drivers/usb/usbip/stub_dev.c - linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0+
 /*
  * Copyright (C) 2003-2008 Takahiro Hirofuchi
  */

 #include <linux/device.h>
 #include <linux/file.h>
 #include <linux/kthread.h>
 #include <linux/module.h>

 #include "usbip_common.h"
 #include "stub.h"

 /*
  * usbip_status shows the status of usbip-host as long as this driver is bound
  * to the target device.
  */
 static ssize_t usbip_status_show(struct device *dev,
 				 struct device_attribute *attr, char *buf)
 {
 	struct stub_device *sdev = dev_get_drvdata(dev);
 	int status;

 	if (!sdev) {
 		dev_err(dev, "sdev is null\n");
 		return -ENODEV;
 	}

 	spin_lock_irq(&sdev->ud.lock);
 	status = sdev->ud.status;
 	spin_unlock_irq(&sdev->ud.lock);

 	return sysfs_emit(buf, "%d\n", status);
 }
 static DEVICE_ATTR_RO(usbip_status);

 /*
  * usbip_sockfd gets a socket descriptor of an established TCP connection that
  * is used to transfer usbip requests by kernel threads. -1 is a magic number
  * by which usbip connection is finished.
  */
 static ssize_t usbip_sockfd_store(struct device *dev, struct device_attribute *attr,
 			    const char *buf, size_t count)
 {
 	struct stub_device *sdev = dev_get_drvdata(dev);
 	int sockfd = 0;
 	struct socket *socket;
 	int rv;
 	struct task_struct *tcp_rx = NULL;
 	struct task_struct *tcp_tx = NULL;

 	if (!sdev) {
 		dev_err(dev, "sdev is null\n");
 		return -ENODEV;
 	}

 	rv = sscanf(buf, "%d", &sockfd);
 	if (rv != 1)
 		return -EINVAL;

 	if (sockfd != -1) {
 		int err;

 		dev_info(dev, "stub up\n");

 		mutex_lock(&sdev->ud.sysfs_lock);
 		spin_lock_irq(&sdev->ud.lock);

 		if (sdev->ud.status != SDEV_ST_AVAILABLE) {
 			dev_err(dev, "not ready\n");
 			goto err;
 		}

 		socket = sockfd_lookup(sockfd, &err);
 		if (!socket) {
 			dev_err(dev, "failed to lookup sock");
 			goto err;
 		}

 		if (socket->type != SOCK_STREAM) {
 			dev_err(dev, "Expecting SOCK_STREAM - found %d",
 				socket->type);
 			goto sock_err;
 		}

 		/* unlock and create threads and get tasks */
 		spin_unlock_irq(&sdev->ud.lock);
 		tcp_rx = kthread_create(stub_rx_loop, &sdev->ud, "stub_rx");
 		if (IS_ERR(tcp_rx)) {
 			sockfd_put(socket);
 			goto unlock_mutex;
 		}
 		tcp_tx = kthread_create(stub_tx_loop, &sdev->ud, "stub_tx");
 		if (IS_ERR(tcp_tx)) {
 			kthread_stop(tcp_rx);
 			sockfd_put(socket);
 			goto unlock_mutex;
 		}

 		/* get task structs now */
 		get_task_struct(tcp_rx);
 		get_task_struct(tcp_tx);

 		/* lock and update sdev->ud state */
 		spin_lock_irq(&sdev->ud.lock);
 		sdev->ud.tcp_socket = socket;
 		sdev->ud.sockfd = sockfd;
 		sdev->ud.tcp_rx = tcp_rx;
 		sdev->ud.tcp_tx = tcp_tx;
 		sdev->ud.status = SDEV_ST_USED;
 		spin_unlock_irq(&sdev->ud.lock);

 		wake_up_process(sdev->ud.tcp_rx);
 		wake_up_process(sdev->ud.tcp_tx);

 		mutex_unlock(&sdev->ud.sysfs_lock);

