[PATCH] USB: real nodes instead of usbfs

This patch introduces a /sys/class/usb_device/ class
where every connected usb-device will show up:

  tree /sys/class/usb_device/
  /sys/class/usb_device/
  |-- usb1.1
  |   |-- dev
  |   `-- device -> ../../../devices/pci0000:00/0000:00:1d.0/usb1
  |-- usb2.1
  |   |-- dev
  |   `-- device -> ../../../devices/pci0000:00/0000:00:1d.1/usb2
  ...

The presence of the "dev" file lets udev create real device nodes.
  kay@pim:~/src/linux-2.6> tree /dev/bus/usb/
  /dev/bus/usb/
  |-- 1
  |   `-- 1
  |-- 2
  |   `-- 1
  ...

udev rule:
  SUBSYSTEM="usb_device", PROGRAM="/sbin/usb_device %k", NAME="%c"
  (echo $1 | /bin/sed 's/usb\([0-9]*\)\.\([0-9]*\)/bus\/usb\/\1\/\2/')

This makes libusb pick up the real nodes instead of the mounted usbfs:
  export USB_DEVFS_PATH=/dev/bus/usb

Background:
  All this makes it possible to manage usb devices with udev instead of
  the devfs solution. We are currently working on a pam_console/resmgr
  replacement driven by udev and a pam-helper. It applies ACL's to device
  nodes, which is required for modern desktop functionalty like
  "Fast User Switching" or multiple local login support.

New patch with its own major. I've succesfully disabled usbfs and use real
nodes only on my box. With: "export USB_DEVFS_PATH=/dev/bus/usb" libusb picks
up the udev managed nodes instead of reading usbfs files.

This makes udev to provide symlinks for libusb to pick up:
  SUBSYSTEM="usb_device", PROGRAM="/sbin/usbdevice %k", SYMLINK="%c"

/sbin/usbdevice:
  #!/bin/sh
  echo $1 | /bin/sed 's/usbdev\([0-9]*\)\.\([0-9]*\)/bus\/usb\/\1\/\2/'
Signed-off-by: Kay Sievers <kay.sievers@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/usb/core/Makefile

@@ -3,14 +3,14 @@
 #
 
 usbcore-objs	:= usb.o hub.o hcd.o urb.o message.o \
-			config.o file.o buffer.o sysfs.o
+			config.o file.o buffer.o sysfs.o devio.o
 
 ifeq ($(CONFIG_PCI),y)
 	usbcore-objs	+= hcd-pci.o
 endif
 
 ifeq ($(CONFIG_USB_DEVICEFS),y)
-	usbcore-objs	+= devio.o inode.o devices.o
+	usbcore-objs	+= inode.o devices.o
 endif
 
 obj-$(CONFIG_USB)	+= usbcore.o

drivers/usb/core/devio.c

@@ -43,6 +43,7 @@
 #include <linux/module.h>
 #include <linux/usb.h>
 #include <linux/usbdevice_fs.h>
+#include <linux/cdev.h>
 #include <asm/uaccess.h>
 #include <asm/byteorder.h>
 #include <linux/moduleparam.h>
@@ -50,6 +51,10 @@
 #include "hcd.h"	/* for usbcore internals */
 #include "usb.h"
 
+#define USB_MAXBUS			64
+#define USB_DEVICE_MAX			USB_MAXBUS * 128
+static struct class *usb_device_class;
+
 struct async {
 	struct list_head asynclist;
 	struct dev_state *ps;
@@ -487,7 +492,7 @@ static int check_ctrlrecip(struct dev_state *ps, unsigned int requesttype, unsig
  */
 static int usbdev_open(struct inode *inode, struct file *file)
 {
-	struct usb_device *dev;
+	struct usb_device *dev = NULL;
 	struct dev_state *ps;
 	int ret;
 
@@ -501,11 +506,16 @@ static int usbdev_open(struct inode *inode, struct file *file)
 
 	lock_kernel();
 	ret = -ENOENT;
-	dev = usb_get_dev(inode->u.generic_ip);
+	/* check if we are called from a real node or usbfs */
+	if (imajor(inode) == USB_DEVICE_MAJOR)
+		dev = usbdev_lookup_minor(iminor(inode));
+	if (!dev)
+		dev = inode->u.generic_ip;
 	if (!dev) {
 		kfree(ps);
 		goto out;
 	}
+	usb_get_dev(dev);
 	ret = 0;
 	ps->dev = dev;
 	ps->file = file;
@@ -1477,3 +1487,80 @@ struct file_operations usbfs_device_file_operations = {
 	.open =		usbdev_open,
 	.release =	usbdev_release,
 };
+
+struct usb_device *usbdev_lookup_minor(int minor)
+{
+	struct class_device *class_dev;
+	struct usb_device *dev = NULL;
+
+	down(&usb_device_class->sem);
+	list_for_each_entry(class_dev, &usb_device_class->children, node) {
+		if (class_dev->devt == MKDEV(USB_DEVICE_MAJOR, minor)) {
+			dev = class_dev->class_data;
+			break;
+		}
+	}
+	up(&usb_device_class->sem);
+
+	return dev;
+};
+
+void usbdev_add(struct usb_device *dev)
+{
+	int minor = ((dev->bus->busnum-1) * 128) + (dev->devnum-1);
+
+	dev->class_dev = class_device_create(usb_device_class,
+				MKDEV(USB_DEVICE_MAJOR, minor), &dev->dev,
+				"usbdev%d.%d", dev->bus->busnum, dev->devnum);
+
+	dev->class_dev->class_data = dev;
+}
+
+void usbdev_remove(struct usb_device *dev)
+{
+	class_device_unregister(dev->class_dev);
+}
+
+static struct cdev usb_device_cdev = {
+	.kobj   = {.name = "usb_device", },
+	.owner  = THIS_MODULE,
+};
+
+int __init usbdev_init(void)
+{
+	int retval;
+
+	retval = register_chrdev_region(MKDEV(USB_DEVICE_MAJOR, 0),
+				        USB_DEVICE_MAX, "usb_device");
+	if (retval) {
+		err("unable to register minors for usb_device");
+		goto out;
+	}
+	cdev_init(&usb_device_cdev, &usbfs_device_file_operations);
+	retval = cdev_add(&usb_device_cdev,
+			  MKDEV(USB_DEVICE_MAJOR, 0), USB_DEVICE_MAX);
+	if (retval) {
+		err("unable to get usb_device major %d", USB_DEVICE_MAJOR);
+		unregister_chrdev_region(USB_DEVICE_MAJOR, USB_DEVICE_MAX);
+		goto out;
+	}
+	usb_device_class = class_create(THIS_MODULE, "usb_device");
+	if (IS_ERR(usb_device_class)) {
+		err("unable to register usb_device class");
+		retval = PTR_ERR(usb_device_class);
+		usb_device_class = NULL;
+		cdev_del(&usb_device_cdev);
+		unregister_chrdev_region(USB_DEVICE_MAJOR, USB_DEVICE_MAX);
+	}
+
+out:
+	return retval;
+}
+
+void usbdev_cleanup(void)
+{
+	class_destroy(usb_device_class);
+	cdev_del(&usb_device_cdev);
+	unregister_chrdev_region(USB_DEVICE_MAJOR, USB_DEVICE_MAX);
+}
+

