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authorJacek Anaszewski <j.anaszewski@samsung.com>2014-09-22 19:21:04 +0400
committerBryan Wu <cooloney@gmail.com>2014-11-15 01:29:35 +0300
commitacd899e4f3066b6662f6047da5b795cc762093cb (patch)
tree8a0cdf6849c1aec46d741ddee463067951a942ed /drivers/leds/led-class.c
parent3f6e42c808409c40dd0d0f8fe2022d197b27455e (diff)
downloadlinux-acd899e4f3066b6662f6047da5b795cc762093cb.tar.xz
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: 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>
Diffstat (limited to 'drivers/leds/led-class.c')
-rw-r--r--drivers/leds/led-class.c19
1 files changed, 16 insertions, 3 deletions
diff --git a/drivers/leds/led-class.c b/drivers/leds/led-class.c
index 7440c58b8e6f..65722deb8d28 100644
--- a/drivers/leds/led-class.c
+++ b/drivers/leds/led-class.c
@@ -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);