/*

 * linux/include/linux/relay.h

 *

 * Copyright (C) 2002, 2003 - Tom Zanussi (zanussi@us.ibm.com), IBM Corp

 * Copyright (C) 1999, 2000, 2001, 2002 - Karim Yaghmour (karim@opersys.com)

 *

 * CONFIG_RELAY definitions and declarations

 */

#ifndef _LINUX_RELAY_H

#define _LINUX_RELAY_H

#include <linux/types.h>

#include <linux/sched.h>

#include <linux/timer.h>

#include <linux/wait.h>

#include <linux/list.h>

#include <linux/fs.h>

#include <linux/poll.h>

#include <linux/kref.h>

/* Needs a _much_ better name... */

#define FIX_SIZE(x) ((((x) - 1) & PAGE_MASK) + PAGE_SIZE)

/*

 * Tracks changes to rchan/rchan_buf structs

 */

#define RELAYFS_CHANNEL_VERSION		7

/*

 * Per-cpu relay channel buffer

 */

struct rchan_buf

{

	void *start;			/* start of channel buffer */

	void *data;			/* start of current sub-buffer */

	size_t offset;			/* current offset into sub-buffer */

	size_t subbufs_produced;	/* count of sub-buffers produced */

	size_t subbufs_consumed;	/* count of sub-buffers consumed */

	struct rchan *chan;		/* associated channel */

	wait_queue_head_t read_wait;	/* reader wait queue */

	struct timer_list timer; 	/* reader wake-up timer */

	struct dentry *dentry;		/* channel file dentry */

	struct kref kref;		/* channel buffer refcount */

	struct page **page_array;	/* array of current buffer pages */

	unsigned int page_count;	/* number of current buffer pages */

	unsigned int finalized;		/* buffer has been finalized */

	size_t *padding;		/* padding counts per sub-buffer */

	size_t prev_padding;		/* temporary variable */

	size_t bytes_consumed;		/* bytes consumed in cur read subbuf */

	size_t early_bytes;		/* bytes consumed before VFS inited */

	unsigned int cpu;		/* this buf's cpu */

} ____cacheline_aligned;

/*

 * Relay channel data structure

 */

struct rchan

{

	u32 version;			/* the version of this struct */

	size_t subbuf_size;		/* sub-buffer size */

	size_t n_subbufs;		/* number of sub-buffers per buffer */

	size_t alloc_size;		/* total buffer size allocated */

	struct rchan_callbacks *cb;	/* client callbacks */

	struct kref kref;		/* channel refcount */

	void *private_data;		/* for user-defined data */

	size_t last_toobig;		/* tried to log event > subbuf size */

	struct rchan_buf *buf[NR_CPUS]; /* per-cpu channel buffers */

	int is_global;			/* One global buffer ? */

	struct list_head list;		/* for channel list */

	struct dentry *parent;		/* parent dentry passed to open */

	int has_base_filename;		/* has a filename associated? */

	char base_filename[NAME_MAX];	/* saved base filename */

};

/*

 * Relay channel client callbacks

 */

struct rchan_callbacks

{

	/*

	 * subbuf_start - called on buffer-switch to a new sub-buffer

	 * @buf: the channel buffer containing the new sub-buffer

	 * @subbuf: the start of the new sub-buffer

	 * @prev_subbuf: the start of the previous sub-buffer

	 * @prev_padding: unused space at the end of previous sub-buffer

	 *

	 * The client should return 1 to continue logging, 0 to stop

	 * logging.

	 *

	 * NOTE: subbuf_start will also be invoked when the buffer is

	 *       created, so that the first sub-buffer can be initialized

	 *       if necessary.  In this case, prev_subbuf will be NULL.

	 *

	 * NOTE: the client can reserve bytes at the beginning of the new

	 *       sub-buffer by calling subbuf_start_reserve() in this callback.

	 */

	int (*subbuf_start) (struct rchan_buf *buf,

			     void *subbuf,

			     void *prev_subbuf,

			     size_t prev_padding);

	/*

	 * buf_mapped - relay buffer mmap notification

	 * @buf: the channel buffer

	 * @filp: relay file pointer

	 *

	 * Called when a relay file is successfully mmapped

	 */

        void (*buf_mapped)(struct rchan_buf *buf,

			   struct file *filp);

	/*

	 * buf_unmapped - relay buffer unmap notification

	 * @buf: the channel buffer

	 * @filp: relay file pointer

	 *

	 * Called when a relay file is successfully unmapped

	 */

        void (*buf_unmapped)(struct rchan_buf *buf,

			     struct file *filp);

	/*

	 * create_buf_file - create file to represent a relay channel buffer

	 * @filename: the name of the file to create

	 * @parent: the parent of the file to create

	 * @mode: the mode of the file to create

	 * @buf: the channel buffer

	 * @is_global: outparam - set non-zero if the buffer should be global

	 *

	 * Called during relay_open(), once for each per-cpu buffer,

	 * to allow the client to create a file to be used to

	 * represent the corresponding channel buffer.  If the file is

	 * created outside of relay, the parent must also exist in

	 * that filesystem.