 	} else {
 		dev_info(dev, "stub down\n");

 		mutex_lock(&sdev->ud.sysfs_lock);

 		spin_lock_irq(&sdev->ud.lock);
 		if (sdev->ud.status != SDEV_ST_USED)
 			goto err;

 		spin_unlock_irq(&sdev->ud.lock);

 		usbip_event_add(&sdev->ud, SDEV_EVENT_DOWN);
 		mutex_unlock(&sdev->ud.sysfs_lock);
 	}

 	return count;

 sock_err:
 	sockfd_put(socket);
 err:
 	spin_unlock_irq(&sdev->ud.lock);
 unlock_mutex:
 	mutex_unlock(&sdev->ud.sysfs_lock);
 	return -EINVAL;
 }
 static DEVICE_ATTR_WO(usbip_sockfd);

 static struct attribute *usbip_attrs[] = {
 	&dev_attr_usbip_status.attr,
 	&dev_attr_usbip_sockfd.attr,
 	&dev_attr_usbip_debug.attr,
 	NULL,
 };
 ATTRIBUTE_GROUPS(usbip);

 static void stub_shutdown_connection(struct usbip_device *ud)
 {
 	struct stub_device *sdev = container_of(ud, struct stub_device, ud);

 	/*
 	 * When removing an exported device, kernel panic sometimes occurred
 	 * and then EIP was sk_wait_data of stub_rx thread. Is this because
 	 * sk_wait_data returned though stub_rx thread was already finished by
 	 * step 1?
 	 */
 	if (ud->tcp_socket) {
 		dev_dbg(&sdev->udev->dev, "shutdown sockfd %d\n", ud->sockfd);
 		kernel_sock_shutdown(ud->tcp_socket, SHUT_RDWR);
 	}

 	/* 1. stop threads */
 	if (ud->tcp_rx) {
 		kthread_stop_put(ud->tcp_rx);
 		ud->tcp_rx = NULL;
 	}
 	if (ud->tcp_tx) {
 		kthread_stop_put(ud->tcp_tx);
 		ud->tcp_tx = NULL;
 	}

 	/*
 	 * 2. close the socket
 	 *
 	 * tcp_socket is freed after threads are killed so that usbip_xmit does
 	 * not touch NULL socket.
 	 */
 	if (ud->tcp_socket) {
 		sockfd_put(ud->tcp_socket);
 		ud->tcp_socket = NULL;
 		ud->sockfd = -1;
 	}

 	/* 3. free used data */
 	stub_device_cleanup_urbs(sdev);

 	/* 4. free stub_unlink */
 	{
 		unsigned long flags;
 		struct stub_unlink *unlink, *tmp;

 		spin_lock_irqsave(&sdev->priv_lock, flags);
 		list_for_each_entry_safe(unlink, tmp, &sdev->unlink_tx, list) {
 			list_del(&unlink->list);
 			kfree(unlink);
 		}
 		list_for_each_entry_safe(unlink, tmp, &sdev->unlink_free,
 					 list) {
 			list_del(&unlink->list);
 			kfree(unlink);
 		}
 		spin_unlock_irqrestore(&sdev->priv_lock, flags);
 	}
 }

 static void stub_device_reset(struct usbip_device *ud)
 {
 	struct stub_device *sdev = container_of(ud, struct stub_device, ud);
 	struct usb_device *udev = sdev->udev;
 	int ret;

 	dev_dbg(&udev->dev, "device reset");

 	ret = usb_lock_device_for_reset(udev, NULL);
 	if (ret < 0) {
 		dev_err(&udev->dev, "lock for reset\n");
 		spin_lock_irq(&ud->lock);
 		ud->status = SDEV_ST_ERROR;
 		spin_unlock_irq(&ud->lock);
 		return;
 	}

 	/* try to reset the device */
 	ret = usb_reset_device(udev);
 	usb_unlock_device(udev);

 	spin_lock_irq(&ud->lock);
 	if (ret) {
 		dev_err(&udev->dev, "device reset\n");
 		ud->status = SDEV_ST_ERROR;
 	} else {
 		dev_info(&udev->dev, "device reset\n");
 		ud->status = SDEV_ST_AVAILABLE;
 	}
 	spin_unlock_irq(&ud->lock);
 }

 static void stub_device_unusable(struct usbip_device *ud)
 {
 	spin_lock_irq(&ud->lock);
 	ud->status = SDEV_ST_ERROR;
 	spin_unlock_irq(&ud->lock);
 }

