/*
   * Copyright (C) 2003 Sistina Software.
   * Copyright (C) 2004 Red Hat, Inc. All rights reserved.
   *
   * Module Author: Heinz Mauelshagen
   *
   * This file is released under the GPL.
   *
   * Path-Selector registration.
   */
  
  #ifndef	DM_PATH_SELECTOR_H
  #define	DM_PATH_SELECTOR_H
  
  #include <linux/device-mapper.h>
  
  #include "dm-mpath.h"
  
  /*
   * We provide an abstraction for the code that chooses which path
   * to send some io down.
   */
  struct path_selector_type;
  struct path_selector {
  	struct path_selector_type *type;
  	void *context;
  };
  
  /* Information about a path selector type */
  struct path_selector_type {
  	char *name;
  	struct module *module;
  
  	unsigned int table_args;
  	unsigned int info_args;
  
  	/*
  	 * Constructs a path selector object, takes custom arguments
  	 */
  	int (*create) (struct path_selector *ps, unsigned argc, char **argv);
  	void (*destroy) (struct path_selector *ps);
  
  	/*
  	 * Add an opaque path object, along with some selector specific
  	 * path args (eg, path priority).
  	 */
  	int (*add_path) (struct path_selector *ps, struct dm_path *path,
  			 int argc, char **argv, char **error);
  
  	/*
  	 * Chooses a path for this io, if no paths are available then
  	 * NULL will be returned.
  	 *
  	 * repeat_count is the number of times to use the path before
  	 * calling the function again.  0 means don't call it again unless
  	 * the path fails.
  	 */
  	struct dm_path *(*select_path) (struct path_selector *ps,
  					unsigned *repeat_count,
  					size_t nr_bytes);
  
  	/*
  	 * Notify the selector that a path has failed.
  	 */
  	void (*fail_path) (struct path_selector *ps, struct dm_path *p);
  
  	/*
  	 * Ask selector to reinstate a path.
  	 */
  	int (*reinstate_path) (struct path_selector *ps, struct dm_path *p);
  
  	/*
  	 * Table content based on parameters added in ps_add_path_fn
  	 * or path selector status
  	 */
  	int (*status) (struct path_selector *ps, struct dm_path *path,
  		       status_type_t type, char *result, unsigned int maxlen);
  
  	int (*start_io) (struct path_selector *ps, struct dm_path *path,
  			 size_t nr_bytes);
  	int (*end_io) (struct path_selector *ps, struct dm_path *path,
  		       size_t nr_bytes);
  };
  
  /* Register a path selector */
  int dm_register_path_selector(struct path_selector_type *type);
  
  /* Unregister a path selector */
  int dm_unregister_path_selector(struct path_selector_type *type);
  
  /* Returns a registered path selector type */
  struct path_selector_type *dm_get_path_selector(const char *name);
  
  /* Releases a path selector  */
  void dm_put_path_selector(struct path_selector_type *pst);
  
  #endif