driver core: add root_device_register()

Add support for allocating root device objects which group
device objects under /sys/devices directories.

Also add a sysfs 'module' symlink which points to the owner
of the root device object. This symlink will be used in virtio
to allow userspace to determine which virtio bus implementation
a given device is associated with.

[Includes suggestions from Cornelia Huck]

Signed-off-by: Mark McLoughlin <markmc@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/drivers/base/core.c b/drivers/base/core.c
index ee555d7d5c3f6d73018491f1ad6802b49548bc46..61df508fa62bfef83754e143c4f20cdd6fdbe2e3 100644 (file)
--- a/drivers/base/core.c
+++ b/drivers/base/core.c
@@ -1217,6 +1217,97 @@ EXPORT_SYMBOL_GPL(put_device);
 EXPORT_SYMBOL_GPL(device_create_file);
 EXPORT_SYMBOL_GPL(device_remove_file);
 
+struct root_device
+{
+       struct device dev;
+       struct module *owner;
+};
+
+#define to_root_device(dev) container_of(dev, struct root_device, dev)
+
+static void root_device_release(struct device *dev)
+{
+       kfree(to_root_device(dev));
+}
+
+/**
+ * __root_device_register - allocate and register a root device
+ * @name: root device name
+ * @owner: owner module of the root device, usually THIS_MODULE
+ *
+ * This function allocates a root device and registers it
+ * using device_register(). In order to free the returned
+ * device, use root_device_unregister().
+ *
+ * Root devices are dummy devices which allow other devices
+ * to be grouped under /sys/devices. Use this function to
+ * allocate a root device and then use it as the parent of
+ * any device which should appear under /sys/devices/{name}
+ *
+ * The /sys/devices/{name} directory will also contain a
+ * 'module' symlink which points to the @owner directory
+ * in sysfs.
+ *
+ * Note: You probably want to use root_device_register().
+ */
+struct device *__root_device_register(const char *name, struct module *owner)
+{
+       struct root_device *root;
+       int err = -ENOMEM;
+
+       root = kzalloc(sizeof(struct root_device), GFP_KERNEL);
+       if (!root)
+               return ERR_PTR(err);
+
+       err = dev_set_name(&root->dev, name);
+       if (err) {
+               kfree(root);
+               return ERR_PTR(err);
+       }
+
+       root->dev.release = root_device_release;
+
+       err = device_register(&root->dev);
+       if (err) {
+               put_device(&root->dev);
+               return ERR_PTR(err);
+       }
+
+#ifdef CONFIG_MODULE   /* gotta find a "cleaner" way to do this */
+       if (owner) {
+               struct module_kobject *mk = &owner->mkobj;
+
+               err = sysfs_create_link(&root->dev.kobj, &mk->kobj, "module");
+               if (err) {
+                       device_unregister(&root->dev);
+                       return ERR_PTR(err);
+               }
+               root->owner = owner;
+       }
+#endif
+
+       return &root->dev;
+}
+EXPORT_SYMBOL_GPL(__root_device_register);
+
+/**
+ * root_device_unregister - unregister and free a root device
+ * @root: device going away.
+ *
+ * This function unregisters and cleans up a device that was created by
+ * root_device_register().
+ */
+void root_device_unregister(struct device *dev)
+{
+       struct root_device *root = to_root_device(dev);
+
+       if (root->owner)
+               sysfs_remove_link(&root->dev.kobj, "module");
+
+       device_unregister(dev);
+}
+EXPORT_SYMBOL_GPL(root_device_unregister);
+
 
 static void device_create_release(struct device *dev)
 {

diff --git a/include/linux/device.h b/include/linux/device.h
index b97a0cf1eb0585c88ed4f3db800beda65ef0fc5a..7d9da4b4993feae592388717bff9ffedb0e60531 100644 (file)
--- a/include/linux/device.h
+++ b/include/linux/device.h
@@ -482,6 +482,17 @@ extern struct device *device_find_child(struct device *dev, void *data,
 extern int device_rename(struct device *dev, char *new_name);
 extern int device_move(struct device *dev, struct device *new_parent);
 
+/*
+ * Root device objects for grouping under /sys/devices
+ */
+extern struct device *__root_device_register(const char *name,
+                                            struct module *owner);
+static inline struct device *root_device_register(const char *name)
+{
+       return __root_device_register(name, THIS_MODULE);
+}
+extern void root_device_unregister(struct device *root);
+
 /*
  * Manual binding of a device to driver. See drivers/base/bus.c
  * for information on use.