 /**
  * stub_device_alloc - allocate a new stub_device struct
  * @udev: usb_device of a new device
  *
  * Allocates and initializes a new stub_device struct.
  */
 static struct stub_device *stub_device_alloc(struct usb_device *udev)
 {
 	struct stub_device *sdev;
 	int busnum = udev->bus->busnum;
 	int devnum = udev->devnum;

 	dev_dbg(&udev->dev, "allocating stub device");

 	/* yes, it's a new device */
 	sdev = kzalloc(sizeof(struct stub_device), GFP_KERNEL);
 	if (!sdev)
 		return NULL;

 	sdev->udev = usb_get_dev(udev);

 	/*
 	 * devid is defined with devnum when this driver is first allocated.
 	 * devnum may change later if a device is reset. However, devid never
 	 * changes during a usbip connection.
 	 */
 	sdev->devid		= (busnum << 16) | devnum;
 	sdev->ud.side		= USBIP_STUB;
 	sdev->ud.status		= SDEV_ST_AVAILABLE;
 	spin_lock_init(&sdev->ud.lock);
 	mutex_init(&sdev->ud.sysfs_lock);
 	sdev->ud.tcp_socket	= NULL;
 	sdev->ud.sockfd		= -1;

 	INIT_LIST_HEAD(&sdev->priv_init);
 	INIT_LIST_HEAD(&sdev->priv_tx);
 	INIT_LIST_HEAD(&sdev->priv_free);
 	INIT_LIST_HEAD(&sdev->unlink_free);
 	INIT_LIST_HEAD(&sdev->unlink_tx);
 	spin_lock_init(&sdev->priv_lock);

 	init_waitqueue_head(&sdev->tx_waitq);

 	sdev->ud.eh_ops.shutdown = stub_shutdown_connection;
 	sdev->ud.eh_ops.reset    = stub_device_reset;
 	sdev->ud.eh_ops.unusable = stub_device_unusable;

 	usbip_start_eh(&sdev->ud);

 	dev_dbg(&udev->dev, "register new device\n");

 	return sdev;
 }

 static void stub_device_free(struct stub_device *sdev)
 {
 	kfree(sdev);
 }

 static int stub_probe(struct usb_device *udev)
 {
 	struct stub_device *sdev = NULL;
 	const char *udev_busid = dev_name(&udev->dev);
 	struct bus_id_priv *busid_priv;
 	int rc = 0;
 	char save_status;

 	dev_dbg(&udev->dev, "Enter probe\n");

 	/* Not sure if this is our device. Allocate here to avoid
 	 * calling alloc while holding busid_table lock.
 	 */
 	sdev = stub_device_alloc(udev);
 	if (!sdev)
 		return -ENOMEM;

 	/* check we should claim or not by busid_table */
 	busid_priv = get_busid_priv(udev_busid);
 	if (!busid_priv || (busid_priv->status == STUB_BUSID_REMOV) ||
 	    (busid_priv->status == STUB_BUSID_OTHER)) {
 		dev_info(&udev->dev,
 			"%s is not in match_busid table... skip!\n",
 			udev_busid);

 		/*
 		 * Return value should be ENODEV or ENOXIO to continue trying
 		 * other matched drivers by the driver core.
 		 * See driver_probe_device() in driver/base/dd.c
 		 */
 		rc = -ENODEV;
 		if (!busid_priv)
 			goto sdev_free;

 		goto call_put_busid_priv;
 	}

 	if (udev->descriptor.bDeviceClass == USB_CLASS_HUB) {
 		dev_dbg(&udev->dev, "%s is a usb hub device... skip!\n",
 			 udev_busid);
 		rc = -ENODEV;
 		goto call_put_busid_priv;
 	}

 	if (!strcmp(udev->bus->bus_name, "vhci_hcd")) {
 		dev_dbg(&udev->dev,
 			"%s is attached on vhci_hcd... skip!\n",
 			udev_busid);

 		rc = -ENODEV;
 		goto call_put_busid_priv;
 	}


 	dev_info(&udev->dev,
 		"usbip-host: register new device (bus %u dev %u)\n",
 		udev->bus->busnum, udev->devnum);

 	busid_priv->shutdown_busid = 0;

 	/* set private data to usb_device */
 	dev_set_drvdata(&udev->dev, sdev);

 	busid_priv->sdev = sdev;
 	busid_priv->udev = udev;

 	save_status = busid_priv->status;
 	busid_priv->status = STUB_BUSID_ALLOC;

