1 files changed, 143 insertions, 9 deletions

diff --git a/drivers/base/core.c b/drivers/base/core.c
index 016312437577..dc3ea237f086 100644
--- a/drivers/base/core.c
+++ b/drivers/base/core.c
@@ -193,12 +193,12 @@ ssize_t device_show_bool(struct device *dev, struct device_attribute *attr,
 EXPORT_SYMBOL_GPL(device_show_bool);
 
 /**
- *	device_release - free device structure.
- *	@kobj:	device's kobject.
+ * device_release - free device structure.
+ * @kobj: device's kobject.
  *
- *	This is called once the reference count for the object
- *	reaches 0. We forward the call to the device's release
- *	method, which should handle actually freeing the structure.
+ * This is called once the reference count for the object
+ * reaches 0. We forward the call to the device's release
+ * method, which should handle actually freeing the structure.
  */
 static void device_release(struct kobject *kobj)
 {
@@ -403,6 +403,36 @@ static ssize_t store_uevent(struct device *dev, struct device_attribute *attr,
 static struct device_attribute uevent_attr =
 	__ATTR(uevent, S_IRUGO | S_IWUSR, show_uevent, store_uevent);
 
+static ssize_t show_online(struct device *dev, struct device_attribute *attr,
+			   char *buf)
+{
+	bool val;
+
+	lock_device_hotplug();
+	val = !dev->offline;
+	unlock_device_hotplug();
+	return sprintf(buf, "%u\n", val);
+}
+
+static ssize_t store_online(struct device *dev, struct device_attribute *attr,
+			    const char *buf, size_t count)
+{
+	bool val;
+	int ret;
+
+	ret = strtobool(buf, &val);
+	if (ret < 0)
+		return ret;
+
+	lock_device_hotplug();
+	ret = val ? device_online(dev) : device_offline(dev);
+	unlock_device_hotplug();
+	return ret < 0 ? ret : count;
+}
+
+static struct device_attribute online_attr =
+	__ATTR(online, S_IRUGO | S_IWUSR, show_online, store_online);
+
 static int device_add_attributes(struct device *dev,
 				 struct device_attribute *attrs)
 {
@@ -516,6 +546,12 @@ static int device_add_attrs(struct device *dev)
 	if (error)
 		goto err_remove_type_groups;
 
+	if (device_supports_offline(dev) && !dev->offline_disabled) {
+		error = device_create_file(dev, &online_attr);
+		if (error)
+			goto err_remove_type_groups;
+	}
+
 	return 0;
 
  err_remove_type_groups:
@@ -536,6 +572,7 @@ static void device_remove_attrs(struct device *dev)
 	struct class *class = dev->class;
 	const struct device_type *type = dev->type;
 
+	device_remove_file(dev, &online_attr);
 	device_remove_groups(dev, dev->groups);
 
 	if (type)
@@ -572,9 +609,11 @@ int device_create_file(struct device *dev,
 
 	if (dev) {
 		WARN(((attr->attr.mode & S_IWUGO) && !attr->store),
-				"Write permission without 'store'\n");
+			"Attribute %s: write permission without 'store'\n",
+			attr->attr.name);
 		WARN(((attr->attr.mode & S_IRUGO) && !attr->show),
-				"Read permission without 'show'\n");
+			"Attribute %s: read permission without 'show'\n",
+			attr->attr.name);
 		error = sysfs_create_file(&dev->kobj, &attr->attr);
 	}
 
@@ -1332,8 +1371,8 @@ const char *device_get_devnode(struct device *dev,
 /**
  * device_for_each_child - device child iterator.
  * @parent: parent struct device.
- * @data: data for the callback.
  * @fn: function to be called for each device.
+ * @data: data for the callback.
  *
  * Iterate over @parent's child devices, and call @fn for each,
  * passing it @data.
@@ -1361,8 +1400,8 @@ int device_for_each_child(struct device *parent, void *data,
 /**
  * device_find_child - device iterator for locating a particular device.
  * @parent: parent struct device
- * @data: Data to pass to match function
  * @match: Callback function to check device
+ * @data: Data to pass to match function
  *
  * This is similar to the device_for_each_child() function above, but it
  * returns a reference to a device that is 'found' for later use, as
@@ -1372,6 +1411,8 @@ int device_for_each_child(struct device *parent, void *data,
  * if it does.  If the callback returns non-zero and a reference to the
  * current device can be obtained, this function will return to the caller
  * and not iterate over any more devices.
+ *
+ * NOTE: you will need to drop the reference with put_device() after use.
  */
 struct device *device_find_child(struct device *parent, void *data,
 				 int (*match)(struct device *dev, void *data))
@@ -1431,6 +1472,99 @@ EXPORT_SYMBOL_GPL(put_device);
 EXPORT_SYMBOL_GPL(device_create_file);
 EXPORT_SYMBOL_GPL(device_remove_file);
 
+static DEFINE_MUTEX(device_hotplug_lock);
+
+void lock_device_hotplug(void)
+{
+	mutex_lock(&device_hotplug_lock);
+}
+
+void unlock_device_hotplug(void)
+{
+	mutex_unlock(&device_hotplug_lock);
+}
+
+static int device_check_offline(struct device *dev, void *not_used)
+{
+	int ret;
+
+	ret = device_for_each_child(dev, NULL, device_check_offline);
+	if (ret)
+		return ret;
+
+	return device_supports_offline(dev) && !dev->offline ? -EBUSY : 0;
+}
+
+/**
+ * device_offline - Prepare the device for hot-removal.
+ * @dev: Device to be put offline.
+ *
+ * Execute the device bus type's .offline() callback, if present, to prepare
+ * the device for a subsequent hot-removal.  If that succeeds, the device must
+ * not be used until either it is removed or its bus type's .online() callback
+ * is executed.
+ *
+ * Call under device_hotplug_lock.
+ */
+int device_offline(struct device *dev)
+{
+	int ret;
+
+	if (dev->offline_disabled)
+		return -EPERM;
+
+	ret = device_for_each_child(dev, NULL, device_check_offline);
+	if (ret)
+		return ret;
+
+	device_lock(dev);
+	if (device_supports_offline(dev)) {
+		if (dev->offline) {
+			ret = 1;
+		} else {
+			ret = dev->bus->offline(dev);
+			if (!ret) {
+				kobject_uevent(&dev->kobj, KOBJ_OFFLINE);
+				dev->offline = true;
+			}
+		}
+	}
+	device_unlock(dev);
+
+	return ret;
+}
+
+/**
+ * device_online - Put the device back online after successful device_offline().
+ * @dev: Device to be put back online.
+ *
+ * If device_offline() has been successfully executed for @dev, but the device
+ * has not been removed subsequently, execute its bus type's .online() callback
+ * to indicate that the device can be used again.
+ *
+ * Call under device_hotplug_lock.
+ */
+int device_online(struct device *dev)
+{
+	int ret = 0;
+
+	device_lock(dev);
+	if (device_supports_offline(dev)) {
+		if (dev->offline) {
+			ret = dev->bus->online(dev);
+			if (!ret) {
+				kobject_uevent(&dev->kobj, KOBJ_ONLINE);
+				dev->offline = false;
+			}
+		} else {
+			ret = 1;
+		}
+	}
+	device_unlock(dev);
+
+	return ret;
+}
+
 struct root_device {
 	struct device dev;
 	struct module *owner;