text: /*
   * The USB Monitor, inspired by Dave Harding's USBMon.
   *
   * mon_main.c: Main file, module initiation and exit, registrations, etc.
   *
   * Copyright (C) 2005 Pete Zaitcev (zaitcev@redhat.com)
   */
  
  #include <linux/kernel.h>
  #include <linux/module.h>
  #include <linux/usb.h>
  #include <linux/notifier.h>
  #include <linux/mutex.h>
  
  #include "usb_mon.h"
  #include "../core/hcd.h"
  
  static void mon_stop(struct mon_bus *mbus);
  static void mon_dissolve(struct mon_bus *mbus, struct usb_bus *ubus);
  static void mon_bus_drop(struct kref *r);
  static void mon_bus_init(struct usb_bus *ubus);
  
  DEFINE_MUTEX(mon_lock);
  
  struct mon_bus mon_bus0;		/* Pseudo bus meaning "all buses" */
  static LIST_HEAD(mon_buses);		/* All buses we know: struct mon_bus */
  
  /*
   * Link a reader into the bus.
   *
   * This must be called with mon_lock taken because of mbus->ref.
   */
  void mon_reader_add(struct mon_bus *mbus, struct mon_reader *r)
  {
  	unsigned long flags;
  	struct list_head *p;
  
  	spin_lock_irqsave(&mbus->lock, flags);
  	if (mbus->nreaders == 0) {
  		if (mbus == &mon_bus0) {
  			list_for_each (p, &mon_buses) {
  				struct mon_bus *m1;
  				m1 = list_entry(p, struct mon_bus, bus_link);
  				m1->u_bus->monitored = 1;
  			}
  		} else {
  			mbus->u_bus->monitored = 1;
  		}
  	}
  	mbus->nreaders++;
  	list_add_tail(&r->r_link, &mbus->r_list);
  	spin_unlock_irqrestore(&mbus->lock, flags);
  
  	kref_get(&mbus->ref);
  }
  
  /*
   * Unlink reader from the bus.
   *
   * This is called with mon_lock taken, so we can decrement mbus->ref.
   */
  void mon_reader_del(struct mon_bus *mbus, struct mon_reader *r)
  {
  	unsigned long flags;
  
  	spin_lock_irqsave(&mbus->lock, flags);
  	list_del(&r->r_link);
  	--mbus->nreaders;
  	if (mbus->nreaders == 0)
  		mon_stop(mbus);
  	spin_unlock_irqrestore(&mbus->lock, flags);
  
  	kref_put(&mbus->ref, mon_bus_drop);
  }
  
  /*
   */
  static void mon_bus_submit(struct mon_bus *mbus, struct urb *urb)
  {
  	unsigned long flags;
  	struct list_head *pos;
  	struct mon_reader *r;
  
  	spin_lock_irqsave(&mbus->lock, flags);
  	mbus->cnt_events++;
  	list_for_each (pos, &mbus->r_list) {
  		r = list_entry(pos, struct mon_reader, r_link);
  		r->rnf_submit(r->r_data, urb);
  	}
  	spin_unlock_irqrestore(&mbus->lock, flags);
  	return;
  }
  
  static void mon_submit(struct usb_bus *ubus, struct urb *urb)
  {
  	struct mon_bus *mbus;
  
  	if ((mbus = ubus->mon_bus) != NULL)
  		mon_bus_submit(mbus, urb);
  	mon_bus_submit(&mon_bus0, urb);
  }
  
  /*
   */
  static void mon_bus_submit_error(struct mon_bus *mbus, struct urb *urb, int error)
  {
  	unsigned long flags;
  	struct list_head *pos;
  	struct mon_reader *r;
  
  	spin_lock_irqsave(&mbus->lock, flags);
  	mbus->cnt_events++;
  	list_for_each (pos, &mbus->r_list) {
  		r = list_entry(pos, struct mon_reader, r_link);
  		r->rnf_error(r->r_data, urb, error);
  	}
  	spin_unlock_irqrestore(&mbus->lock, flags);
  	return;
  }
  
  static void mon_submit_error(struct usb_bus *ubus, struct urb *urb, int error)
  {
  	struct mon_bus *mbus;
  
  	if ((mbus = ubus->mon_bus) != NULL)
  		mon_bus_submit_error(mbus, urb, error);
  	mon_bus_submit_error(&mon_bus0, urb, error);
  }
  
