include/linux/notifier.h

   1 /*
   2  *      Routines to manage notifier chains for passing status changes to any
   3  *      interested routines. We need this instead of hard coded call lists so
   4  *      that modules can poke their nose into the innards. The network devices
   5  *      needed them so here they are for the rest of you.
   6  *
   7  *                              Alan Cox <Alan.Cox@linux.org>
   8  */
   9
  10 #ifndef _LINUX_NOTIFIER_H
  11 #define _LINUX_NOTIFIER_H
  12 #include <linux/errno.h>
  13 #include <linux/mutex.h>
  14 #include <linux/rwsem.h>
  15
  16 /*
  17  * Notifier chains are of three types:
  18  *
  19  *      Atomic notifier chains: Chain callbacks run in interrupt/atomic
  20  *              context. Callouts are not allowed to block.
  21  *      Blocking notifier chains: Chain callbacks run in process context.
  22  *              Callouts are allowed to block.
  23  *      Raw notifier chains: There are no restrictions on callbacks,
  24  *              registration, or unregistration.  All locking and protection
  25  *              must be provided by the caller.
  26  *
  27  * atomic_notifier_chain_register() may be called from an atomic context,
  28  * but blocking_notifier_chain_register() must be called from a process
  29  * context.  Ditto for the corresponding _unregister() routines.
  30  *
  31  * atomic_notifier_chain_unregister() and blocking_notifier_chain_unregister()
  32  * _must not_ be called from within the call chain.
  33  */
  34
  35 struct notifier_block {
  36         int (*notifier_call)(struct notifier_block *, unsigned long, void *);
  37         struct notifier_block *next;
  38         int priority;
  39 };
  40
  41 struct atomic_notifier_head {
  42         spinlock_t lock;
  43         struct notifier_block *head;
  44 };
  45
  46 struct blocking_notifier_head {
  47         struct rw_semaphore rwsem;
  48         struct notifier_block *head;
  49 };
  50
  51 struct raw_notifier_head {
  52         struct notifier_block *head;
  53 };
  54
  55 #define ATOMIC_INIT_NOTIFIER_HEAD(name) do {    \
  56                 spin_lock_init(&(name)->lock);  \
  57                 (name)->head = NULL;            \
  58         } while (0)
  59 #define BLOCKING_INIT_NOTIFIER_HEAD(name) do {  \
  60                 init_rwsem(&(name)->rwsem);     \
  61                 (name)->head = NULL;            \
  62         } while (0)
  63 #define RAW_INIT_NOTIFIER_HEAD(name) do {       \
  64                 (name)->head = NULL;            \
  65         } while (0)
  66
  67 #define ATOMIC_NOTIFIER_INIT(name) {                            \
  68                 .lock = __SPIN_LOCK_UNLOCKED(name.lock),        \
  69                 .head = NULL }
  70 #define BLOCKING_NOTIFIER_INIT(name) {                          \
  71                 .rwsem = __RWSEM_INITIALIZER((name).rwsem),     \
  72                 .head = NULL }
  73 #define RAW_NOTIFIER_INIT(name) {                               \
  74                 .head = NULL }
  75
  76 #define ATOMIC_NOTIFIER_HEAD(name)                              \
  77         struct atomic_notifier_head name =                      \
  78                 ATOMIC_NOTIFIER_INIT(name)
  79 #define BLOCKING_NOTIFIER_HEAD(name)                            \
  80         struct blocking_notifier_head name =                    \
  81                 BLOCKING_NOTIFIER_INIT(name)
  82 #define RAW_NOTIFIER_HEAD(name)                                 \
  83         struct raw_notifier_head name =                         \
  84                 RAW_NOTIFIER_INIT(name)
  85
  86 #ifdef __KERNEL__
  87
  88 extern int atomic_notifier_chain_register(struct atomic_notifier_head *,
