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leds: Fix race between LED device uevent and actual attributes creation 

If we were to dynamically register/unregister leds and have udev or other
daemons handle the leds class uevents, we would be notified of the adding of a
new LED and if the daemon immediately tries to open one of the attributes of
the led device, it would fail with a "no such file or directory" error since
this the attributes are not yet created. Fix this by switching attributes to be
class-wide, such that the driver core will register these attributes with
device_add_attrs and then emit the kobject_uevent ADD signal.

Signed-off-by:  Fainelli <ffainelli@freebox.fr>
Signed-off-by: Richard Purdie <rpurdie@linux.intel.com>
This commit is contained in:
Florian Fainelli 2010-03-10 18:32:18 +01:00 committed by Richard Purdie
parent 0493a4ff10
commit 14b5d6dd40
1 changed files with 8 additions and 32 deletions
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40
drivers/leds/led-class.c
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@ -72,11 +72,14 @@ static ssize_t led_max_brightness_show(struct device *dev,
return sprintf(buf, "%u\n", led_cdev->max_brightness);
}
static DEVICE_ATTR(brightness, 0644, led_brightness_show, led_brightness_store);
static DEVICE_ATTR(max_brightness, 0444, led_max_brightness_show, NULL);
static struct device_attribute led_class_attrs[] = {
__ATTR(brightness, 0644, led_brightness_show, led_brightness_store),
__ATTR(max_brightness, 0644, led_max_brightness_show, NULL),
#ifdef CONFIG_LEDS_TRIGGERS
static DEVICE_ATTR(trigger, 0644, led_trigger_show, led_trigger_store);
__ATTR(trigger, 0644, led_trigger_show, led_trigger_store),
#endif
__ATTR_NULL,
};
/**
* led_classdev_suspend - suspend an led_classdev.
@ -127,18 +130,11 @@ static int led_resume(struct device *dev)
*/
int led_classdev_register(struct device *parent, struct led_classdev *led_cdev)
{
int rc;
led_cdev->dev = device_create(leds_class, parent, 0, led_cdev,
"%s", led_cdev->name);
if (IS_ERR(led_cdev->dev))
return PTR_ERR(led_cdev->dev);
/* register the attributes */
rc = device_create_file(led_cdev->dev, &dev_attr_brightness);
if (rc)
goto err_out;
#ifdef CONFIG_LEDS_TRIGGERS
init_rwsem(&led_cdev->trigger_lock);
#endif
@ -150,17 +146,9 @@ int led_classdev_register(struct device *parent, struct led_classdev *led_cdev)
if (!led_cdev->max_brightness)
led_cdev->max_brightness = LED_FULL;
rc = device_create_file(led_cdev->dev, &dev_attr_max_brightness);
if (rc)
goto err_out_attr_max;
led_update_brightness(led_cdev);
#ifdef CONFIG_LEDS_TRIGGERS
rc = device_create_file(led_cdev->dev, &dev_attr_trigger);
if (rc)
goto err_out_led_list;
led_trigger_set_default(led_cdev);
#endif
@ -168,18 +156,8 @@ int led_classdev_register(struct device *parent, struct led_classdev *led_cdev)
led_cdev->name);
return 0;
#ifdef CONFIG_LEDS_TRIGGERS
err_out_led_list:
device_remove_file(led_cdev->dev, &dev_attr_max_brightness);
#endif
err_out_attr_max:
device_remove_file(led_cdev->dev, &dev_attr_brightness);
list_del(&led_cdev->node);
err_out:
device_unregister(led_cdev->dev);
return rc;
}
EXPORT_SYMBOL_GPL(led_classdev_register);
/**
@ -190,10 +168,7 @@ EXPORT_SYMBOL_GPL(led_classdev_register);
*/
void led_classdev_unregister(struct led_classdev *led_cdev)
{
device_remove_file(led_cdev->dev, &dev_attr_max_brightness);
device_remove_file(led_cdev->dev, &dev_attr_brightness);
#ifdef CONFIG_LEDS_TRIGGERS
device_remove_file(led_cdev->dev, &dev_attr_trigger);
down_write(&led_cdev->trigger_lock);
if (led_cdev->trigger)
led_trigger_set(led_cdev, NULL);
@ -215,6 +190,7 @@ static int __init leds_init(void)
return PTR_ERR(leds_class);
leds_class->suspend = led_suspend;
leds_class->resume = led_resume;
leds_class->dev_attrs = led_class_attrs;
return 0;
}