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/*

 * 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 */

        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 */

        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 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 */