linux-kernel - [PATCH/RFC v4 06/21] leds: add API for setting torch brightness

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Message-id: <1405087464-13762-7-git-send-email-j.anaszewski@samsung.com>
Date:	Fri, 11 Jul 2014 16:04:09 +0200
From:	Jacek Anaszewski <j.anaszewski@...sung.com>
To:	linux-leds@...r.kernel.org, devicetree@...r.kernel.org,
	linux-media@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:	kyungmin.park@...sung.com, b.zolnierkie@...sung.com,
	Jacek Anaszewski <j.anaszewski@...sung.com>,
	Bryan Wu <cooloney@...il.com>,
	Richard Purdie <rpurdie@...ys.net>
Subject: [PATCH/RFC v4 06/21] leds: add API for setting torch brightness

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
limitiation 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 decices 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@...sung.com>
Acked-by: Kyungmin Park <kyungmin.park@...sung.com>
Cc: Bryan Wu <cooloney@...il.com>
Cc: Richard Purdie <rpurdie@...ys.net>
---
 drivers/leds/led-class.c |   18 ++++++++++++++++--
 drivers/leds/led-core.c  |   15 +++++++++++++++
 include/linux/leds.h     |   22 ++++++++++++++++++++++
 3 files changed, 53 insertions(+), 2 deletions(-)

diff --git a/drivers/leds/led-class.c b/drivers/leds/led-class.c
index a96a1a7..c17dda0 100644
--- a/drivers/leds/led-class.c
+++ b/drivers/leds/led-class.c
@@ -44,15 +44,29 @@ static ssize_t brightness_store(struct device *dev,
 
 	mutex_lock(&led_cdev->led_lock);
 
+	/*
+	 * Having LED_DEV_CAP_TORCH implies this is LED Flash Class
+	 * device and we need to check sysfs accessibility.
+	 */
+	if (led_cdev->flags & LED_DEV_CAP_TORCH) {
+		if (led_sysfs_is_locked(led_cdev)) {
+			ret = -EBUSY;
+			goto unlock;
+		}
+	}
+
 	ret = kstrtoul(buf, 10, &state);
 	if (ret)
 		goto unlock;
 
 	if (state == LED_OFF)
 		led_trigger_remove(led_cdev);
-	__led_set_brightness(led_cdev, state);
 
-	return size;
+	if (led_cdev->flags & LED_DEV_CAP_TORCH)
+		ret = led_set_torch_brightness(led_cdev, state);
+	else
+		__led_set_brightness(led_cdev, state);
+
 	ret = size;
 unlock:
 	mutex_unlock(&led_cdev->led_lock);
diff --git a/drivers/leds/led-core.c b/drivers/leds/led-core.c
index d156fb6..0ce087a 100644
--- a/drivers/leds/led-core.c
+++ b/drivers/leds/led-core.c
@@ -143,6 +143,21 @@ int led_update_brightness(struct led_classdev *led_cdev)
 	return ret;
 }
 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_lock held */
 void led_sysfs_lock(struct led_classdev *led_cdev)
 {
diff --git a/include/linux/leds.h b/include/linux/leds.h
index 1a130cc..9bea9e6 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_LOCK		(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);
 
@@ -156,6 +166,18 @@ 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_lock - lock LED sysfs interface
  * @led_cdev: the LED to set
  *
-- 
1.7.9.5

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