  /*
   */
  static void mon_bus_complete(struct mon_bus *mbus, struct urb *urb,
  		int status)
  {
  	unsigned long flags;
  	struct list_head *pos;
  	struct mon_reader *r;
  
  	spin_lock_irqsave(&mbus->lock, flags);
  	mbus->cnt_events++;
  	list_for_each (pos, &mbus->r_list) {
  		r = list_entry(pos, struct mon_reader, r_link);
  		r->rnf_complete(r->r_data, urb, status);
  	}
  	spin_unlock_irqrestore(&mbus->lock, flags);
  }
  
  static void mon_complete(struct usb_bus *ubus, struct urb *urb, int status)
  {
  	struct mon_bus *mbus;
  
   	if ((mbus = ubus->mon_bus) != NULL)
  		mon_bus_complete(mbus, urb, status);
  	mon_bus_complete(&mon_bus0, urb, status);
  }
  
  /* int (*unlink_urb) (struct urb *urb, int status); */
  
  /*
   * Stop monitoring.
   */
  static void mon_stop(struct mon_bus *mbus)
  {
  	struct usb_bus *ubus;
  	struct list_head *p;
  
  	if (mbus == &mon_bus0) {
  		list_for_each (p, &mon_buses) {
  			mbus = list_entry(p, struct mon_bus, bus_link);
  			/*
  			 * We do not change nreaders here, so rely on mon_lock.
  			 */
  			if (mbus->nreaders == 0 && (ubus = mbus->u_bus) != NULL)
  				ubus->monitored = 0;
  		}
  	} else {
  		/*
  		 * A stop can be called for a dissolved mon_bus in case of
  		 * a reader staying across an rmmod foo_hcd, so test ->u_bus.
  		 */
  		if (mon_bus0.nreaders == 0 && (ubus = mbus->u_bus) != NULL) {
  			ubus->monitored = 0;
  			mb();
  		}
  	}
  }
  
  /*
   * Add a USB bus (usually by a modprobe foo-hcd)
   *
   * This does not return an error code because the core cannot care less
   * if monitoring is not established.
   */
  static void mon_bus_add(struct usb_bus *ubus)
  {
  	mon_bus_init(ubus);
  	mutex_lock(&mon_lock);
  	if (mon_bus0.nreaders != 0)
  		ubus->monitored = 1;
  	mutex_unlock(&mon_lock);
  }
  
  /*
   * Remove a USB bus (either from rmmod foo-hcd or from a hot-remove event).
   */
  static void mon_bus_remove(struct usb_bus *ubus)
  {
  	struct mon_bus *mbus = ubus->mon_bus;
  
  	mutex_lock(&mon_lock);
  	list_del(&mbus->bus_link);
  	if (mbus->text_inited)
  		mon_text_del(mbus);
  	if (mbus->bin_inited)
  		mon_bin_del(mbus);
  
  	mon_dissolve(mbus, ubus);
  	kref_put(&mbus->ref, mon_bus_drop);
  	mutex_unlock(&mon_lock);
  }
  
  static int mon_notify(struct notifier_block *self, unsigned long action,
  		      void *dev)
  {
  	switch (action) {
  	case USB_BUS_ADD:
  		mon_bus_add(dev);
  		break;
  	case USB_BUS_REMOVE:
  		mon_bus_remove(dev);
  	}
  	return NOTIFY_OK;
  }
  
  static struct notifier_block mon_nb = {
  	.notifier_call = 	mon_notify,
  };
  
  /*
   * Ops
   */
  static struct usb_mon_operations mon_ops_0 = {
  	.urb_submit =	mon_submit,
  	.urb_submit_error = mon_submit_error,
  	.urb_complete =	mon_complete,
  };
  
  /*
   * Tear usb_bus and mon_bus apart.
   */
  static void mon_dissolve(struct mon_bus *mbus, struct usb_bus *ubus)
  {
  
  	if (ubus->monitored) {
  		ubus->monitored = 0;
  		mb();
  	}
  
  	ubus->mon_bus = NULL;
  	mbus->u_bus = NULL;
  	mb();
  
  	/* We want synchronize_irq() here, but that needs an argument. */
  }
  
  /*
   */
  static void mon_bus_drop(struct kref *r)
  {
  	struct mon_bus *mbus = container_of(r, struct mon_bus, ref);
  	kfree(mbus);
  }
  
  /*
   * Initialize a bus for us:
   *  - allocate mon_bus
   *  - refcount USB bus struct
   *  - link
   */
  static void mon_bus_init(struct usb_bus *ubus)
  {
  	struct mon_bus *mbus;
  
  	if ((mbus = kzalloc(sizeof(struct mon_bus), GFP_KERNEL)) == NULL)
  		goto err_alloc;
  	kref_init(&mbus->ref);
  	spin_lock_init(&mbus->lock);
  	INIT_LIST_HEAD(&mbus->r_list);
  