	 *

	 * The callback should return the dentry of the file created

	 * to represent the relay buffer.

	 *

	 * Setting the is_global outparam to a non-zero value will

	 * cause relay_open() to create a single global buffer rather

	 * than the default set of per-cpu buffers.

	 *

	 * See Documentation/filesystems/relayfs.txt for more info.

	 */

	struct dentry *(*create_buf_file)(const char *filename,

					  struct dentry *parent,

					  int mode,

					  struct rchan_buf *buf,

					  int *is_global);

	/*

	 * remove_buf_file - remove file representing a relay channel buffer

	 * @dentry: the dentry of the file to remove

	 *

	 * Called during relay_close(), once for each per-cpu buffer,

	 * to allow the client to remove a file used to represent a

	 * channel buffer.

	 *

	 * The callback should return 0 if successful, negative if not.

	 */

	int (*remove_buf_file)(struct dentry *dentry);

};

/*

 * CONFIG_RELAY kernel API, kernel/relay.c

 */

struct rchan *relay_open(const char *base_filename,

			 struct dentry *parent,

			 size_t subbuf_size,

			 size_t n_subbufs,

			 struct rchan_callbacks *cb,

			 void *private_data);

extern int relay_late_setup_files(struct rchan *chan,

				  const char *base_filename,

				  struct dentry *parent);

extern void relay_close(struct rchan *chan);

extern void relay_flush(struct rchan *chan);

extern void relay_subbufs_consumed(struct rchan *chan,

				   unsigned int cpu,

				   size_t consumed);

extern void relay_reset(struct rchan *chan);

extern int relay_buf_full(struct rchan_buf *buf);

extern size_t relay_switch_subbuf(struct rchan_buf *buf,

				  size_t length);

/**

 *	relay_write - write data into the channel

 *	@chan: relay channel

 *	@data: data to be written

 *	@length: number of bytes to write

 *

 *	Writes data into the current cpu's channel buffer.

 *

 *	Protects the buffer by disabling interrupts.  Use this

 *	if you might be logging from interrupt context.  Try

 *	__relay_write() if you know you	won't be logging from

 *	interrupt context.

 */

static inline void relay_write(struct rchan *chan,

			       const void *data,

			       size_t length)

{

	unsigned long flags;

	struct rchan_buf *buf;

	local_irq_save(flags);

	buf = chan->buf[smp_processor_id()];

	if (unlikely(buf->offset + length > chan->subbuf_size))

		length = relay_switch_subbuf(buf, length);

	memcpy(buf->data + buf->offset, data, length);

	buf->offset += length;

	local_irq_restore(flags);

}

/**

 *	__relay_write - write data into the channel

 *	@chan: relay channel

 *	@data: data to be written

 *	@length: number of bytes to write

 *

 *	Writes data into the current cpu's channel buffer.

 *

 *	Protects the buffer by disabling preemption.  Use

 *	relay_write() if you might be logging from interrupt

 *	context.

 */

static inline void __relay_write(struct rchan *chan,

				 const void *data,

				 size_t length)

{

	struct rchan_buf *buf;

	buf = chan->buf[get_cpu()];

	if (unlikely(buf->offset + length > buf->chan->subbuf_size))

		length = relay_switch_subbuf(buf, length);

	memcpy(buf->data + buf->offset, data, length);

	buf->offset += length;

	put_cpu();

}

/**

 *	relay_reserve - reserve slot in channel buffer

 *	@chan: relay channel

 *	@length: number of bytes to reserve

 *

 *	Returns pointer to reserved slot, NULL if full.

 *

 *	Reserves a slot in the current cpu's channel buffer.

 *	Does not protect the buffer at all - caller must provide

 *	appropriate synchronization.

 */

static inline void *relay_reserve(struct rchan *chan, size_t length)

{

	void *reserved;

	struct rchan_buf *buf = chan->buf[smp_processor_id()];

	if (unlikely(buf->offset + length > buf->chan->subbuf_size)) {

		length = relay_switch_subbuf(buf, length);

		if (!length)

			return NULL;

	}

	reserved = buf->data + buf->offset;

	buf->offset += length;

	return reserved;

}

/**

 *	subbuf_start_reserve - reserve bytes at the start of a sub-buffer

 *	@buf: relay channel buffer

 *	@length: number of bytes to reserve

 *

 *	Helper function used to reserve bytes at the beginning of

 *	a sub-buffer in the subbuf_start() callback.

 */

static inline void subbuf_start_reserve(struct rchan_buf *buf,

					size_t length)

{

	BUG_ON(length >= buf->chan->subbuf_size - 1);

	buf->offset = length;

}

/*

 * exported relay file operations, kernel/relay.c

 */

extern const struct file_operations relay_file_operations;

#endif /* _LINUX_RELAY_H */