213 lines
7.6 KiB
C
213 lines
7.6 KiB
C
/*
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* Routines to manage notifier chains for passing status changes to any
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* interested routines. We need this instead of hard coded call lists so
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* that modules can poke their nose into the innards. The network devices
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* needed them so here they are for the rest of you.
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*
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* Alan Cox <Alan.Cox@linux.org>
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*/
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#ifndef _LINUX_NOTIFIER_H
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#define _LINUX_NOTIFIER_H
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#include <linux/errno.h>
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#include <linux/mutex.h>
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#include <linux/rwsem.h>
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#include <linux/srcu.h>
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/*
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* Notifier chains are of four types:
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*
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* Atomic notifier chains: Chain callbacks run in interrupt/atomic
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* context. Callouts are not allowed to block.
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* Blocking notifier chains: Chain callbacks run in process context.
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* Callouts are allowed to block.
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* Raw notifier chains: There are no restrictions on callbacks,
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* registration, or unregistration. All locking and protection
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* must be provided by the caller.
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* SRCU notifier chains: A variant of blocking notifier chains, with
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* the same restrictions.
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*
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* atomic_notifier_chain_register() may be called from an atomic context,
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* but blocking_notifier_chain_register() and srcu_notifier_chain_register()
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* must be called from a process context. Ditto for the corresponding
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* _unregister() routines.
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*
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* atomic_notifier_chain_unregister(), blocking_notifier_chain_unregister(),
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* and srcu_notifier_chain_unregister() _must not_ be called from within
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* the call chain.
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*
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* SRCU notifier chains are an alternative form of blocking notifier chains.
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* They use SRCU (Sleepable Read-Copy Update) instead of rw-semaphores for
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* protection of the chain links. This means there is _very_ low overhead
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* in srcu_notifier_call_chain(): no cache bounces and no memory barriers.
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* As compensation, srcu_notifier_chain_unregister() is rather expensive.
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* SRCU notifier chains should be used when the chain will be called very
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* often but notifier_blocks will seldom be removed. Also, SRCU notifier
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* chains are slightly more difficult to use because they require special
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* runtime initialization.
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*/
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struct notifier_block {
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int (*notifier_call)(struct notifier_block *, unsigned long, void *);
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struct notifier_block __rcu *next;
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int priority;
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};
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struct atomic_notifier_head {
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spinlock_t lock;
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struct notifier_block __rcu *head;
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};
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struct blocking_notifier_head {
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struct rw_semaphore rwsem;
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struct notifier_block __rcu *head;
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};
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struct raw_notifier_head {
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struct notifier_block __rcu *head;
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};
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struct srcu_notifier_head {
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struct mutex mutex;
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struct srcu_struct srcu;
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struct notifier_block __rcu *head;
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};
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#define ATOMIC_INIT_NOTIFIER_HEAD(name) do { \
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spin_lock_init(&(name)->lock); \
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(name)->head = NULL; \
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} while (0)
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#define BLOCKING_INIT_NOTIFIER_HEAD(name) do { \
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init_rwsem(&(name)->rwsem); \
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(name)->head = NULL; \
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} while (0)
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#define RAW_INIT_NOTIFIER_HEAD(name) do { \
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(name)->head = NULL; \
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} while (0)
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/* srcu_notifier_heads must be initialized and cleaned up dynamically */
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extern void srcu_init_notifier_head(struct srcu_notifier_head *nh);
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#define srcu_cleanup_notifier_head(name) \
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cleanup_srcu_struct(&(name)->srcu);
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#define ATOMIC_NOTIFIER_INIT(name) { \
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.lock = __SPIN_LOCK_UNLOCKED(name.lock), \
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.head = NULL }
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#define BLOCKING_NOTIFIER_INIT(name) { \
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.rwsem = __RWSEM_INITIALIZER((name).rwsem), \
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.head = NULL }
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#define RAW_NOTIFIER_INIT(name) { \
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.head = NULL }
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/* srcu_notifier_heads cannot be initialized statically */
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#define ATOMIC_NOTIFIER_HEAD(name) \
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struct atomic_notifier_head name = \
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ATOMIC_NOTIFIER_INIT(name)
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#define BLOCKING_NOTIFIER_HEAD(name) \
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struct blocking_notifier_head name = \
