#ifndef _LINUX_RING_BUFFER_H
  #define _LINUX_RING_BUFFER_H

  #include <linux/kmemcheck.h>

  #include <linux/mm.h>
  #include <linux/seq_file.h>

  #include <linux/poll.h>

  
  struct ring_buffer;
  struct ring_buffer_iter;
  
  /*

   * Don't refer to this struct directly, use functions below.

   */
  struct ring_buffer_event {

  	kmemcheck_bitfield_begin(bitfield);

  	u32		type_len:5, time_delta:27;

  	kmemcheck_bitfield_end(bitfield);

  	u32		array[];
  };
  
  /**
   * enum ring_buffer_type - internal ring buffer types
   *

   * @RINGBUF_TYPE_PADDING:	Left over page padding or discarded event
   *				 If time_delta is 0:
   *				  array is ignored
   *				  size is variable depending on how much

   *				  padding is needed

   *				 If time_delta is non zero:

   *				  array[0] holds the actual length
   *				  size = 4 + length (bytes)

   *
   * @RINGBUF_TYPE_TIME_EXTEND:	Extend the time delta
   *				 array[0] = time delta (28 .. 59)
   *				 size = 8 bytes
   *
   * @RINGBUF_TYPE_TIME_STAMP:	Sync time stamp with external clock

   *				 array[0]    = tv_nsec
   *				 array[1..2] = tv_sec

   *				 size = 16 bytes
   *

   * <= @RINGBUF_TYPE_DATA_TYPE_LEN_MAX:
   *				Data record
   *				 If type_len is zero:

   *				  array[0] holds the actual length

   *				  array[1..(length+3)/4] holds data

   *				  size = 4 + length (bytes)

   *				 else

   *				  length = type_len << 2

   *				  array[0..(length+3)/4-1] holds data
   *				  size = 4 + length (bytes)

   */
  enum ring_buffer_type {

  	RINGBUF_TYPE_DATA_TYPE_LEN_MAX = 28,

  	RINGBUF_TYPE_PADDING,
  	RINGBUF_TYPE_TIME_EXTEND,
  	/* FIXME: RINGBUF_TYPE_TIME_STAMP not implemented */
  	RINGBUF_TYPE_TIME_STAMP,

  };
  
  unsigned ring_buffer_event_length(struct ring_buffer_event *event);
  void *ring_buffer_event_data(struct ring_buffer_event *event);

  /*

   * ring_buffer_discard_commit will remove an event that has not
   *   ben committed yet. If this is used, then ring_buffer_unlock_commit
   *   must not be called on the discarded event. This function
   *   will try to remove the event from the ring buffer completely
   *   if another event has not been written after it.
   *
   * Example use:
   *
   *  if (some_condition)
   *    ring_buffer_discard_commit(buffer, event);
   *  else
   *    ring_buffer_unlock_commit(buffer, event);
   */
  void ring_buffer_discard_commit(struct ring_buffer *buffer,
  				struct ring_buffer_event *event);
  
  /*

   * size is in bytes for each per CPU buffer.
   */
  struct ring_buffer *

  __ring_buffer_alloc(unsigned long size, unsigned flags, struct lock_class_key *key);
  
  /*
   * Because the ring buffer is generic, if other users of the ring buffer get
   * traced by ftrace, it can produce lockdep warnings. We need to keep each
   * ring buffer's lock class separate.
   */
  #define ring_buffer_alloc(size, flags)			\
  ({							\
  	static struct lock_class_key __key;		\
  	__ring_buffer_alloc((size), (flags), &__key);	\
  })

  int ring_buffer_wait(struct ring_buffer *buffer, int cpu, bool full);

  int ring_buffer_poll_wait(struct ring_buffer *buffer, int cpu,
  			  struct file *filp, poll_table *poll_table);

