/*
 *
 * (C) COPYRIGHT 2008-2013 ARM Limited. All rights reserved.
 *
 * This program is free software and is provided to you under the terms of the
 * GNU General Public License version 2 as published by the Free Software
 * Foundation, and any use by you of this program is subject to the terms
 * of such GNU licence.
 *
 * A copy of the licence is included with the program, and can also be obtained
 * from Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
 * Boston, MA  02110-1301, USA.
 *
 */


/**
 * @file ump_kernel_descriptor_mapping.h
 */

#ifndef _UMP_KERNEL_DESCRIPTOR_MAPPING_H_
#define _UMP_KERNEL_DESCRIPTOR_MAPPING_H_

#include <linux/rwsem.h>
#include <linux/slab.h>
/**
 * The actual descriptor mapping table, never directly accessed by clients
 */
typedef struct umpp_descriptor_table
{
	/* keep as a unsigned long to rely on the OS's bitops support */
	unsigned long * usage; /**< Pointer to bitpattern indicating if a descriptor is valid/used(1) or not(0) */
	void** mappings; /**< Array of the pointers the descriptors map to */
} umpp_descriptor_table;

/**
 * The descriptor mapping object
 * Provides a separate namespace where we can map an integer to a pointer
 */
typedef struct umpp_descriptor_mapping
{
	struct rw_semaphore lock; /**< Lock protecting access to the mapping object */
	unsigned int max_nr_mappings_allowed; /**< Max number of mappings to support in this namespace */
	unsigned int current_nr_mappings; /**< Current number of possible mappings */
	umpp_descriptor_table * table; /**< Pointer to the current mapping table */
} umpp_descriptor_mapping;

/**
 * Create a descriptor mapping object.
 * Create a descriptor mapping capable of holding init_entries growable to max_entries.
 * ID 0 is reserved so the number of available entries will be max - 1.
 * @param init_entries Number of entries to preallocate memory for
 * @param max_entries Number of entries to max support
 * @return Pointer to a descriptor mapping object, NULL on failure
 */
umpp_descriptor_mapping * umpp_descriptor_mapping_create(unsigned int init_entries, unsigned int max_entries);

/**
 * Destroy a descriptor mapping object
 * @param[in] map The map to free
 */
void umpp_descriptor_mapping_destroy(umpp_descriptor_mapping * map);

/**
 * Allocate a new mapping entry (descriptor ID)
 * Allocates a new entry in the map.
 * @param[in] map The map to allocate a new entry in
 * @param[in] target The value to map to
 * @return The descriptor allocated, ID 0 on failure.
 */
unsigned int umpp_descriptor_mapping_allocate(umpp_descriptor_mapping * map, void * target);

/**
 * Get the value mapped to by a descriptor ID
 * @param[in] map The map to lookup the descriptor id in
 * @param[in] descriptor The descriptor ID to lookup
 * @param[out] target Pointer to a pointer which will receive the stored value
 *
 * @return 0 on success lookup, -EINVAL on lookup failure.
 */
int umpp_descriptor_mapping_lookup(umpp_descriptor_mapping * map, unsigned int descriptor, void** const target);

/**
 * Free the descriptor ID
 * For the descriptor to be reused it has to be freed
 * @param[in] map The map to free the descriptor from
 * @param descriptor The descriptor ID to free
 */
void umpp_descriptor_mapping_remove(umpp_descriptor_mapping * map, unsigned int descriptor);

#endif /* _UMP_KERNEL_DESCRIPTOR_MAPPING_H_ */