drivers/usb/core/notify.c

   1 /*
   2  * All the USB notify logic
   3  *
   4  * (C) Copyright 2005 Greg Kroah-Hartman <gregkh@suse.de>
   5  *
   6  * notifier functions originally based on those in kernel/sys.c
   7  * but fixed up to not be so broken.
   8  *
   9  */
  10
  11
  12 #include <linux/config.h>
  13 #include <linux/kernel.h>
  14 #include <linux/notifier.h>
  15 #include <linux/usb.h>
  16 #include <linux/mutex.h>
  17 #include "usb.h"
  18
  19
  20 static struct notifier_block *usb_notifier_list;
  21 static DEFINE_MUTEX(usb_notifier_lock);
  22
  23 static void usb_notifier_chain_register(struct notifier_block **list,
  24                                         struct notifier_block *n)
  25 {
  26         mutex_lock(&usb_notifier_lock);
  27         while (*list) {
  28                 if (n->priority > (*list)->priority)
  29                         break;
  30                 list = &((*list)->next);
  31         }
  32         n->next = *list;
  33         *list = n;
  34         mutex_unlock(&usb_notifier_lock);
  35 }
  36
  37 static void usb_notifier_chain_unregister(struct notifier_block **nl,
  38                                    struct notifier_block *n)
  39 {
  40         mutex_lock(&usb_notifier_lock);
  41         while ((*nl)!=NULL) {
  42                 if ((*nl)==n) {
  43                         *nl = n->next;
  44                         goto exit;
  45                 }
  46                 nl=&((*nl)->next);
  47         }
  48 exit:
  49         mutex_unlock(&usb_notifier_lock);
  50 }
  51
  52 static int usb_notifier_call_chain(struct notifier_block **n,
  53                                    unsigned long val, void *v)
  54 {
  55         int ret=NOTIFY_DONE;
  56         struct notifier_block *nb = *n;
  57
  58         mutex_lock(&usb_notifier_lock);
  59         while (nb) {
  60                 ret = nb->notifier_call(nb,val,v);
  61                 if (ret&NOTIFY_STOP_MASK) {
  62                         goto exit;
  63                 }
  64                 nb = nb->next;
  65         }
  66 exit:
  67         mutex_unlock(&usb_notifier_lock);
  68         return ret;
  69 }
  70
  71 /**
  72  * usb_register_notify - register a notifier callback whenever a usb change happens
  73  * @nb: pointer to the notifier block for the callback events.
  74  *
  75  * These changes are either USB devices or busses being added or removed.
  76  */
  77 void usb_register_notify(struct notifier_block *nb)
  78 {
  79         usb_notifier_chain_register(&usb_notifier_list, nb);
  80 }
  81 EXPORT_SYMBOL_GPL(usb_register_notify);
  82
  83 /**
  84  * usb_unregister_notify - unregister a notifier callback
  85  * @nb: pointer to the notifier block for the callback events.
  86  *
  87  * usb_register_notifier() must have been previously called for this function
  88  * to work properly.
  89  */
  90 void usb_unregister_notify(struct notifier_block *nb)
  91 {
  92         usb_notifier_chain_unregister(&usb_notifier_list, nb);
  93 }
  94 EXPORT_SYMBOL_GPL(usb_unregister_notify);
  95
  96
  97 void usb_notify_add_device(struct usb_device *udev)
  98 {
  99         usb_notifier_call_chain(&usb_notifier_list, USB_DEVICE_ADD, udev);
 100 }
 101
 102 void usb_notify_remove_device(struct usb_device *udev)
 103 {
 104         usb_notifier_call_chain(&usb_notifier_list, USB_DEVICE_REMOVE, udev);
 105 }
 106
 107 void usb_notify_add_bus(struct usb_bus *ubus)
 108 {
 109         usb_notifier_call_chain(&usb_notifier_list, USB_BUS_ADD, ubus);
 110 }
 111
 112 void usb_notify_remove_bus(struct usb_bus *ubus)
 113 {
 114         usb_notifier_call_chain(&usb_notifier_list, USB_BUS_REMOVE, ubus);
 115 }