  #define RING_BUFFER_ALL_CPUS -1

  void ring_buffer_free(struct ring_buffer *buffer);

  int ring_buffer_resize(struct ring_buffer *buffer, unsigned long size, int cpu);

  void ring_buffer_change_overwrite(struct ring_buffer *buffer, int val);

  struct ring_buffer_event *ring_buffer_lock_reserve(struct ring_buffer *buffer,
  						   unsigned long length);

  int ring_buffer_unlock_commit(struct ring_buffer *buffer,

  			      struct ring_buffer_event *event);

  int ring_buffer_write(struct ring_buffer *buffer,
  		      unsigned long length, void *data);
  
  struct ring_buffer_event *

  ring_buffer_peek(struct ring_buffer *buffer, int cpu, u64 *ts,
  		 unsigned long *lost_events);

  struct ring_buffer_event *

  ring_buffer_consume(struct ring_buffer *buffer, int cpu, u64 *ts,
  		    unsigned long *lost_events);

  
  struct ring_buffer_iter *

  ring_buffer_read_prepare(struct ring_buffer *buffer, int cpu);
  void ring_buffer_read_prepare_sync(void);
  void ring_buffer_read_start(struct ring_buffer_iter *iter);

  void ring_buffer_read_finish(struct ring_buffer_iter *iter);
  
  struct ring_buffer_event *
  ring_buffer_iter_peek(struct ring_buffer_iter *iter, u64 *ts);
  struct ring_buffer_event *
  ring_buffer_read(struct ring_buffer_iter *iter, u64 *ts);
  void ring_buffer_iter_reset(struct ring_buffer_iter *iter);
  int ring_buffer_iter_empty(struct ring_buffer_iter *iter);

  unsigned long ring_buffer_size(struct ring_buffer *buffer, int cpu);

  
  void ring_buffer_reset_cpu(struct ring_buffer *buffer, int cpu);
  void ring_buffer_reset(struct ring_buffer *buffer);

  #ifdef CONFIG_RING_BUFFER_ALLOW_SWAP

  int ring_buffer_swap_cpu(struct ring_buffer *buffer_a,
  			 struct ring_buffer *buffer_b, int cpu);

  #else
  static inline int
  ring_buffer_swap_cpu(struct ring_buffer *buffer_a,
  		     struct ring_buffer *buffer_b, int cpu)
  {
  	return -ENODEV;
  }
  #endif

  bool ring_buffer_empty(struct ring_buffer *buffer);
  bool ring_buffer_empty_cpu(struct ring_buffer *buffer, int cpu);

  
  void ring_buffer_record_disable(struct ring_buffer *buffer);
  void ring_buffer_record_enable(struct ring_buffer *buffer);

  void ring_buffer_record_off(struct ring_buffer *buffer);
  void ring_buffer_record_on(struct ring_buffer *buffer);
  int ring_buffer_record_is_on(struct ring_buffer *buffer);

  void ring_buffer_record_disable_cpu(struct ring_buffer *buffer, int cpu);
  void ring_buffer_record_enable_cpu(struct ring_buffer *buffer, int cpu);

  u64 ring_buffer_oldest_event_ts(struct ring_buffer *buffer, int cpu);

  unsigned long ring_buffer_bytes_cpu(struct ring_buffer *buffer, int cpu);

  unsigned long ring_buffer_entries(struct ring_buffer *buffer);
  unsigned long ring_buffer_overruns(struct ring_buffer *buffer);

  unsigned long ring_buffer_entries_cpu(struct ring_buffer *buffer, int cpu);
  unsigned long ring_buffer_overrun_cpu(struct ring_buffer *buffer, int cpu);

  unsigned long ring_buffer_commit_overrun_cpu(struct ring_buffer *buffer, int cpu);

  unsigned long ring_buffer_dropped_events_cpu(struct ring_buffer *buffer, int cpu);

  unsigned long ring_buffer_read_events_cpu(struct ring_buffer *buffer, int cpu);

  u64 ring_buffer_time_stamp(struct ring_buffer *buffer, int cpu);
  void ring_buffer_normalize_time_stamp(struct ring_buffer *buffer,
  				      int cpu, u64 *ts);
  void ring_buffer_set_clock(struct ring_buffer *buffer,
  			   u64 (*clock)(void));

  size_t ring_buffer_page_len(void *page);

  void *ring_buffer_alloc_read_page(struct ring_buffer *buffer, int cpu);

  void ring_buffer_free_read_page(struct ring_buffer *buffer, void *data);

  int ring_buffer_read_page(struct ring_buffer *buffer, void **data_page,
  			  size_t len, int cpu, int full);

  struct trace_seq;
  
  int ring_buffer_print_entry_header(struct trace_seq *s);
  int ring_buffer_print_page_header(struct trace_seq *s);

  enum ring_buffer_flags {
  	RB_FL_OVERWRITE		= 1 << 0,
  };
  
  #endif /* _LINUX_RING_BUFFER_H */