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_lock function
and enabling it by calling led_sysfs_unlock. The functions
alter the LED_SYSFS_LOCK flag state and must be called
under mutex lock. The state of the lock is checked with use
of led_sysfs_is_locked 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@xxxxxxxxxxx>
Acked-by: Kyungmin Park <kyungmin.park@xxxxxxxxxxx>
Cc: Bryan Wu <cooloney@xxxxxxxxx>
Cc: Richard Purdie <rpurdie@xxxxxxxxx>
---
drivers/leds/led-class.c | 23 ++++++++++++++++++++---
drivers/leds/led-core.c | 18 ++++++++++++++++++
drivers/leds/led-triggers.c | 15 ++++++++++++---
include/linux/leds.h | 32 ++++++++++++++++++++++++++++++++
4 files changed, 82 insertions(+), 6 deletions(-)
diff --git a/drivers/leds/led-class.c b/drivers/leds/led-class.c
index 6f82a76..0bc0ba9 100644
--- a/drivers/leds/led-class.c
+++ b/drivers/leds/led-class.c
@@ -39,17 +39,31 @@ 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;
+
+#ifdef CONFIG_V4L2_FLASH_LED_CLASS
+ mutex_lock(&led_cdev->led_lock);
+
+ if (led_sysfs_is_locked(led_cdev)) {
+ ret = -EBUSY;
+ goto unlock;
+ }
+#endif
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:
+#ifdef CONFIG_V4L2_FLASH_LED_CLASS
+ mutex_unlock(&led_cdev->led_lock);
+#endif
+ return ret;
}
static DEVICE_ATTR_RW(brightness);
@@ -215,6 +229,7 @@ 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_lock);
/* add to the list of leds */
down_write(&leds_list_lock);
list_add_tail(&led_cdev->node, &leds_list);
@@ -266,6 +281,8 @@ 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_lock);
}
EXPORT_SYMBOL_GPL(led_classdev_unregister);
diff --git a/drivers/leds/led-core.c b/drivers/leds/led-core.c
index 466ce5a..4649ea5 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_lock held */
+void led_sysfs_lock(struct led_classdev *led_cdev)
+{
+ lockdep_assert_held(&led_cdev->led_lock);
+
+ led_cdev->flags |= LED_SYSFS_LOCK;
+}
+EXPORT_SYMBOL_GPL(led_sysfs_lock);
+
+/* Caller must ensure led_cdev->led_lock held */
+void led_sysfs_unlock(struct led_classdev *led_cdev)
+{
+ lockdep_assert_held(&led_cdev->led_lock);
+
+ led_cdev->flags &= ~LED_SYSFS_LOCK;
+}
+EXPORT_SYMBOL_GPL(led_sysfs_unlock);
diff --git a/drivers/leds/led-triggers.c b/drivers/leds/led-triggers.c
index c3734f1..d391a5d 100644
--- a/drivers/leds/led-triggers.c
+++ b/drivers/leds/led-triggers.c
@@ -37,6 +37,11 @@ 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;
+
+#ifdef CONFIG_V4L2_FLASH_LED_CLASS
+ mutex_lock(&led_cdev->led_lock);
+#endif
trigger_name[sizeof(trigger_name) - 1] = '\0';
strncpy(trigger_name, buf, sizeof(trigger_name) - 1);
@@ -47,7 +52,7 @@ 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 exit_unlock;
}
down_read(&triggers_list_lock);
@@ -58,12 +63,16 @@ 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 exit_unlock;
}
}
up_read(&triggers_list_lock);
- return -EINVAL;
+exit_unlock:
+#ifdef CONFIG_V4L2_FLASH_LED_CLASS
+ mutex_unlock(&led_cdev->led_lock);
+#endif
+ return ret;
}
EXPORT_SYMBOL_GPL(led_trigger_store);
diff --git a/include/linux/leds.h b/include/linux/leds.h
index cc85b16..ef343f1 100644
--- a/include/linux/leds.h
+++ b/include/linux/leds.h
@@ -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/workqueue.h>
@@ -41,6 +42,7 @@ 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_LOCK (1 << 20)
/* Set LED brightness level */
/* Must not sleep, use a workqueue if needed */
@@ -84,6 +86,9 @@ 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_lock;
};
extern int led_classdev_register(struct device *parent,
@@ -150,6 +155,33 @@ extern void led_set_brightness(struct led_classdev *led_cdev,
*/
extern int led_update_brightness(struct led_classdev *led_cdev);
+/**
+ * led_sysfs_lock - lock LED sysfs interface
+ * @led_cdev: the LED to set
+ *
+ * Lock the LED's sysfs interface
+ */
+extern void led_sysfs_lock(struct led_classdev *led_cdev);
+
+/**
+ * led_sysfs_unlock - unlock LED sysfs interface
+ * @led_cdev: the LED to set
+ *
+ * Unlock the LED's sysfs interface
+ */
+extern void led_sysfs_unlock(struct led_classdev *led_cdev);
+
+/**
+ * led_sysfs_is_locked
+ * @led_cdev: the LED to query
+ *
+ * Returns: true if the sysfs interface of the led is locked
+ */
+static inline bool led_sysfs_is_locked(struct led_classdev *led_cdev)
+{
+ return led_cdev->flags & LED_SYSFS_LOCK;
+}
+
/*
* LED Triggers
*/
--
1.7.9.5
--
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