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 "usb.h"
  17
  18
  19 static struct notifier_block *usb_notifier_list;
  20 static DECLARE_MUTEX(usb_notifier_lock);
  21
  22 static void usb_notifier_chain_register(struct notifier_block **list,
  23                                         struct notifier_block *n)
  24 {
  25         down(&usb_notifier_lock);
  26         while (*list) {
  27                 if (n->priority > (*list)->priority)
  28                         break;
  29                 list = &((*list)->next);
  30         }
  31         n->next = *list;
  32         *list = n;
  33         up(&usb_notifier_lock);
  34 }
  35
  36 static void usb_notifier_chain_unregister(struct notifier_block **nl,
  37                                    struct notifier_block *n)
  38 {
  39         down(&usb_notifier_lock);
  40         while ((*nl)!=NULL) {
  41                 if ((*nl)==n) {
  42                         *nl = n->next;
  43                         goto exit;
  44                 }
  45                 nl=&((*nl)->next);
  46         }
  47 exit:
  48         up(&usb_notifier_lock);
  49 }
  50
  51 static int usb_notifier_call_chain(struct notifier_block **n,
  52                                    unsigned long val, void *v)
  53 {
  54         int ret=NOTIFY_DONE;
  55         struct notifier_block *nb = *n;
  56
  57         down(&usb_notifier_lock);
  58         while (nb) {
  59                 ret = nb->notifier_call(nb,val,v);
  60                 if (ret&NOTIFY_STOP_MASK) {
  61                         goto exit;
  62                 }
  63                 nb = nb->next;
  64         }
  65 exit:
  66         up(&usb_notifier_lock);
  67         return ret;
  68 }
  69
  70 /**
  71  * usb_register_notify - register a notifier callback whenever a usb change happens
  72  * @nb: pointer to the notifier block for the callback events.
  73  *
  74  * These changes are either USB devices or busses being added or removed.
  75  */
  76 void usb_register_notify(struct notifier_block *nb)
  77 {
  78         usb_notifier_chain_register(&usb_notifier_list, nb);
  79 }
  80 EXPORT_SYMBOL_GPL(usb_register_notify);
  81
  82 /**
  83  * usb_unregister_notify - unregister a notifier callback
  84  * @nb: pointer to the notifier block for the callback events.
  85  *
  86  * usb_register_notifier() must have been previously called for this function
  87  * to work properly.
  88  */
  89 void usb_unregister_notify(struct notifier_block *nb)
  90 {
  91         usb_notifier_chain_unregister(&usb_notifier_list, nb);
  92 }
  93 EXPORT_SYMBOL_GPL(usb_unregister_notify);
  94
  95
  96 void usb_notify_add_device(struct usb_device *udev)
  97 {
  98         usb_notifier_call_chain(&usb_notifier_list, USB_DEVICE_ADD, udev);
  99 }
 100
 101 void usb_notify_remove_device(struct usb_device *udev)
 102 {
 103         usb_notifier_call_chain(&usb_notifier_list, USB_DEVICE_REMOVE, udev);
 104 }
 105
 106 void usb_notify_add_bus(struct usb_bus *ubus)
 107 {
 108         usb_notifier_call_chain(&usb_notifier_list, USB_BUS_ADD, ubus);
 109 }
 110
 111 void usb_notify_remove_bus(struct usb_bus *ubus)
 112 {
 113         usb_notifier_call_chain(&usb_notifier_list, USB_BUS_REMOVE, ubus);
 114 }