/*
   *  include/linux/eventpoll.h ( Efficent event polling implementation )

   *  Copyright (C) 2001,...,2006	 Davide Libenzi

   *
   *  This program is free software; you can redistribute it and/or modify
   *  it under the terms of the GNU General Public License as published by
   *  the Free Software Foundation; either version 2 of the License, or
   *  (at your option) any later version.
   *
   *  Davide Libenzi <davidel@xmailserver.org>
   *
   */
  
  #ifndef _LINUX_EVENTPOLL_H
  #define _LINUX_EVENTPOLL_H
  
  #include <linux/types.h>
  
  
  /* Valid opcodes to issue to sys_epoll_ctl() */
  #define EPOLL_CTL_ADD 1
  #define EPOLL_CTL_DEL 2
  #define EPOLL_CTL_MOD 3
  
  /* Set the One Shot behaviour for the target file descriptor */
  #define EPOLLONESHOT (1 << 30)
  
  /* Set the Edge Triggered behaviour for the target file descriptor */
  #define EPOLLET (1 << 31)
  
  /* 
   * On x86-64 make the 64bit structure have the same alignment as the
   * 32bit structure. This makes 32bit emulation easier.

   *
   * UML/x86_64 needs the same packing as x86_64 - UML + UML_X86 +
   * 64_BIT adds up to UML/x86_64.

   */
  #ifdef __x86_64__
  #define EPOLL_PACKED __attribute__((packed))
  #else

  #if defined(CONFIG_UML) && defined(CONFIG_UML_X86) && defined(CONFIG_64BIT)
  #define EPOLL_PACKED __attribute__((packed))
  #else

  #define EPOLL_PACKED
  #endif

  #endif

  
  struct epoll_event {
  	__u32 events;
  	__u64 data;
  } EPOLL_PACKED;
  
  #ifdef __KERNEL__
  
  /* Forward declarations to avoid compiler errors */
  struct file;
  
  
  #ifdef CONFIG_EPOLL
  
  /* Used to initialize the epoll bits inside the "struct file" */

  static inline void eventpoll_init_file(struct file *file)
  {
  	INIT_LIST_HEAD(&file->f_ep_links);
  	spin_lock_init(&file->f_ep_lock);
  }

  
  /* Used to release the epoll bits inside the "struct file" */
  void eventpoll_release_file(struct file *file);
  
  /*
   * This is called from inside fs/file_table.c:__fput() to unlink files
   * from the eventpoll interface. We need to have this facility to cleanup
   * correctly files that are closed without being removed from the eventpoll
   * interface.
   */
  static inline void eventpoll_release(struct file *file)
  {
  
  	/*
  	 * Fast check to avoid the get/release of the semaphore. Since
  	 * we're doing this outside the semaphore lock, it might return
  	 * false negatives, but we don't care. It'll help in 99.99% of cases
  	 * to avoid the semaphore lock. False positives simply cannot happen
  	 * because the file in on the way to be removed and nobody ( but
  	 * eventpoll ) has still a reference to this file.
  	 */
  	if (likely(list_empty(&file->f_ep_links)))
  		return;
  
  	/*
  	 * The file is being closed while it is still linked to an epoll
  	 * descriptor. We need to handle this by correctly unlinking it
  	 * from its containers.
  	 */
  	eventpoll_release_file(file);
  }

  #else
  
  static inline void eventpoll_init_file(struct file *file) {}
  static inline void eventpoll_release(struct file *file) {}
  
  #endif
  
  #endif /* #ifdef __KERNEL__ */
  
  #endif /* #ifndef _LINUX_EVENTPOLL_H */