leds: Fix race between LED device uevent and actual attributes creation
Florian Fainelli [Wed, 10 Mar 2010 17:32:18 +0000 (18:32 +0100)]
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>

drivers/leds/led-class.c

index 349e073..69e7d86 100644 (file)
@@ -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;
 }