8 @@ EXPORT_SYMBOL_GPL(led_stop_software_blink);
 void led_set_brightness(struct led_classdev *led_cdev,
 			enum led_brightness brightness)
 {
+	int ret = 0;
+
 	/* delay brightness setting if need to stop soft-blink timer */
 	if (led_cdev->blink_delay_on || led_cdev->blink_delay_off) {
 		led_cdev->delayed_set_value = brightness;
@@ -124,7 +126,17 @@ void led_set_brightness(struct led_classdev *led_cdev,
 		return;
 	}
 
-	__led_set_brightness(led_cdev, brightness);
+	if (led_cdev->flags & SET_BRIGHTNESS_ASYNC) {
+		led_set_brightness_async(led_cdev, brightness);
+		return;
+	} else if (led_cdev->flags & SET_BRIGHTNESS_SYNC)
+		ret = led_set_brightness_sync(led_cdev, brightness);
+	else
+		ret = -EINVAL;
+
+	if (ret < 0)
+		dev_dbg(led_cdev->dev, "Setting LED brightness failed (%d)\n",
+			ret);
 }
 EXPORT_SYMBOL(led_set_brightness);
 

drivers/leds/leds.h

@@ -17,16 +17,28 @@
 #include <linux/rwsem.h>
 #include <linux/leds.h>
 
-static inline void __led_set_brightness(struct led_classdev *led_cdev,
+static inline void led_set_brightness_async(struct led_classdev *led_cdev,
 					enum led_brightness value)
 {
-	if (value > led_cdev->max_brightness)
-		value = led_cdev->max_brightness;
-	led_cdev->brightness = value;
+	led_cdev->brightness = min(value, led_cdev->max_brightness);
+
 	if (!(led_cdev->flags & LED_SUSPENDED))
 		led_cdev->brightness_set(led_cdev, value);
 }
 
+static inline int led_set_brightness_sync(struct led_classdev *led_cdev,
+					enum led_brightness value)
+{
+	int ret = 0;
+
+	led_cdev->brightness = min(value, led_cdev->max_brightness);
+
+	if (!(led_cdev->flags & LED_SUSPENDED))
+		ret = led_cdev->brightness_set_sync(led_cdev,
+						led_cdev->brightness);
+	return ret;
+}
+
 static inline int led_get_brightness(struct led_classdev *led_cdev)
 {
 	return led_cdev->brightness;

drivers/leds/trigger/ledtrig-backlight.c

@@ -51,9 +51,9 @@ static int fb_notifier_callback(struct notifier_block *p,
 
 	if ((n->old_status == UNBLANK) ^ n->invert) {
 		n->brightness = led->brightness;
-		__led_set_brightness(led, LED_OFF);
+		led_set_brightness_async(led, LED_OFF);
 	} else {
-		__led_set_brightness(led, n->brightness);
+		led_set_brightness_async(led, n->brightness);
 	}
 
 	n->old_status = new_status;
@@ -89,9 +89,9 @@ static ssize_t bl_trig_invert_store(struct device *dev,
 
 	/* After inverting, we need to update the LED. */
 	if ((n->old_status == BLANK) ^ n->invert)
-		__led_set_brightness(led, LED_OFF);
+		led_set_brightness_async(led, LED_OFF);
 	else
-		__led_set_brightness(led, n->brightness);
+		led_set_brightness_async(led, n->brightness);
 
 	return num;
 }

drivers/leds/trigger/ledtrig-default-on.c

@@ -19,7 +19,7 @@
 
 static void defon_trig_activate(struct led_classdev *led_cdev)
 {
-	__led_set_brightness(led_cdev, led_cdev->max_brightness);
+	led_set_brightness_async(led_cdev, led_cdev->max_brightness);
 }
 
 static struct led_trigger defon_led_trigger = {

drivers/leds/trigger/ledtrig-gpio.c

@@ -54,12 +54,12 @@ static void gpio_trig_work(struct work_struct *work)
 
 	if (tmp) {
 		if (gpio_data->desired_brightness)
-			__led_set_brightness(gpio_data->led,
+			led_set_brightness_async(gpio_data->led,
 					   gpio_data->desired_brightness);
 		else
-			__led_set_brightness(gpio_data->led, LED_FULL);
+			led_set_brightness_async(gpio_data->led, LED_FULL);
 	} else {
-		__led_set_brightness(gpio_data->led, LED_OFF);
+		led_set_brightness_async(gpio_data->led, LED_OFF);
 	}
 }
 

drivers/leds/trigger/ledtrig-heartbeat.c

@@ -74,7 +74,7 @@ static void led_heartbeat_function(unsigned long data)
 		break;
 	}
 