 	/* release the busid_lock */
 	put_busid_priv(busid_priv);

 	/*
 	 * Claim this hub port.
 	 * It doesn't matter what value we pass as owner
 	 * (struct dev_state) as long as it is unique.
 	 */
 	rc = usb_hub_claim_port(udev->parent, udev->portnum,
 			(struct usb_dev_state *) udev);
 	if (rc) {
 		dev_dbg(&udev->dev, "unable to claim port\n");
 		goto err_port;
 	}

 	return 0;

 err_port:
 	dev_set_drvdata(&udev->dev, NULL);

 	/* we already have busid_priv, just lock busid_lock */
 	spin_lock(&busid_priv->busid_lock);
 	busid_priv->sdev = NULL;
 	busid_priv->status = save_status;
 	spin_unlock(&busid_priv->busid_lock);
 	/* lock is released - go to free */
 	goto sdev_free;

 call_put_busid_priv:
 	/* release the busid_lock */
 	put_busid_priv(busid_priv);

 sdev_free:
 	usb_put_dev(udev);
 	stub_device_free(sdev);

 	return rc;
 }

 static void shutdown_busid(struct bus_id_priv *busid_priv)
 {
 	usbip_event_add(&busid_priv->sdev->ud, SDEV_EVENT_REMOVED);

 	/* wait for the stop of the event handler */
 	usbip_stop_eh(&busid_priv->sdev->ud);
 }

 /*
  * called in usb_disconnect() or usb_deregister()
  * but only if actconfig(active configuration) exists
  */
 static void stub_disconnect(struct usb_device *udev)
 {
 	struct stub_device *sdev;
 	const char *udev_busid = dev_name(&udev->dev);
 	struct bus_id_priv *busid_priv;
 	int rc;

 	dev_dbg(&udev->dev, "Enter disconnect\n");

 	busid_priv = get_busid_priv(udev_busid);
 	if (!busid_priv) {
 		BUG();
 		return;
 	}

 	sdev = dev_get_drvdata(&udev->dev);

 	/* get stub_device */
 	if (!sdev) {
 		dev_err(&udev->dev, "could not get device");
 		/* release busid_lock */
 		put_busid_priv(busid_priv);
 		return;
 	}

 	dev_set_drvdata(&udev->dev, NULL);

 	/* release busid_lock before call to remove device files */
 	put_busid_priv(busid_priv);

 	/*
 	 * NOTE: rx/tx threads are invoked for each usb_device.
 	 */

 	/* release port */
 	rc = usb_hub_release_port(udev->parent, udev->portnum,
 				  (struct usb_dev_state *) udev);
 	if (rc) {
 		dev_dbg(&udev->dev, "unable to release port\n");
 		return;
 	}

 	/* If usb reset is called from event handler */
 	if (usbip_in_eh(current))
 		return;

 	/* we already have busid_priv, just lock busid_lock */
 	spin_lock(&busid_priv->busid_lock);
 	if (!busid_priv->shutdown_busid)
 		busid_priv->shutdown_busid = 1;
 	/* release busid_lock */
 	spin_unlock(&busid_priv->busid_lock);

 	/* shutdown the current connection */
 	shutdown_busid(busid_priv);

 	usb_put_dev(sdev->udev);

 	/* we already have busid_priv, just lock busid_lock */
 	spin_lock(&busid_priv->busid_lock);
 	/* free sdev */
 	busid_priv->sdev = NULL;
 	stub_device_free(sdev);

 	if (busid_priv->status == STUB_BUSID_ALLOC)
 		busid_priv->status = STUB_BUSID_ADDED;
 	/* release busid_lock */
 	spin_unlock(&busid_priv->busid_lock);
 	return;
 }

