From acd899e4f3066b6662f6047da5b795cc762093cb Mon Sep 17 00:00:00 2001 From: Jacek Anaszewski Date: Mon, 22 Sep 2014 08:21:04 -0700 Subject: 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 Acked-by: Kyungmin Park Cc: Richard Purdie Signed-off-by: Bryan Wu --- drivers/leds/led-class.c | 19 ++++++++++++++++--- drivers/leds/led-core.c | 18 ++++++++++++++++++ drivers/leds/led-triggers.c | 16 +++++++++++++--- 3 files changed, 47 insertions(+), 6 deletions(-) (limited to 'drivers/leds') diff --git a/drivers/leds/led-class.c b/drivers/leds/led-class.c index 7440c58..65722de 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); diff --git a/drivers/leds/led-core.c b/drivers/leds/led-core.c index aaa8eba..be6d9fa 100644 --- a/drivers/leds/led-core.c +++ b/drivers/leds/led-core.c @@ -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); diff --git a/drivers/leds/led-triggers.c b/drivers/leds/led-triggers.c index c3734f1..e8b1120 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); -- cgit v1.1