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leds: implement sysfs interface locking mechanism

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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: 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>
This commit is contained in:
Jacek Anaszewski
2014-09-22 08:21:04 -07:00
committed by Bryan Wu
parent 3f6e42c808
commit acd899e4f3
4 changed files with 79 additions and 6 deletions
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include/linux/leds.h
+32
View File
@@ -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
*/