  89                 struct notifier_block *);
  90 extern int blocking_notifier_chain_register(struct blocking_notifier_head *,
  91                 struct notifier_block *);
  92 extern int raw_notifier_chain_register(struct raw_notifier_head *,
  93                 struct notifier_block *);
  94
  95 extern int atomic_notifier_chain_unregister(struct atomic_notifier_head *,
  96                 struct notifier_block *);
  97 extern int blocking_notifier_chain_unregister(struct blocking_notifier_head *,
  98                 struct notifier_block *);
  99 extern int raw_notifier_chain_unregister(struct raw_notifier_head *,
 100                 struct notifier_block *);
 101
 102 extern int atomic_notifier_call_chain(struct atomic_notifier_head *,
 103                 unsigned long val, void *v);
 104 extern int blocking_notifier_call_chain(struct blocking_notifier_head *,
 105                 unsigned long val, void *v);
 106 extern int raw_notifier_call_chain(struct raw_notifier_head *,
 107                 unsigned long val, void *v);
 108
 109 #define NOTIFY_DONE             0x0000          /* Don't care */
 110 #define NOTIFY_OK               0x0001          /* Suits me */
 111 #define NOTIFY_STOP_MASK        0x8000          /* Don't call further */
 112 #define NOTIFY_BAD              (NOTIFY_STOP_MASK|0x0002)
 113                                                 /* Bad/Veto action */
 114 /*
 115  * Clean way to return from the notifier and stop further calls.
 116  */
 117 #define NOTIFY_STOP             (NOTIFY_OK|NOTIFY_STOP_MASK)
 118
 119 /*
 120  *      Declared notifiers so far. I can imagine quite a few more chains
 121  *      over time (eg laptop power reset chains, reboot chain (to clean
 122  *      device units up), device [un]mount chain, module load/unload chain,
 123  *      low memory chain, screenblank chain (for plug in modular screenblankers)
 124  *      VC switch chains (for loadable kernel svgalib VC switch helpers) etc...
 125  */
 126
 127 /* netdevice notifier chain */
 128 #define NETDEV_UP       0x0001  /* For now you can't veto a device up/down */
 129 #define NETDEV_DOWN     0x0002
 130 #define NETDEV_REBOOT   0x0003  /* Tell a protocol stack a network interface
 131                                    detected a hardware crash and restarted
 132                                    - we can use this eg to kick tcp sessions
 133                                    once done */
 134 #define NETDEV_CHANGE   0x0004  /* Notify device state change */
 135 #define NETDEV_REGISTER 0x0005
 136 #define NETDEV_UNREGISTER       0x0006
 137 #define NETDEV_CHANGEMTU        0x0007
 138 #define NETDEV_CHANGEADDR       0x0008
 139 #define NETDEV_GOING_DOWN       0x0009
 140 #define NETDEV_CHANGENAME       0x000A
 141 #define NETDEV_FEAT_CHANGE      0x000B
 142
 143 #define SYS_DOWN        0x0001  /* Notify of system down */
 144 #define SYS_RESTART     SYS_DOWN
 145 #define SYS_HALT        0x0002  /* Notify of system halt */
 146 #define SYS_POWER_OFF   0x0003  /* Notify of system power off */
 147
 148 #define NETLINK_URELEASE        0x0001  /* Unicast netlink socket released */
 149
 150 #define CPU_ONLINE              0x0002 /* CPU (unsigned)v is up */
 151 #define CPU_UP_PREPARE          0x0003 /* CPU (unsigned)v coming up */
 152 #define CPU_UP_CANCELED         0x0004 /* CPU (unsigned)v NOT coming up */
 153 #define CPU_DOWN_PREPARE        0x0005 /* CPU (unsigned)v going down */
 154 #define CPU_DOWN_FAILED         0x0006 /* CPU (unsigned)v NOT going down */
 155 #define CPU_DEAD                0x0007 /* CPU (unsigned)v dead */
 156
 157 #endif /* __KERNEL__ */
 158 #endif /* _LINUX_NOTIFIER_H */