[PATCH] USB: only make /sys/class/usb show up when there is something in it

Now /sys/class/usb is dynamically created when we have something to put
in it, and removed when all devices go away.

Just trying to cut down on the clutter in sysfs...

Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/drivers/usb/core/file.c b/drivers/usb/core/file.c
index 70898716dd9a9f4ed4560e7a119826880911c980..f65b193cde3d43ab1a68fdd31575b298990f18cc 100644 (file)
--- a/drivers/usb/core/file.c
+++ b/drivers/usb/core/file.c
@@ -61,33 +61,66 @@ static struct file_operations usb_fops = {
        .open =         usb_open,
 };
 
-static struct class *usb_class;
+static struct usb_class {
+       struct kref kref;
+       struct class *class;
+} *usb_class;
 
-int usb_major_init(void)
+static int init_usb_class(void)
 {
-       int error;
+       int result = 0;
 
-       error = register_chrdev(USB_MAJOR, "usb", &usb_fops);
-       if (error) {
-               err("unable to get major %d for usb devices", USB_MAJOR);
-               goto out;
+       if (usb_class != NULL) {
+               kref_get(&usb_class->kref);
+               goto exit;
+       }
+
+       usb_class = kmalloc(sizeof(*usb_class), GFP_KERNEL);
+       if (!usb_class) {
+               result = -ENOMEM;
+               goto exit;
        }
 
-       usb_class = class_create(THIS_MODULE, "usb");
-       if (IS_ERR(usb_class)) {
-               error = PTR_ERR(usb_class);
+       kref_init(&usb_class->kref);
+       usb_class->class = class_create(THIS_MODULE, "usb");
+       if (IS_ERR(usb_class->class)) {
+               result = IS_ERR(usb_class->class);
                err("class_create failed for usb devices");
-               unregister_chrdev(USB_MAJOR, "usb");
-               goto out;
+               kfree(usb_class);
+               usb_class = NULL;
        }
 
-out:
+exit:
+       return result;
+}
+
+static void release_usb_class(struct kref *kref)
+{
+       /* Ok, we cheat as we know we only have one usb_class */
+       class_destroy(usb_class->class);
+       kfree(usb_class);
+       usb_class = NULL;
+}
+
+static void destroy_usb_class(void)
+{
+       if (usb_class)
+               kref_put(&usb_class->kref, release_usb_class);
+}
+
+int usb_major_init(void)
+{
+       int error;
+
+       error = register_chrdev(USB_MAJOR, "usb", &usb_fops);
+       if (error)
+               err("unable to get major %d for usb devices", USB_MAJOR);
+
        return error;
 }
 
 void usb_major_cleanup(void)
 {
-       class_destroy(usb_class);
        unregister_chrdev(USB_MAJOR, "usb");
 }
 
@@ -146,6 +179,10 @@ int usb_register_dev(struct usb_interface *intf,
        }
        spin_unlock (&minor_lock);
 
+       if (retval)
+               goto exit;
+
+       retval = init_usb_class();
        if (retval)
                goto exit;
 
@@ -158,7 +195,7 @@ int usb_register_dev(struct usb_interface *intf,
                ++temp;
        else
                temp = name;
-       intf->usb_dev = device_create(usb_class, &intf->dev,
+       intf->usb_dev = device_create(usb_class->class, &intf->dev,
                                      MKDEV(USB_MAJOR, minor), "%s", temp);
        if (IS_ERR(intf->usb_dev)) {
                spin_lock (&minor_lock);
@@ -205,9 +242,10 @@ void usb_deregister_dev(struct usb_interface *intf,
        spin_unlock (&minor_lock);
 
        snprintf(name, BUS_ID_SIZE, class_driver->name, intf->minor - minor_base);
-       device_destroy(usb_class, MKDEV(USB_MAJOR, intf->minor));
+       device_destroy(usb_class->class, MKDEV(USB_MAJOR, intf->minor));
        intf->usb_dev = NULL;
        intf->minor = -1;
+       destroy_usb_class();
 }
 EXPORT_SYMBOL(usb_deregister_dev);