drivers/usb/core/hub.c

@@ -1051,6 +1051,7 @@ void usb_disconnect(struct usb_device **pdev)
 	dev_dbg (&udev->dev, "unregistering device\n");
 	release_address(udev);
 	usbfs_remove_device(udev);
+	usbdev_remove(udev);
 	usb_remove_sysfs_dev_files(udev);
 
 	/* Avoid races with recursively_mark_NOTATTACHED() */
@@ -1290,6 +1291,7 @@ int usb_new_device(struct usb_device *udev)
 	/* USB device state == configured ... usable */
 
 	/* add a /proc/bus/usb entry */
+	usbdev_add(udev);
 	usbfs_add_device(udev);
 	return 0;
 

drivers/usb/core/inode.c

@@ -728,15 +728,9 @@ int __init usbfs_init(void)
 {
 	int retval;
 
-	retval = usb_register(&usbfs_driver);
-	if (retval)
-		return retval;
-
 	retval = register_filesystem(&usb_fs_type);
-	if (retval) {
-		usb_deregister(&usbfs_driver);
+	if (retval)
 		return retval;
-	}
 
 	/* create mount point for usbfs */
 	usbdir = proc_mkdir("usb", proc_bus);
@@ -746,7 +740,6 @@ int __init usbfs_init(void)
 
 void usbfs_cleanup(void)
 {
-	usb_deregister(&usbfs_driver);
 	unregister_filesystem(&usb_fs_type);
 	if (usbdir)
 		remove_proc_entry("usb", proc_bus);

drivers/usb/core/usb.c

@@ -1478,13 +1478,18 @@ static int __init usb_init(void)
 	retval = usb_major_init();
 	if (retval)
 		goto major_init_failed;
+	retval = usb_register(&usbfs_driver);
+	if (retval)
+		goto driver_register_failed;
+	retval = usbdev_init();
+	if (retval)
+		goto usbdevice_init_failed;
 	retval = usbfs_init();
 	if (retval)
 		goto fs_init_failed;
 	retval = usb_hub_init();
 	if (retval)
 		goto hub_init_failed;
-
 	retval = driver_register(&usb_generic_driver);
 	if (!retval)
 		goto out;
@@ -1493,6 +1498,10 @@ static int __init usb_init(void)
 hub_init_failed:
 	usbfs_cleanup();
 fs_init_failed:
+	usbdev_cleanup();
+usbdevice_init_failed:
+	usb_deregister(&usbfs_driver);
+driver_register_failed:
 	usb_major_cleanup();
 major_init_failed:
 	usb_host_cleanup();
@@ -1514,6 +1523,8 @@ static void __exit usb_exit(void)
 	driver_unregister(&usb_generic_driver);
 	usb_major_cleanup();
 	usbfs_cleanup();
+	usb_deregister(&usbfs_driver);
+	usbdev_cleanup();
 	usb_hub_cleanup();
 	usb_host_cleanup();
 	bus_unregister(&usb_bus_type);

drivers/usb/core/usb.h

@@ -37,6 +37,11 @@ extern struct file_operations usbfs_devices_fops;
 extern struct file_operations usbfs_device_file_operations;
 extern void usbfs_conn_disc_event(void);
 
+extern int usbdev_init(void);
+extern void usbdev_cleanup(void);
+extern void usbdev_add(struct usb_device *dev);
+extern void usbdev_remove(struct usb_device *dev);
+extern struct usb_device *usbdev_lookup_minor(int minor);
 
 struct dev_state {
 	struct list_head list;      /* state list */

include/linux/usb.h

@@ -5,6 +5,7 @@
 #include <linux/usb_ch9.h>
 
 #define USB_MAJOR			180
+#define USB_DEVICE_MAJOR		189
 
 
 #ifdef __KERNEL__
@@ -349,6 +350,7 @@ struct usb_device {
 	char *manufacturer;
 	char *serial;			/* static strings from the device */
 	struct list_head filelist;
+	struct class_device *class_dev;
 	struct dentry *usbfs_dentry;	/* usbfs dentry entry for the device */
 
 	/*