 #ifdef CONFIG_PM

 /* These functions need usb_port_suspend and usb_port_resume,
  * which reside in drivers/usb/core/usb.h. Skip for now. */

 static int stub_suspend(struct usb_device *udev, pm_message_t message)
 {
 	dev_dbg(&udev->dev, "stub_suspend\n");

 	return 0;
 }

 static int stub_resume(struct usb_device *udev, pm_message_t message)
 {
 	dev_dbg(&udev->dev, "stub_resume\n");

 	return 0;
 }

 #endif	/* CONFIG_PM */

 struct usb_device_driver stub_driver = {
 	.name		= "usbip-host",
 	.probe		= stub_probe,
 	.disconnect	= stub_disconnect,
 #ifdef CONFIG_PM
 	.suspend	= stub_suspend,
 	.resume		= stub_resume,
 #endif
 	.supports_autosuspend	=	0,
 	.dev_groups	= usbip_groups,
 };
	// SPDX-License-Identifier: GPL-2.0+
	/*
	* Copyright (C) 2003-2008 Takahiro Hirofuchi
	*/

	#include <linux/device.h>
	#include <linux/file.h>
	#include <linux/kthread.h>
	#include <linux/module.h>

	#include "usbip_common.h"
	#include "stub.h"

	/*
	* usbip_status shows the status of usbip-host as long as this driver is bound
	* to the target device.
	*/
	static ssize_t usbip_status_show(struct device *dev,
	struct device_attribute attr, char buf)
	{
	struct stub_device *sdev = dev_get_drvdata(dev);
	int status;

	if (!sdev) {
	dev_err(dev, "sdev is null\n");
	return -ENODEV;
	}

	spin_lock_irq(&sdev->ud.lock);
	status = sdev->ud.status;
	spin_unlock_irq(&sdev->ud.lock);

	return sysfs_emit(buf, "%d\n", status);
	}
	static DEVICE_ATTR_RO(usbip_status);

	/*
	* usbip_sockfd gets a socket descriptor of an established TCP connection that
	* is used to transfer usbip requests by kernel threads. -1 is a magic number
	* by which usbip connection is finished.
	*/
	static ssize_t usbip_sockfd_store(struct device dev, struct device_attribute attr,
	const char *buf, size_t count)
	{
	struct stub_device *sdev = dev_get_drvdata(dev);
	int sockfd = 0;
	struct socket *socket;
	int rv;
	struct task_struct *tcp_rx = NULL;
	struct task_struct *tcp_tx = NULL;

	if (!sdev) {
	dev_err(dev, "sdev is null\n");
	return -ENODEV;
	}

	rv = sscanf(buf, "%d", &sockfd);
	if (rv != 1)
	return -EINVAL;

	if (sockfd != -1) {
	int err;

	dev_info(dev, "stub up\n");

	mutex_lock(&sdev->ud.sysfs_lock);
	spin_lock_irq(&sdev->ud.lock);

	if (sdev->ud.status != SDEV_ST_AVAILABLE) {
	dev_err(dev, "not ready\n");
	goto err;
	}

	socket = sockfd_lookup(sockfd, &err);
	if (!socket) {
	dev_err(dev, "failed to lookup sock");
	goto err;
	}

	if (socket->type != SOCK_STREAM) {
	dev_err(dev, "Expecting SOCK_STREAM - found %d",
	socket->type);
	goto sock_err;
	}

	/* unlock and create threads and get tasks */
	spin_unlock_irq(&sdev->ud.lock);
	tcp_rx = kthread_create(stub_rx_loop, &sdev->ud, "stub_rx");
	if (IS_ERR(tcp_rx)) {
	sockfd_put(socket);
	goto unlock_mutex;
	}
	tcp_tx = kthread_create(stub_tx_loop, &sdev->ud, "stub_tx");
	if (IS_ERR(tcp_tx)) {
	kthread_stop(tcp_rx);
	sockfd_put(socket);
	goto unlock_mutex;
	}

	/* get task structs now */
	get_task_struct(tcp_rx);
	get_task_struct(tcp_tx);

	/* lock and update sdev->ud state */
	spin_lock_irq(&sdev->ud.lock);
	sdev->ud.tcp_socket = socket;
	sdev->ud.sockfd = sockfd;
	sdev->ud.tcp_rx = tcp_rx;
	sdev->ud.tcp_tx = tcp_tx;
	sdev->ud.status = SDEV_ST_USED;
	spin_unlock_irq(&sdev->ud.lock);

	wake_up_process(sdev->ud.tcp_rx);
	wake_up_process(sdev->ud.tcp_tx);

	mutex_unlock(&sdev->ud.sysfs_lock);

