[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>

1 files changed, 89 insertions, 2 deletions

diff --git a/drivers/usb/core/devio.c b/drivers/usb/core/devio.c
index f86bf1454e21e..d12bc5e84a1a3 100644
--- a/drivers/usb/core/devio.c
+++ b/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);
+}
+