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authorJacek Anaszewski <j.anaszewski@samsung.com>2014-09-22 08:21:04 -0700
committerBryan Wu <cooloney@gmail.com>2014-11-14 14:29:35 -0800
commitacd899e4f3066b6662f6047da5b795cc762093cb (patch)
tree8a0cdf6849c1aec46d741ddee463067951a942ed /drivers/leds/led-triggers.c
parent3f6e42c808409c40dd0d0f8fe2022d197b27455e (diff)
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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: 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-triggers.c')
-rw-r--r--drivers/leds/led-triggers.c16
1 files changed, 13 insertions, 3 deletions
diff --git a/drivers/leds/led-triggers.c b/drivers/leds/led-triggers.c
index c3734f10fdd5..e8b1120f486d 100644
--- a/drivers/leds/led-triggers.c
+++ b/drivers/leds/led-triggers.c
@@ -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);