	} else {
	dev_info(dev, "stub down\n");

	mutex_lock(&sdev->ud.sysfs_lock);

	spin_lock_irq(&sdev->ud.lock);
	if (sdev->ud.status != SDEV_ST_USED)
	goto err;

	spin_unlock_irq(&sdev->ud.lock);

	usbip_event_add(&sdev->ud, SDEV_EVENT_DOWN);
	mutex_unlock(&sdev->ud.sysfs_lock);
	}

	return count;

	sock_err:
	sockfd_put(socket);
	err:
	spin_unlock_irq(&sdev->ud.lock);
	unlock_mutex:
	mutex_unlock(&sdev->ud.sysfs_lock);
	return -EINVAL;
	}
	static DEVICE_ATTR_WO(usbip_sockfd);

	static struct attribute *usbip_attrs[] = {
	&dev_attr_usbip_status.attr,
	&dev_attr_usbip_sockfd.attr,
	&dev_attr_usbip_debug.attr,
	NULL,
	};
	ATTRIBUTE_GROUPS(usbip);

	static void stub_shutdown_connection(struct usbip_device *ud)
	{
	struct stub_device *sdev = container_of(ud, struct stub_device, ud);

	/*
	* When removing an exported device, kernel panic sometimes occurred
	* and then EIP was sk_wait_data of stub_rx thread. Is this because
	* sk_wait_data returned though stub_rx thread was already finished by
	* step 1?
	*/
	if (ud->tcp_socket) {
	dev_dbg(&sdev->udev->dev, "shutdown sockfd %d\n", ud->sockfd);
	kernel_sock_shutdown(ud->tcp_socket, SHUT_RDWR);
	}

	/* 1. stop threads */
	if (ud->tcp_rx) {
	kthread_stop_put(ud->tcp_rx);
	ud->tcp_rx = NULL;
	}
	if (ud->tcp_tx) {
	kthread_stop_put(ud->tcp_tx);
	ud->tcp_tx = NULL;
	}

	/*
	* 2. close the socket
	*
	* tcp_socket is freed after threads are killed so that usbip_xmit does
	* not touch NULL socket.
	*/
	if (ud->tcp_socket) {
	sockfd_put(ud->tcp_socket);
	ud->tcp_socket = NULL;
	ud->sockfd = -1;
	}

	/* 3. free used data */
	stub_device_cleanup_urbs(sdev);

	/* 4. free stub_unlink */
	{
	unsigned long flags;
	struct stub_unlink unlink, tmp;

	spin_lock_irqsave(&sdev->priv_lock, flags);
	list_for_each_entry_safe(unlink, tmp, &sdev->unlink_tx, list) {
	list_del(&unlink->list);
	kfree(unlink);
	}
	list_for_each_entry_safe(unlink, tmp, &sdev->unlink_free,
	list) {
	list_del(&unlink->list);
	kfree(unlink);
	}
	spin_unlock_irqrestore(&sdev->priv_lock, flags);
	}
	}

	static void stub_device_reset(struct usbip_device *ud)
	{
	struct stub_device *sdev = container_of(ud, struct stub_device, ud);
	struct usb_device *udev = sdev->udev;
	int ret;

	dev_dbg(&udev->dev, "device reset");

	ret = usb_lock_device_for_reset(udev, NULL);
	if (ret < 0) {
	dev_err(&udev->dev, "lock for reset\n");
	spin_lock_irq(&ud->lock);
	ud->status = SDEV_ST_ERROR;
	spin_unlock_irq(&ud->lock);
	return;
	}

	/* try to reset the device */
	ret = usb_reset_device(udev);
	usb_unlock_device(udev);

	spin_lock_irq(&ud->lock);
	if (ret) {
	dev_err(&udev->dev, "device reset\n");
	ud->status = SDEV_ST_ERROR;
	} else {
	dev_info(&udev->dev, "device reset\n");
	ud->status = SDEV_ST_AVAILABLE;
	}
	spin_unlock_irq(&ud->lock);
	}

	static void stub_device_unusable(struct usbip_device *ud)
	{
	spin_lock_irq(&ud->lock);
	ud->status = SDEV_ST_ERROR;
	spin_unlock_irq(&ud->lock);
	}

