driver core: Introduce device_create_groups

device_create_groups lets callers create devices as well as associated
sysfs attributes with a single call. This avoids race conditions seen
if sysfs attributes on new devices are created later.

[fixed up comment block placement and add checks for printk buffer
formats - gregkh]

Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Cc: Jean Delvare <khali@linux-fr.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/base/core.c

@@ -1667,6 +1667,46 @@ static void device_create_release(struct device *dev)
 	kfree(dev);
 }
 
+static struct device *
+device_create_groups_vargs(struct class *class, struct device *parent,
+			   dev_t devt, void *drvdata,
+			   const struct attribute_group **groups,
+			   const char *fmt, va_list args)
+{
+	struct device *dev = NULL;
+	int retval = -ENODEV;
+
+	if (class == NULL || IS_ERR(class))
+		goto error;
+
+	dev = kzalloc(sizeof(*dev), GFP_KERNEL);
+	if (!dev) {
+		retval = -ENOMEM;
+		goto error;
+	}
+
+	dev->devt = devt;
+	dev->class = class;
+	dev->parent = parent;
+	dev->groups = groups;
+	dev->release = device_create_release;
+	dev_set_drvdata(dev, drvdata);
+
+	retval = kobject_set_name_vargs(&dev->kobj, fmt, args);
+	if (retval)
+		goto error;
+
+	retval = device_register(dev);
+	if (retval)
+		goto error;
+
+	return dev;
+
+error:
+	put_device(dev);
+	return ERR_PTR(retval);
+}
+
 /**
  * device_create_vargs - creates a device and registers it with sysfs
  * @class: pointer to the struct class that this device should be registered to
@@ -1696,37 +1736,8 @@ struct device *device_create_vargs(struct class *class, struct device *parent,
 				   dev_t devt, void *drvdata, const char *fmt,
 				   va_list args)
 {
-	struct device *dev = NULL;
+	return device_create_groups_vargs(class, parent, devt, drvdata, NULL,
-	int retval = -ENODEV;
+					  fmt, args);
-
-	if (class == NULL || IS_ERR(class))
-		goto error;
-
-	dev = kzalloc(sizeof(*dev), GFP_KERNEL);
-	if (!dev) {
-		retval = -ENOMEM;
-		goto error;
-	}
-
-	dev->devt = devt;
-	dev->class = class;
-	dev->parent = parent;
-	dev->release = device_create_release;
-	dev_set_drvdata(dev, drvdata);
-
-	retval = kobject_set_name_vargs(&dev->kobj, fmt, args);
-	if (retval)
-		goto error;
-
-	retval = device_register(dev);
-	if (retval)
-		goto error;
-
-	return dev;
-
-error:
-	put_device(dev);
-	return ERR_PTR(retval);
 }
 EXPORT_SYMBOL_GPL(device_create_vargs);
 
@@ -1767,6 +1778,50 @@ struct device *device_create(struct class *class, struct device *parent,
 }
 EXPORT_SYMBOL_GPL(device_create);
 
+/**
+ * device_create_with_groups - creates a device and registers it with sysfs
+ * @class: pointer to the struct class that this device should be registered to
+ * @parent: pointer to the parent struct device of this new device, if any
+ * @devt: the dev_t for the char device to be added
+ * @drvdata: the data to be added to the device for callbacks
+ * @groups: NULL-terminated list of attribute groups to be created
+ * @fmt: string for the device's name
+ *
+ * This function can be used by char device classes.  A struct device
+ * will be created in sysfs, registered to the specified class.
+ * Additional attributes specified in the groups parameter will also
+ * be created automatically.
+ *
+ * A "dev" file will be created, showing the dev_t for the device, if
+ * the dev_t is not 0,0.
+ * If a pointer to a parent struct device is passed in, the newly created
+ * struct device will be a child of that device in sysfs.
+ * The pointer to the struct device will be returned from the call.
+ * Any further sysfs files that might be required can be created using this
+ * pointer.
+ *
+ * Returns &struct device pointer on success, or ERR_PTR() on error.
+ *
+ * Note: the struct class passed to this function must have previously
+ * been created with a call to class_create().
+ */
+struct device *device_create_with_groups(struct class *class,
+					 struct device *parent, dev_t devt,
+					 void *drvdata,
+					 const struct attribute_group **groups,
+					 const char *fmt, ...)
+{
+	va_list vargs;
+	struct device *dev;
+
+	va_start(vargs, fmt);
+	dev = device_create_groups_vargs(class, parent, devt, drvdata, groups,
+					 fmt, vargs);
+	va_end(vargs);
+	return dev;
+}
+EXPORT_SYMBOL_GPL(device_create_with_groups);
+
 static int __match_devt(struct device *dev, const void *data)
 {
 	const dev_t *devt = data;

include/linux/device.h

@@ -938,6 +938,11 @@ extern __printf(5, 6)
 struct device *device_create(struct class *cls, struct device *parent,
 			     dev_t devt, void *drvdata,
 			     const char *fmt, ...);
+extern __printf(6, 7)
+struct device *device_create_with_groups(struct class *cls,
+			     struct device *parent, dev_t devt, void *drvdata,
+			     const struct attribute_group **groups,
+			     const char *fmt, ...);
 extern void device_destroy(struct class *cls, dev_t devt);
 
 /*