Driver core: create devices/virtual/ tree

This change creates a devices/virtual/CLASS_NAME tree for struct devices
that belong to a class, yet do not have a "real" struct device for a
parent.  It automatically creates the directories on the fly as needed.


Cc: Kay Sievers <kay.sievers@vrfy.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

3 files changed, 28 insertions, 1 deletions

diff --git a/drivers/base/class.c b/drivers/base/class.c
index e078bc21d52e..cbdf47c0c60d 100644
--- a/drivers/base/class.c
+++ b/drivers/base/class.c
@@ -19,6 +19,8 @@
 #include <linux/slab.h>
 #include "base.h"
 
+extern struct subsystem devices_subsys;
+
 #define to_class_attr(_attr) container_of(_attr, struct class_attribute, attr)
 #define to_class(obj) container_of(obj, struct class, subsys.kset.kobj)
 
@@ -878,7 +880,22 @@ void class_interface_unregister(struct class_interface *class_intf)
         class_put(parent);
 }
 
+int virtual_device_parent(struct device *dev)
+{
+        if (!dev->class)
+                return -ENODEV;
+
+        if (!dev->class->virtual_dir) {
+                static struct kobject *virtual_dir = NULL;
 
+                if (!virtual_dir)
+                        virtual_dir = kobject_add_dir(&devices_subsys.kset.kobj, "virtual");
+                dev->class->virtual_dir = kobject_add_dir(virtual_dir, dev->class->name);
+        }
+
+        dev->kobj.parent = dev->class->virtual_dir;
+        return 0;
+}
 
 int __init classes_init(void)
 {
diff --git a/drivers/base/core.c b/drivers/base/core.c
index 0db47561331e..e21a65fc043e 100644
--- a/drivers/base/core.c
+++ b/drivers/base/core.c
@@ -378,6 +378,13 @@ int device_add(struct device *dev)
         if (!dev || !strlen(dev->bus_id))
                 goto Error;
 
+        /* if this is a class device, and has no parent, create one */
+        if ((dev->class) && (dev->parent == NULL)) {
+                error = virtual_device_parent(dev);
+                if (error)
+                        goto Error;
+        }
+
         parent = get_device(dev->parent);
 
         pr_debug("DEV: registering device: ID = '%s'\n", dev->bus_id);
diff --git a/include/linux/device.h b/include/linux/device.h
index 3400e09bf458..bbb0d6b5d232 100644
--- a/include/linux/device.h
+++ b/include/linux/device.h
@@ -149,6 +149,8 @@ struct class {
         struct list_head        interfaces;
         struct semaphore        sem;    /* locks both the children and interfaces lists */
 
+        struct kobject          *virtual_dir;
+
         struct class_attribute          * class_attrs;
         struct class_device_attribute   * class_dev_attrs;
         struct device_attribute         * dev_attrs;
@@ -291,7 +293,6 @@ extern struct class_device *class_device_create(struct class *cls,
                                         __attribute__((format(printf,5,6)));
 extern void class_device_destroy(struct class *cls, dev_t devt);
 
-
 /* interface for exporting device attributes */
 struct device_attribute {
         struct attribute        attr;
@@ -400,6 +401,8 @@ extern struct device *device_create(struct class *cls, struct device *parent,
                                     __attribute__((format(printf,4,5)));
 extern void device_destroy(struct class *cls, dev_t devt);
 
+extern int virtual_device_parent(struct device *dev);
+
 /*
  * Platform "fixup" functions - allow the platform to have their say
  * about devices and actions that the general device layer doesn't