	/**
	* stub_device_alloc - allocate a new stub_device struct
	* @udev: usb_device of a new device
	*
	* Allocates and initializes a new stub_device struct.
	*/
	static struct stub_device stub_device_alloc(struct usb_device udev)
	{
	struct stub_device *sdev;
	int busnum = udev->bus->busnum;
	int devnum = udev->devnum;

	dev_dbg(&udev->dev, "allocating stub device");

	/* yes, it's a new device */
	sdev = kzalloc(sizeof(struct stub_device), GFP_KERNEL);
	if (!sdev)
	return NULL;

	sdev->udev = usb_get_dev(udev);

	/*
	* devid is defined with devnum when this driver is first allocated.
	* devnum may change later if a device is reset. However, devid never
	* changes during a usbip connection.
	*/
	sdev->devid = (busnum << 16) \| devnum;
	sdev->ud.side = USBIP_STUB;
	sdev->ud.status = SDEV_ST_AVAILABLE;
	spin_lock_init(&sdev->ud.lock);
	mutex_init(&sdev->ud.sysfs_lock);
	sdev->ud.tcp_socket = NULL;
	sdev->ud.sockfd = -1;

	INIT_LIST_HEAD(&sdev->priv_init);
	INIT_LIST_HEAD(&sdev->priv_tx);
	INIT_LIST_HEAD(&sdev->priv_free);
	INIT_LIST_HEAD(&sdev->unlink_free);
	INIT_LIST_HEAD(&sdev->unlink_tx);
	spin_lock_init(&sdev->priv_lock);

	init_waitqueue_head(&sdev->tx_waitq);

	sdev->ud.eh_ops.shutdown = stub_shutdown_connection;
	sdev->ud.eh_ops.reset = stub_device_reset;
	sdev->ud.eh_ops.unusable = stub_device_unusable;

	usbip_start_eh(&sdev->ud);

	dev_dbg(&udev->dev, "register new device\n");

	return sdev;
	}

	static void stub_device_free(struct stub_device *sdev)
	{
	kfree(sdev);
	}

	static int stub_probe(struct usb_device *udev)
	{
	struct stub_device *sdev = NULL;
	const char *udev_busid = dev_name(&udev->dev);
	struct bus_id_priv *busid_priv;
	int rc = 0;
	char save_status;

	dev_dbg(&udev->dev, "Enter probe\n");

	/* Not sure if this is our device. Allocate here to avoid
	* calling alloc while holding busid_table lock.
	*/
	sdev = stub_device_alloc(udev);
	if (!sdev)
	return -ENOMEM;

	/* check we should claim or not by busid_table */
	busid_priv = get_busid_priv(udev_busid);
	if (!busid_priv \|\| (busid_priv->status == STUB_BUSID_REMOV) \|\|
	(busid_priv->status == STUB_BUSID_OTHER)) {
	dev_info(&udev->dev,
	"%s is not in match_busid table... skip!\n",
	udev_busid);

	/*
	* Return value should be ENODEV or ENOXIO to continue trying
	* other matched drivers by the driver core.
	* See driver_probe_device() in driver/base/dd.c
	*/
	rc = -ENODEV;
	if (!busid_priv)
	goto sdev_free;

	goto call_put_busid_priv;
	}

	if (udev->descriptor.bDeviceClass == USB_CLASS_HUB) {
	dev_dbg(&udev->dev, "%s is a usb hub device... skip!\n",
	udev_busid);
	rc = -ENODEV;
	goto call_put_busid_priv;
	}

	if (!strcmp(udev->bus->bus_name, "vhci_hcd")) {
	dev_dbg(&udev->dev,
	"%s is attached on vhci_hcd... skip!\n",
	udev_busid);

	rc = -ENODEV;
	goto call_put_busid_priv;
	}


	dev_info(&udev->dev,
	"usbip-host: register new device (bus %u dev %u)\n",
	udev->bus->busnum, udev->devnum);

	busid_priv->shutdown_busid = 0;

	/* set private data to usb_device */
	dev_set_drvdata(&udev->dev, sdev);

	busid_priv->sdev = sdev;
	busid_priv->udev = udev;

	save_status = busid_priv->status;
	busid_priv->status = STUB_BUSID_ALLOC;

	/* release the busid_lock */
	put_busid_priv(busid_priv);

