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>

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>
Florian Fainelli · Richard Purdie
1 parent 0493a4ff10
Showing 1 changed file with 8 additions and 32 deletions Side-by-side Diff
drivers/leds/led-class.c
@@ -72,11 +72,14 @@
 	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 @@
  */
 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 @@
 	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 @@
 			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 @@
  */
 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 @@
 		return PTR_ERR(leds_class);
 	leds_class->suspend = led_suspend;
 	leds_class->resume = led_resume;
+	leds_class->dev_attrs = led_class_attrs;
 	return 0;
 }
...	...	@@ -72,11 +72,14 @@
72	72	return sprintf(buf, "%u\n", led_cdev->max_brightness);
73	73	}
74	74
75		-static DEVICE_ATTR(brightness, 0644, led_brightness_show, led_brightness_store);
76		-static DEVICE_ATTR(max_brightness, 0444, led_max_brightness_show, NULL);
	75	+static struct device_attribute led_class_attrs[] = {
	76	+ __ATTR(brightness, 0644, led_brightness_show, led_brightness_store),
	77	+ __ATTR(max_brightness, 0644, led_max_brightness_show, NULL),
77	78	#ifdef CONFIG_LEDS_TRIGGERS
78		-static DEVICE_ATTR(trigger, 0644, led_trigger_show, led_trigger_store);
	79	+ __ATTR(trigger, 0644, led_trigger_show, led_trigger_store),
79	80	#endif
	81	+ __ATTR_NULL,
	82	+};
80	83
81	84	/**
82	85	* led_classdev_suspend - suspend an led_classdev.
83	86
...	...	@@ -127,18 +130,11 @@
127	130	*/
128	131	int led_classdev_register(struct device parent, struct led_classdev led_cdev)
129	132	{
130		- int rc;
131		-
132	133	led_cdev->dev = device_create(leds_class, parent, 0, led_cdev,
133	134	"%s", led_cdev->name);
134	135	if (IS_ERR(led_cdev->dev))
135	136	return PTR_ERR(led_cdev->dev);
136	137
137		- /* register the attributes */
138		- rc = device_create_file(led_cdev->dev, &dev_attr_brightness);
139		- if (rc)
140		- goto err_out;
141		-
142	138	#ifdef CONFIG_LEDS_TRIGGERS
143	139	init_rwsem(&led_cdev->trigger_lock);
144	140	#endif
145	141
...	...	@@ -150,17 +146,9 @@
150	146	if (!led_cdev->max_brightness)
151	147	led_cdev->max_brightness = LED_FULL;
152	148
153		- rc = device_create_file(led_cdev->dev, &dev_attr_max_brightness);
154		- if (rc)
155		- goto err_out_attr_max;
156		-
157	149	led_update_brightness(led_cdev);
158	150
159	151	#ifdef CONFIG_LEDS_TRIGGERS
160		- rc = device_create_file(led_cdev->dev, &dev_attr_trigger);
161		- if (rc)
162		- goto err_out_led_list;
163		-
164	152	led_trigger_set_default(led_cdev);
165	153	#endif
166	154
167	155
...	...	@@ -168,18 +156,8 @@
168	156	led_cdev->name);
169	157
170	158	return 0;
171		-
172		-#ifdef CONFIG_LEDS_TRIGGERS
173		-err_out_led_list:
174		- device_remove_file(led_cdev->dev, &dev_attr_max_brightness);
175		-#endif
176		-err_out_attr_max:
177		- device_remove_file(led_cdev->dev, &dev_attr_brightness);
178		- list_del(&led_cdev->node);
179		-err_out:
180		- device_unregister(led_cdev->dev);
181		- return rc;
182	159	}
	160	+
183	161	EXPORT_SYMBOL_GPL(led_classdev_register);
184	162
185	163	/**
186	164
...	...	@@ -190,10 +168,7 @@
190	168	*/
191	169	void led_classdev_unregister(struct led_classdev *led_cdev)
192	170	{
193		- device_remove_file(led_cdev->dev, &dev_attr_max_brightness);
194		- device_remove_file(led_cdev->dev, &dev_attr_brightness);
195	171	#ifdef CONFIG_LEDS_TRIGGERS
196		- device_remove_file(led_cdev->dev, &dev_attr_trigger);
197	172	down_write(&led_cdev->trigger_lock);
198	173	if (led_cdev->trigger)
199	174	led_trigger_set(led_cdev, NULL);
...	...	@@ -215,6 +190,7 @@
215	190	return PTR_ERR(leds_class);
216	191	leds_class->suspend = led_suspend;
217	192	leds_class->resume = led_resume;
	193	+ leds_class->dev_attrs = led_class_attrs;
218	194	return 0;
219	195	}
220	196