Release 4.12 include/linux/notifier.h

/*
 *      Routines to manage notifier chains for passing status changes to any
 *      interested routines. We need this instead of hard coded call lists so
 *      that modules can poke their nose into the innards. The network devices
 *      needed them so here they are for the rest of you.
 *
 *                              Alan Cox <Alan.Cox@linux.org>
 */
 
#ifndef _LINUX_NOTIFIER_H

#define _LINUX_NOTIFIER_H
#include <linux/errno.h>
#include <linux/mutex.h>
#include <linux/rwsem.h>
#include <linux/srcu.h>

/*
 * Notifier chains are of four types:
 *
 *      Atomic notifier chains: Chain callbacks run in interrupt/atomic
 *              context. Callouts are not allowed to block.
 *      Blocking notifier chains: Chain callbacks run in process context.
 *              Callouts are allowed to block.
 *      Raw notifier chains: There are no restrictions on callbacks,
 *              registration, or unregistration.  All locking and protection
 *              must be provided by the caller.
 *      SRCU notifier chains: A variant of blocking notifier chains, with
 *              the same restrictions.
 *
 * atomic_notifier_chain_register() may be called from an atomic context,
 * but blocking_notifier_chain_register() and srcu_notifier_chain_register()
 * must be called from a process context.  Ditto for the corresponding
 * _unregister() routines.
 *
 * atomic_notifier_chain_unregister(), blocking_notifier_chain_unregister(),
 * and srcu_notifier_chain_unregister() _must not_ be called from within
 * the call chain.
 *
 * SRCU notifier chains are an alternative form of blocking notifier chains.
 * They use SRCU (Sleepable Read-Copy Update) instead of rw-semaphores for
 * protection of the chain links.  This means there is _very_ low overhead
 * in srcu_notifier_call_chain(): no cache bounces and no memory barriers.
 * As compensation, srcu_notifier_chain_unregister() is rather expensive.
 * SRCU notifier chains should be used when the chain will be called very
 * often but notifier_blocks will seldom be removed.  Also, SRCU notifier
 * chains are slightly more difficult to use because they require special
 * runtime initialization.
 */

struct notifier_block;


typedef	int (*notifier_fn_t)(struct notifier_block *nb,
			unsigned long action, void *data);


struct notifier_block {
	
notifier_fn_t notifier_call;
	
struct notifier_block __rcu *next;
	
int priority;
};


struct atomic_notifier_head {
	
spinlock_t lock;
	
struct notifier_block __rcu *head;
};


struct blocking_notifier_head {
	
struct rw_semaphore rwsem;
	
struct notifier_block __rcu *head;
};


struct raw_notifier_head {
	
struct notifier_block __rcu *head;
};


struct srcu_notifier_head {
	
struct mutex mutex;
	
struct srcu_struct srcu;
	
struct notifier_block __rcu *head;
};


#define ATOMIC_INIT_NOTIFIER_HEAD(name) do {    \
                spin_lock_init(&(name)->lock);  \
                (name)->head = NULL;            \
        } while (0)

#define BLOCKING_INIT_NOTIFIER_HEAD(name) do {    \
                init_rwsem(&(name)->rwsem);     \
                (name)->head = NULL;            \
        } while (0)

#define RAW_INIT_NOTIFIER_HEAD(name) do {    \
                (name)->head = NULL;            \
        } while (0)

/* srcu_notifier_heads must be initialized and cleaned up dynamically */
extern void srcu_init_notifier_head(struct srcu_notifier_head *nh);

#define srcu_cleanup_notifier_head(name)	\
		cleanup_srcu_struct(&(name)->srcu);


#define ATOMIC_NOTIFIER_INIT(name) {                               \
                .lock = __SPIN_LOCK_UNLOCKED(name.lock),        \
                .head = NULL }

#define BLOCKING_NOTIFIER_INIT(name) {                               \
                .rwsem = __RWSEM_INITIALIZER((name).rwsem),     \
                .head = NULL }

#define RAW_NOTIFIER_INIT(name)	{                               \
                .head = NULL }
/* srcu_notifier_heads cannot be initialized statically */


#define ATOMIC_NOTIFIER_HEAD(name)				\
	struct atomic_notifier_head name =                      \
                ATOMIC_NOTIFIER_INIT(name)

#define BLOCKING_NOTIFIER_HEAD(name)				\
	struct blocking_notifier_head name =                    \
                BLOCKING_NOTIFIER_INIT(name)

#define RAW_NOTIFIER_HEAD(name)					\
	struct raw_notifier_head name =                         \
                RAW_NOTIFIER_INIT(name)