  	/*
  	 * We don't need to take a reference to ubus, because we receive
  	 * a notification if the bus is about to be removed.
  	 */
  	mbus->u_bus = ubus;
  	ubus->mon_bus = mbus;
  
  	mbus->text_inited = mon_text_add(mbus, ubus);
  	mbus->bin_inited = mon_bin_add(mbus, ubus);
  
  	mutex_lock(&mon_lock);
  	list_add_tail(&mbus->bus_link, &mon_buses);
  	mutex_unlock(&mon_lock);
  	return;
  
  err_alloc:
  	return;
  }
  
  static void mon_bus0_init(void)
  {
  	struct mon_bus *mbus = &mon_bus0;
  
  	kref_init(&mbus->ref);
  	spin_lock_init(&mbus->lock);
  	INIT_LIST_HEAD(&mbus->r_list);
  
  	mbus->text_inited = mon_text_add(mbus, NULL);
  	mbus->bin_inited = mon_bin_add(mbus, NULL);
  }
  
  /*
   * Search a USB bus by number. Notice that USB bus numbers start from one,
   * which we may later use to identify "all" with zero.
   *
   * This function must be called with mon_lock held.
   *
   * This is obviously inefficient and may be revised in the future.
   */
  struct mon_bus *mon_bus_lookup(unsigned int num)
  {
  	struct list_head *p;
  	struct mon_bus *mbus;
  
  	if (num == 0) {
  		return &mon_bus0;
  	}
  	list_for_each (p, &mon_buses) {
  		mbus = list_entry(p, struct mon_bus, bus_link);
  		if (mbus->u_bus->busnum == num) {
  			return mbus;
  		}
  	}
  	return NULL;
  }
  
  static int __init mon_init(void)
  {
  	struct usb_bus *ubus;
  	int rc;
  
  	if ((rc = mon_text_init()) != 0)
  		goto err_text;
  	if ((rc = mon_bin_init()) != 0)
  		goto err_bin;
  
  	mon_bus0_init();
  
  	if (usb_mon_register(&mon_ops_0) != 0) {
  		printk(KERN_NOTICE TAG ": unable to register with the core\n");
  		rc = -ENODEV;
  		goto err_reg;
  	}
  	// MOD_INC_USE_COUNT(which_module?);
  
  	usb_register_notify(&mon_nb);
  
  	mutex_lock(&usb_bus_list_lock);
  	list_for_each_entry (ubus, &usb_bus_list, bus_list) {
  		mon_bus_init(ubus);
  	}
  	mutex_unlock(&usb_bus_list_lock);
  	return 0;
  
  err_reg:
  	mon_bin_exit();
  err_bin:
  	mon_text_exit();
  err_text:
  	return rc;
  }
  
  static void __exit mon_exit(void)
  {
  	struct mon_bus *mbus;
  	struct list_head *p;
  
  	usb_unregister_notify(&mon_nb);
  	usb_mon_deregister();
  
  	mutex_lock(&mon_lock);
  
  	while (!list_empty(&mon_buses)) {
  		p = mon_buses.next;
  		mbus = list_entry(p, struct mon_bus, bus_link);
  		list_del(p);
  
  		if (mbus->text_inited)
  			mon_text_del(mbus);
  		if (mbus->bin_inited)
  			mon_bin_del(mbus);
  
  		/*
  		 * This never happens, because the open/close paths in
  		 * file level maintain module use counters and so rmmod fails
  		 * before reaching here. However, better be safe...
  		 */
  		if (mbus->nreaders) {
  			printk(KERN_ERR TAG
  			    ": Outstanding opens (%d) on usb%d, leaking...\n",
  			    mbus->nreaders, mbus->u_bus->busnum);
  			atomic_set(&mbus->ref.refcount, 2);	/* Force leak */
  		}
  
  		mon_dissolve(mbus, mbus->u_bus);
  		kref_put(&mbus->ref, mon_bus_drop);
  	}
  
  	mbus = &mon_bus0;
  	if (mbus->text_inited)
  		mon_text_del(mbus);
  	if (mbus->bin_inited)
  		mon_bin_del(mbus);
  
  	mutex_unlock(&mon_lock);
  
  	mon_text_exit();
  	mon_bin_exit();
  }
  
  module_init(mon_init);
  module_exit(mon_exit);
  
  MODULE_LICENSE("GPL");
  