[PATCH/RFC v6 2/3] leds: add API for setting torch brightness

[Jacek Anaszewski <j.anaszewski@samsung.com>]

This patch prepares ground for addition of LED Flash Class extension to
the LED subsystem. Since turning the torch on must have guaranteed
immediate effect the brightness_set op can't be used for it. Drivers must
schedule a work queue task in this op to be compatible with led-triggers,
which call brightess_set from timer irqs. In order to address this
limitation a torch_brightness_set op and led_set_torch_brightness API
is introduced. Setting brightness sysfs attribute will result in calling
brightness_set op for LED Class devices and torch_brightness_set op for
LED Flash Class devices, whereas triggers will still call brightness
op in both cases.

Signed-off-by: Jacek Anaszewski <j.anaszewski@samsung.com>
Acked-by: Kyungmin Park <kyungmin.park@samsung.com>
Cc: Bryan Wu <cooloney@gmail.com>
Cc: Richard Purdie <rpurdie@rpsys.net>
---
 drivers/leds/led-class.c |    9 +++++++--
 drivers/leds/led-core.c  |   14 ++++++++++++++
 include/linux/leds.h     |   21 +++++++++++++++++++++
 3 files changed, 42 insertions(+), 2 deletions(-)

diff --git a/drivers/leds/led-class.c b/drivers/leds/led-class.c
index a39ca8f..5a11a07 100644
--- a/drivers/leds/led-class.c
+++ b/drivers/leds/led-class.c
@@ -54,9 +54,14 @@ static ssize_t brightness_store(struct device *dev,
 
 	if (state == LED_OFF)
 		led_trigger_remove(led_cdev);
-	__led_set_brightness(led_cdev, state);
 
-	ret = size;
+	if (led_cdev->flags & LED_DEV_CAP_TORCH)
+		ret = led_set_torch_brightness(led_cdev, state);
+	else
+		__led_set_brightness(led_cdev, state);
+
+	if (!ret)
+		ret = size;
 unlock:
 	mutex_unlock(&led_cdev->led_access);
 	return ret;
diff --git a/drivers/leds/led-core.c b/drivers/leds/led-core.c
index cca86ab..c6d8288 100644
--- a/drivers/leds/led-core.c
+++ b/drivers/leds/led-core.c
@@ -143,6 +143,20 @@ int led_update_brightness(struct led_classdev *led_cdev)
 }
 EXPORT_SYMBOL(led_update_brightness);
 
+int led_set_torch_brightness(struct led_classdev *led_cdev,
+				enum led_brightness brightness)
+{
+	int ret = 0;
+
+	led_cdev->brightness = min(brightness, led_cdev->max_brightness);
+
+	if (!(led_cdev->flags & LED_SUSPENDED))
+		ret = led_cdev->torch_brightness_set(led_cdev,
+						     led_cdev->brightness);
+	return ret;
+}
+EXPORT_SYMBOL_GPL(led_set_torch_brightness);
+
 /* Caller must ensure led_cdev->led_access held */
 void led_sysfs_disable(struct led_classdev *led_cdev)
 {
diff --git a/include/linux/leds.h b/include/linux/leds.h
index 44c8a98..bc2a570 100644
--- a/include/linux/leds.h
+++ b/include/linux/leds.h
@@ -44,11 +44,21 @@ struct led_classdev {
 #define LED_BLINK_ONESHOT_STOP	(1 << 18)
 #define LED_BLINK_INVERT	(1 << 19)
 #define LED_SYSFS_DISABLE	(1 << 20)
+#define LED_DEV_CAP_TORCH	(1 << 21)
 
 	/* 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 immediately - it is required for flash led
+	 * devices as they require setting torch brightness to have immediate
+	 * effect. brightness_set op cannot be used for this purpose because
+	 * the led drivers schedule a work queue task in it to allow for
+	 * being called from led-triggers, i.e. from the timer irq context.
+	 */
+	int		(*torch_brightness_set)(struct led_classdev *led_cdev,
+					enum led_brightness brightness);
 	/* Get LED brightness level */
 	enum led_brightness (*brightness_get)(struct led_classdev *led_cdev);
 
@@ -157,6 +167,17 @@ extern void led_set_brightness(struct led_classdev *led_cdev,
 extern int led_update_brightness(struct led_classdev *led_cdev);
 
 /**
+ * led_set_torch_brightness - set torch LED brightness
+ * @led_cdev: the LED to set
+ * @brightness: the brightness to set it to
+ *
+ * Returns: 0 on success or negative error value on failure
+ *
+ * Set a torch LED's brightness.
+ */
+extern int led_set_torch_brightness(struct led_classdev *led_cdev,
+					enum led_brightness brightness);
+/**
  * led_sysfs_disable - disable LED sysfs interface
  * @led_cdev: the LED to set
  *
-- 
1.7.9.5