#ifdef __KERNEL__

extern int atomic_notifier_chain_register(struct atomic_notifier_head *nh,
		struct notifier_block *nb);
extern int blocking_notifier_chain_register(struct blocking_notifier_head *nh,
		struct notifier_block *nb);
extern int raw_notifier_chain_register(struct raw_notifier_head *nh,
		struct notifier_block *nb);
extern int srcu_notifier_chain_register(struct srcu_notifier_head *nh,
		struct notifier_block *nb);

extern int blocking_notifier_chain_cond_register(
		struct blocking_notifier_head *nh,
		struct notifier_block *nb);

extern int atomic_notifier_chain_unregister(struct atomic_notifier_head *nh,
		struct notifier_block *nb);
extern int blocking_notifier_chain_unregister(struct blocking_notifier_head *nh,
		struct notifier_block *nb);
extern int raw_notifier_chain_unregister(struct raw_notifier_head *nh,
		struct notifier_block *nb);
extern int srcu_notifier_chain_unregister(struct srcu_notifier_head *nh,
		struct notifier_block *nb);

extern int atomic_notifier_call_chain(struct atomic_notifier_head *nh,
		unsigned long val, void *v);
extern int __atomic_notifier_call_chain(struct atomic_notifier_head *nh,
	unsigned long val, void *v, int nr_to_call, int *nr_calls);
extern int blocking_notifier_call_chain(struct blocking_notifier_head *nh,
		unsigned long val, void *v);
extern int __blocking_notifier_call_chain(struct blocking_notifier_head *nh,
	unsigned long val, void *v, int nr_to_call, int *nr_calls);
extern int raw_notifier_call_chain(struct raw_notifier_head *nh,
		unsigned long val, void *v);
extern int __raw_notifier_call_chain(struct raw_notifier_head *nh,
	unsigned long val, void *v, int nr_to_call, int *nr_calls);
extern int srcu_notifier_call_chain(struct srcu_notifier_head *nh,
		unsigned long val, void *v);
extern int __srcu_notifier_call_chain(struct srcu_notifier_head *nh,
	unsigned long val, void *v, int nr_to_call, int *nr_calls);


#define NOTIFY_DONE		0x0000		
/* Don't care */

#define NOTIFY_OK		0x0001		
/* Suits me */

#define NOTIFY_STOP_MASK	0x8000		
/* Don't call further */

#define NOTIFY_BAD		(NOTIFY_STOP_MASK|0x0002)
						/* Bad/Veto action */
/*
 * Clean way to return from the notifier and stop further calls.
 */

#define NOTIFY_STOP		(NOTIFY_OK|NOTIFY_STOP_MASK)

/* Encapsulate (negative) errno value (in particular, NOTIFY_BAD <=> EPERM). */


static inline int notifier_from_errno(int err)
{
	if (err)
		return NOTIFY_STOP_MASK | (NOTIFY_OK - err);

	return NOTIFY_OK;
}

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/* Restore (negative) errno value from notify return value. */


static inline int notifier_to_errno(int ret)
{
	ret &= ~NOTIFY_STOP_MASK;
	return ret > NOTIFY_OK ? NOTIFY_OK - ret : 0;
}

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/*
 *      Declared notifiers so far. I can imagine quite a few more chains
 *      over time (eg laptop power reset chains, reboot chain (to clean 
 *      device units up), device [un]mount chain, module load/unload chain,
 *      low memory chain, screenblank chain (for plug in modular screenblankers) 
 *      VC switch chains (for loadable kernel svgalib VC switch helpers) etc...
 */
 
/* CPU notfiers are defined in include/linux/cpu.h. */

/* netdevice notifiers are defined in include/linux/netdevice.h */

/* reboot notifiers are defined in include/linux/reboot.h. */

/* Hibernation and suspend events are defined in include/linux/suspend.h. */

/* Virtual Terminal events are defined in include/linux/vt.h. */


#define NETLINK_URELEASE	0x0001	
/* Unicast netlink socket released */

/* Console keyboard events.
 * Note: KBD_KEYCODE is always sent before KBD_UNBOUND_KEYCODE, KBD_UNICODE and
 * KBD_KEYSYM. */

#define KBD_KEYCODE		0x0001 
/* Keyboard keycode, called before any other */

#define KBD_UNBOUND_KEYCODE	0x0002 
/* Keyboard keycode which is not bound to any other */

#define KBD_UNICODE		0x0003 
/* Keyboard unicode */

#define KBD_KEYSYM		0x0004 
/* Keyboard keysym */

#define KBD_POST_KEYSYM		0x0005 
/* Called after keyboard keysym interpretation */

extern struct blocking_notifier_head reboot_notifier_list;

#endif /* __KERNEL__ */
#endif /* _LINUX_NOTIFIER_H */
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Herbert Xu
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Andrew Morton
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Directory: include/linux

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