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Commit acd899e4 authored by Jacek Anaszewski's avatar Jacek Anaszewski Committed by Bryan Wu
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leds: implement sysfs interface locking mechanism 



Add a mechanism for locking LED subsystem sysfs interface.
This patch prepares ground for addition of LED Flash Class
extension, whose API will be integrated with V4L2 Flash API.
Such a fusion enforces introducing a locking scheme, which
will secure consistent access to the LED Flash Class device.

The mechanism being introduced allows for disabling LED
subsystem sysfs interface by calling led_sysfs_disable function
and enabling it by calling led_sysfs_enable. The functions
alter the LED_SYSFS_DISABLE flag state and must be called
under mutex lock. The state of the lock is checked with use
of led_sysfs_is_disabled function. Such a design allows for
providing immediate feedback to the user space on whether
the LED Flash Class device is available or is under V4L2 Flash
sub-device control.

Signed-off-by: default avatarJacek Anaszewski <j.anaszewski@samsung.com>
Acked-by: default avatarKyungmin Park <kyungmin.park@samsung.com>
Cc: Richard Purdie <rpurdie@rpsys.net>
Signed-off-by: default avatarBryan Wu <cooloney@gmail.com>
parent 3f6e42c8

drivers/leds/led-class.c

+16 −3
Original line number Diff line number Diff line
@@ -40,17 +40,27 @@ static ssize_t brightness_store(struct device *dev, 
{

	struct led_classdev *led_cdev = dev_get_drvdata(dev);

	unsigned long state;

	ssize_t ret = -EINVAL;

	ssize_t ret;



	mutex_lock(&led_cdev->led_access);



	if (led_sysfs_is_disabled(led_cdev)) {

		ret = -EBUSY;

		goto unlock;

	}



	ret = kstrtoul(buf, 10, &state);

	if (ret)

		return ret;

		goto unlock;



	if (state == LED_OFF)

		led_trigger_remove(led_cdev);

	__led_set_brightness(led_cdev, state);



	return size;

	ret = size;

unlock:

	mutex_unlock(&led_cdev->led_access);

	return ret;

}

static DEVICE_ATTR_RW(brightness);
@@ -214,6 +224,7 @@ int led_classdev_register(struct device *parent, struct led_classdev *led_cdev) 
#ifdef CONFIG_LEDS_TRIGGERS

	init_rwsem(&led_cdev->trigger_lock);

#endif

	mutex_init(&led_cdev->led_access);

	/* add to the list of leds */

	down_write(&leds_list_lock);

	list_add_tail(&led_cdev->node, &leds_list);
@@ -267,6 +278,8 @@ void led_classdev_unregister(struct led_classdev *led_cdev) 
	down_write(&leds_list_lock);

	list_del(&led_cdev->node);

	up_write(&leds_list_lock);



	mutex_destroy(&led_cdev->led_access);

}

EXPORT_SYMBOL_GPL(led_classdev_unregister);

drivers/leds/led-core.c

+18 −0
Original line number Diff line number Diff line
@@ -143,3 +143,21 @@ int led_update_brightness(struct led_classdev *led_cdev) 
	return ret;

}

EXPORT_SYMBOL(led_update_brightness);



/* Caller must ensure led_cdev->led_access held */

void led_sysfs_disable(struct led_classdev *led_cdev)

{

	lockdep_assert_held(&led_cdev->led_access);



	led_cdev->flags |= LED_SYSFS_DISABLE;

}

EXPORT_SYMBOL_GPL(led_sysfs_disable);



/* Caller must ensure led_cdev->led_access held */

void led_sysfs_enable(struct led_classdev *led_cdev)

{

	lockdep_assert_held(&led_cdev->led_access);



	led_cdev->flags &= ~LED_SYSFS_DISABLE;

}

EXPORT_SYMBOL_GPL(led_sysfs_enable);

drivers/leds/led-triggers.c

+13 −3
Original line number Diff line number Diff line
@@ -37,6 +37,14 @@ ssize_t led_trigger_store(struct device *dev, struct device_attribute *attr, 
	char trigger_name[TRIG_NAME_MAX];

	struct led_trigger *trig;

	size_t len;

	int ret = count;



	mutex_lock(&led_cdev->led_access);



	if (led_sysfs_is_disabled(led_cdev)) {

		ret = -EBUSY;

		goto unlock;

	}



	trigger_name[sizeof(trigger_name) - 1] = '\0';

	strncpy(trigger_name, buf, sizeof(trigger_name) - 1);
@@ -47,7 +55,7 @@ ssize_t led_trigger_store(struct device *dev, struct device_attribute *attr, 


	if (!strcmp(trigger_name, "none")) {

		led_trigger_remove(led_cdev);

		return count;

		goto unlock;

	}



	down_read(&triggers_list_lock);
@@ -58,12 +66,14 @@ ssize_t led_trigger_store(struct device *dev, struct device_attribute *attr, 
			up_write(&led_cdev->trigger_lock);



			up_read(&triggers_list_lock);

			return count;

			goto unlock;

		}

	}

	up_read(&triggers_list_lock);



	return -EINVAL;

unlock:

	mutex_unlock(&led_cdev->led_access);

	return ret;

}

EXPORT_SYMBOL_GPL(led_trigger_store);

include/linux/leds.h

+32 −0
Original line number Diff line number Diff line
@@ -13,6 +13,7 @@ 
#define __LINUX_LEDS_H_INCLUDED



#include <linux/list.h>

#include <linux/mutex.h>

#include <linux/rwsem.h>

#include <linux/spinlock.h>

#include <linux/timer.h>
@@ -42,6 +43,7 @@ struct led_classdev { 
#define LED_BLINK_ONESHOT	(1 << 17)

#define LED_BLINK_ONESHOT_STOP	(1 << 18)

#define LED_BLINK_INVERT	(1 << 19)

#define LED_SYSFS_DISABLE	(1 << 20)



	/* Set LED brightness level */

	/* Must not sleep, use a workqueue if needed */
@@ -85,6 +87,9 @@ struct led_classdev { 
	/* true if activated - deactivate routine uses it to do cleanup */

	bool			activated;

#endif



	/* Ensures consistent access to the LED Flash Class device */

	struct mutex		led_access;

};



extern int led_classdev_register(struct device *parent,
@@ -151,6 +156,33 @@ extern void led_set_brightness(struct led_classdev *led_cdev, 
 */

extern int led_update_brightness(struct led_classdev *led_cdev);



/**

 * led_sysfs_disable - disable LED sysfs interface

 * @led_cdev: the LED to set

 *

 * Disable the led_cdev's sysfs interface.

 */

extern void led_sysfs_disable(struct led_classdev *led_cdev);



/**

 * led_sysfs_enable - enable LED sysfs interface

 * @led_cdev: the LED to set

 *

 * Enable the led_cdev's sysfs interface.

 */

extern void led_sysfs_enable(struct led_classdev *led_cdev);



/**

 * led_sysfs_is_disabled - check if LED sysfs interface is disabled

 * @led_cdev: the LED to query

 *

 * Returns: true if the led_cdev's sysfs interface is disabled.

 */

static inline bool led_sysfs_is_disabled(struct led_classdev *led_cdev)

{

	return led_cdev->flags & LED_SYSFS_DISABLE;

}



/*

 * LED Triggers

 */