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BLOCKING_NOTIFIER_INIT(name)
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#define RAW_NOTIFIER_HEAD(name) \
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struct raw_notifier_head name = \
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RAW_NOTIFIER_INIT(name)
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#ifdef __KERNEL__
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extern int atomic_notifier_chain_register(struct atomic_notifier_head *nh,
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struct notifier_block *nb);
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extern int blocking_notifier_chain_register(struct blocking_notifier_head *nh,
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struct notifier_block *nb);
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extern int raw_notifier_chain_register(struct raw_notifier_head *nh,
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struct notifier_block *nb);
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extern int srcu_notifier_chain_register(struct srcu_notifier_head *nh,
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struct notifier_block *nb);
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extern int blocking_notifier_chain_cond_register(
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struct blocking_notifier_head *nh,
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struct notifier_block *nb);
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extern int atomic_notifier_chain_unregister(struct atomic_notifier_head *nh,
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struct notifier_block *nb);
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extern int blocking_notifier_chain_unregister(struct blocking_notifier_head *nh,
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struct notifier_block *nb);
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extern int raw_notifier_chain_unregister(struct raw_notifier_head *nh,
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struct notifier_block *nb);
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extern int srcu_notifier_chain_unregister(struct srcu_notifier_head *nh,
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struct notifier_block *nb);
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extern int atomic_notifier_call_chain(struct atomic_notifier_head *nh,
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unsigned long val, void *v);
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extern int __atomic_notifier_call_chain(struct atomic_notifier_head *nh,
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unsigned long val, void *v, int nr_to_call, int *nr_calls);
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extern int blocking_notifier_call_chain(struct blocking_notifier_head *nh,
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unsigned long val, void *v);
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extern int __blocking_notifier_call_chain(struct blocking_notifier_head *nh,
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unsigned long val, void *v, int nr_to_call, int *nr_calls);
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extern int raw_notifier_call_chain(struct raw_notifier_head *nh,
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unsigned long val, void *v);
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extern int __raw_notifier_call_chain(struct raw_notifier_head *nh,
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unsigned long val, void *v, int nr_to_call, int *nr_calls);
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extern int srcu_notifier_call_chain(struct srcu_notifier_head *nh,
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unsigned long val, void *v);
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extern int __srcu_notifier_call_chain(struct srcu_notifier_head *nh,
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unsigned long val, void *v, int nr_to_call, int *nr_calls);
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#define NOTIFY_DONE 0x0000 /* Don't care */
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#define NOTIFY_OK 0x0001 /* Suits me */
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#define NOTIFY_STOP_MASK 0x8000 /* Don't call further */
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#define NOTIFY_BAD (NOTIFY_STOP_MASK|0x0002)
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/* Bad/Veto action */
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/*
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* Clean way to return from the notifier and stop further calls.
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*/
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#define NOTIFY_STOP (NOTIFY_OK|NOTIFY_STOP_MASK)
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/* Encapsulate (negative) errno value (in particular, NOTIFY_BAD <=> EPERM). */
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static inline int notifier_from_errno(int err)
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{
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if (err)
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return NOTIFY_STOP_MASK | (NOTIFY_OK - err);
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return NOTIFY_OK;
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}
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/* Restore (negative) errno value from notify return value. */
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static inline int notifier_to_errno(int ret)
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{
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ret &= ~NOTIFY_STOP_MASK;
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return ret > NOTIFY_OK ? NOTIFY_OK - ret : 0;
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}
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/*
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* Declared notifiers so far. I can imagine quite a few more chains
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* over time (eg laptop power reset chains, reboot chain (to clean
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* device units up), device [un]mount chain, module load/unload chain,
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* low memory chain, screenblank chain (for plug in modular screenblankers)
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* VC switch chains (for loadable kernel svgalib VC switch helpers) etc...
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*/
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/* CPU notfiers are defined in include/linux/cpu.h. */
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/* netdevice notifiers are defined in include/linux/netdevice.h */
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/* reboot notifiers are defined in include/linux/reboot.h. */
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/* Hibernation and suspend events are defined in include/linux/suspend.h. */
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/* Virtual Terminal events are defined in include/linux/vt.h. */
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#define NETLINK_URELEASE 0x0001 /* Unicast netlink socket released */
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/* Console keyboard events.
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* Note: KBD_KEYCODE is always sent before KBD_UNBOUND_KEYCODE, KBD_UNICODE and
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* KBD_KEYSYM. */
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#define KBD_KEYCODE 0x0001 /* Keyboard keycode, called before any other */
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#define KBD_UNBOUND_KEYCODE 0x0002 /* Keyboard keycode which is not bound to any other */
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#define KBD_UNICODE 0x0003 /* Keyboard unicode */
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#define KBD_KEYSYM 0x0004 /* Keyboard keysym */
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#define KBD_POST_KEYSYM 0x0005 /* Called after keyboard keysym interpretation */
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extern struct blocking_notifier_head reboot_notifier_list;
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#endif /* __KERNEL__ */
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#endif /* _LINUX_NOTIFIER_H */
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