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70 lines
2.7 KiB
C
70 lines
2.7 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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/*
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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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typedef int (*notifier_fn_t)(struct notifier_block *nb,
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unsigned long action, void *data);
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struct notifier_block {
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notifier_fn_t notifier_call;
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struct notifier_block __rcu *next;
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int priority;
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};
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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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#endif /* _LINUX_NOTIFIER_H */
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