-	__led_set_brightness(led_cdev, brightness);
+	led_set_brightness_async(led_cdev, brightness);
 	mod_timer(&heartbeat_data->timer, jiffies + delay);
 }
 

drivers/leds/trigger/ledtrig-oneshot.c

@@ -63,9 +63,9 @@ static ssize_t led_invert_store(struct device *dev,
 	oneshot_data->invert = !!state;
 
 	if (oneshot_data->invert)
-		__led_set_brightness(led_cdev, LED_FULL);
+		led_set_brightness_async(led_cdev, LED_FULL);
 	else
-		__led_set_brightness(led_cdev, LED_OFF);
+		led_set_brightness_async(led_cdev, LED_OFF);
 
 	return size;
 }

drivers/leds/trigger/ledtrig-transient.c

@@ -41,7 +41,7 @@ static void transient_timer_function(unsigned long data)
 	struct transient_trig_data *transient_data = led_cdev->trigger_data;
 
 	transient_data->activate = 0;
-	__led_set_brightness(led_cdev, transient_data->restore_state);
+	led_set_brightness_async(led_cdev, transient_data->restore_state);
 }
 
 static ssize_t transient_activate_show(struct device *dev,
@@ -72,7 +72,8 @@ static ssize_t transient_activate_store(struct device *dev,
 	if (state == 0 && transient_data->activate == 1) {
 		del_timer(&transient_data->timer);
 		transient_data->activate = state;
-		__led_set_brightness(led_cdev, transient_data->restore_state);
+		led_set_brightness_async(led_cdev,
+					transient_data->restore_state);
 		return size;
 	}
 
@@ -80,7 +81,7 @@ static ssize_t transient_activate_store(struct device *dev,
 	if (state == 1 && transient_data->activate == 0 &&
 	    transient_data->duration != 0) {
 		transient_data->activate = state;
-		__led_set_brightness(led_cdev, transient_data->state);
+		led_set_brightness_async(led_cdev, transient_data->state);
 		transient_data->restore_state =
 		    (transient_data->state == LED_FULL) ? LED_OFF : LED_FULL;
 		mod_timer(&transient_data->timer,
@@ -203,7 +204,8 @@ static void transient_trig_deactivate(struct led_classdev *led_cdev)
 
 	if (led_cdev->activated) {
 		del_timer_sync(&transient_data->timer);
-		__led_set_brightness(led_cdev, transient_data->restore_state);
+		led_set_brightness_async(led_cdev,
+					transient_data->restore_state);
 		device_remove_file(led_cdev->dev, &dev_attr_activate);
 		device_remove_file(led_cdev->dev, &dev_attr_duration);
 		device_remove_file(led_cdev->dev, &dev_attr_state);

include/linux/leds.h

@@ -44,11 +44,19 @@ struct led_classdev {
 #define LED_BLINK_ONESHOT_STOP	(1 << 18)
 #define LED_BLINK_INVERT	(1 << 19)
 #define LED_SYSFS_DISABLE	(1 << 20)
+#define SET_BRIGHTNESS_ASYNC	(1 << 21)
+#define SET_BRIGHTNESS_SYNC	(1 << 22)
 
 	/* Set LED brightness level */
 	/* Must not sleep, use a workqueue if needed */
 	void		(*brightness_set)(struct led_classdev *led_cdev,
 					  enum led_brightness brightness);
+	/*
+	 * Set LED brightness level immediately - it can block the caller for
+	 * the time required for accessing a LED device register.
+	 */
+	int		(*brightness_set_sync)(struct led_classdev *led_cdev,
+					enum led_brightness brightness);
 	/* Get LED brightness level */
 	enum led_brightness (*brightness_get)(struct led_classdev *led_cdev);