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/** \file
 * IO channel
 */

#ifndef SPDK_IO_CHANNEL_H_
#define SPDK_IO_CHANNEL_H_

#include "spdk/stdinc.h"

#include "spdk/queue.h"

struct spdk_thread;
struct spdk_io_channel;

typedef void (*spdk_thread_fn)(void *ctx);
typedef void (*spdk_thread_pass_msg)(spdk_thread_fn fn, void *ctx,
				     void *thread_ctx);

typedef int (*io_channel_create_cb_t)(void *io_device, void *ctx_buf);
typedef void (*io_channel_destroy_cb_t)(void *io_device, void *ctx_buf);

/**
 * \brief Initializes the calling thread for I/O channel allocation.
 *
 * @param fn A function that may be called from any thread and is
 *          passed a function pointer (spdk_thread_fn) that must be
 *          called on the same thread that spdk_allocate_thread
 *          was called from.
 * @param thread_ctx Context that will be passed to fn.
 */
struct spdk_thread *spdk_allocate_thread(spdk_thread_pass_msg fn, void *thread_ctx);

/**
 * \brief Releases any resources related to the calling thread for I/O channel allocation.
 *
 * All I/O channel references related to the calling thread must be released using
 *  spdk_put_io_channel() prior to calling this function.
 */
void spdk_free_thread(void);

/**
 * \brief Get a handle to the current thread. This handle may be passed
 * to other threads and used as the target of spdk_thread_send_msg().
 */
struct spdk_thread *spdk_get_thread(void);

/**
 * \brief Send a message to the given thread. The message
 * may be sent asynchronously - i.e. spdk_thread_send_msg
 * may return prior to `fn` being called.
 *
 * @param thread The target thread.
 * @param fn This function will be called on the given thread.
 * @param ctx This context will be passed to fn when called.
 */
void spdk_thread_send_msg(const struct spdk_thread *thread, spdk_thread_fn fn, void *ctx);

/**
 * \brief Register the opaque io_device context as an I/O device.
 *
 * After an I/O device is registered, it can return I/O channels using the
 *  spdk_get_io_channel() function.  create_cb is the callback function invoked
 *  to allocate any resources required for a new I/O channel.  destroy_cb is the
 *  callback function invoked to release the resources for an I/O channel.  ctx_size
 *  is the size of the context buffer allocated to store references to allocated I/O
 *  channel resources.
 */
void spdk_io_device_register(void *io_device, io_channel_create_cb_t create_cb,
			     io_channel_destroy_cb_t destroy_cb, uint32_t ctx_size);

/**
 * \brief Unregister the opaque io_device context as an I/O device.
 *
 * Callers must ensure they release references to any I/O channel related to this
 *  device before calling this function.
 */
void spdk_io_device_unregister(void *io_device);

/**
 * \brief Gets an I/O channel for the specified io_device to be used by the calling thread.
 *
 * The io_device context pointer specified must have previously been registered using
 *  spdk_io_device_register().  If an existing I/O channel does not exist yet for the given
 *  io_device on the calling thread, it will allocate an I/O channel and invoke the create_cb
 *  function pointer specified in spdk_io_device_register().  If an I/O channel already
 *  exists for the given io_device on the calling thread, its reference is returned rather
 *  than creating a new I/O channel.
 */
struct spdk_io_channel *spdk_get_io_channel(void *io_device);

/**
 * \brief Releases a reference to an I/O channel.
 *
 * Must be called from the same thread that called spdk_get_io_channel() for the specified
 *  I/O channel.  If this releases the last reference to the I/O channel, The destroy_cb
 *  function specified in spdk_io_device_register() will be invoked to release any
 *  associated resources.
 */
void spdk_put_io_channel(struct spdk_io_channel *ch);

/**
 * \brief Returns the context buffer associated with an I/O channel.
 */
void *spdk_io_channel_get_ctx(struct spdk_io_channel *ch);

#endif /* SPDK_IO_CHANNEL_H_ */