	/*
	* Claim this hub port.
	* It doesn't matter what value we pass as owner
	* (struct dev_state) as long as it is unique.
	*/
	rc = usb_hub_claim_port(udev->parent, udev->portnum,
	(struct usb_dev_state *) udev);
	if (rc) {
	dev_dbg(&udev->dev, "unable to claim port\n");
	goto err_port;
	}

	return 0;

	err_port:
	dev_set_drvdata(&udev->dev, NULL);

	/* we already have busid_priv, just lock busid_lock */
	spin_lock(&busid_priv->busid_lock);
	busid_priv->sdev = NULL;
	busid_priv->status = save_status;
	spin_unlock(&busid_priv->busid_lock);
	/* lock is released - go to free */
	goto sdev_free;

	call_put_busid_priv:
	/* release the busid_lock */
	put_busid_priv(busid_priv);

	sdev_free:
	usb_put_dev(udev);
	stub_device_free(sdev);

	return rc;
	}

	static void shutdown_busid(struct bus_id_priv *busid_priv)
	{
	usbip_event_add(&busid_priv->sdev->ud, SDEV_EVENT_REMOVED);

	/* wait for the stop of the event handler */
	usbip_stop_eh(&busid_priv->sdev->ud);
	}

	/*
	* called in usb_disconnect() or usb_deregister()
	* but only if actconfig(active configuration) exists
	*/
	static void stub_disconnect(struct usb_device *udev)
	{
	struct stub_device *sdev;
	const char *udev_busid = dev_name(&udev->dev);
	struct bus_id_priv *busid_priv;
	int rc;

	dev_dbg(&udev->dev, "Enter disconnect\n");

	busid_priv = get_busid_priv(udev_busid);
	if (!busid_priv) {
	BUG();
	return;
	}

	sdev = dev_get_drvdata(&udev->dev);

	/* get stub_device */
	if (!sdev) {
	dev_err(&udev->dev, "could not get device");
	/* release busid_lock */
	put_busid_priv(busid_priv);
	return;
	}

	dev_set_drvdata(&udev->dev, NULL);

	/* release busid_lock before call to remove device files */
	put_busid_priv(busid_priv);

	/*
	* NOTE: rx/tx threads are invoked for each usb_device.
	*/

	/* release port */
	rc = usb_hub_release_port(udev->parent, udev->portnum,
	(struct usb_dev_state *) udev);
	if (rc) {
	dev_dbg(&udev->dev, "unable to release port\n");
	return;
	}

	/* If usb reset is called from event handler */
	if (usbip_in_eh(current))
	return;

	/* we already have busid_priv, just lock busid_lock */
	spin_lock(&busid_priv->busid_lock);
	if (!busid_priv->shutdown_busid)
	busid_priv->shutdown_busid = 1;
	/* release busid_lock */
	spin_unlock(&busid_priv->busid_lock);

	/* shutdown the current connection */
	shutdown_busid(busid_priv);

	usb_put_dev(sdev->udev);

	/* we already have busid_priv, just lock busid_lock */
	spin_lock(&busid_priv->busid_lock);
	/* free sdev */
	busid_priv->sdev = NULL;
	stub_device_free(sdev);

	if (busid_priv->status == STUB_BUSID_ALLOC)
	busid_priv->status = STUB_BUSID_ADDED;
	/* release busid_lock */
	spin_unlock(&busid_priv->busid_lock);
	return;
	}

	#ifdef CONFIG_PM

	/* These functions need usb_port_suspend and usb_port_resume,
	* which reside in drivers/usb/core/usb.h. Skip for now. */

	static int stub_suspend(struct usb_device *udev, pm_message_t message)
	{
	dev_dbg(&udev->dev, "stub_suspend\n");

	return 0;
	}

	static int stub_resume(struct usb_device *udev, pm_message_t message)
	{
	dev_dbg(&udev->dev, "stub_resume\n");

	return 0;
	}

	#endif /* CONFIG_PM */

	struct usb_device_driver stub_driver = {
	.name = "usbip-host",
	.probe = stub_probe,
	.disconnect = stub_disconnect,
	#ifdef CONFIG_PM
	.suspend = stub_suspend,
	.resume = stub_resume,
	#endif
	.supports_autosuspend = 0,
	.dev_groups = usbip_groups,
	};