/*
   * Basic general purpose allocator for managing special purpose memory
   * not managed by the regular kmalloc/kfree interface.
   * Uses for this includes on-device special memory, uncached memory
   * etc.
   *

   * Copyright 2005 (C) Jes Sorensen <jes@trained-monkey.org>
   *
   * This source code is licensed under the GNU General Public License,
   * Version 2.  See the file COPYING for more details.
   */

  #include <linux/slab.h>

  #include <linux/module.h>

  #include <linux/bitmap.h>

  #include <linux/genalloc.h>

  /**
   * gen_pool_create - create a new special memory pool

   * @min_alloc_order: log base 2 of number of bytes each bitmap bit represents
   * @nid: node id of the node the pool structure should be allocated on, or -1

   *
   * Create a new special memory pool that can be used to manage special purpose
   * memory not managed by the regular kmalloc/kfree interface.

   */
  struct gen_pool *gen_pool_create(int min_alloc_order, int nid)

  {

  	struct gen_pool *pool;

  	pool = kmalloc_node(sizeof(struct gen_pool), GFP_KERNEL, nid);
  	if (pool != NULL) {
  		rwlock_init(&pool->lock);
  		INIT_LIST_HEAD(&pool->chunks);
  		pool->min_alloc_order = min_alloc_order;
  	}
  	return pool;

  }
  EXPORT_SYMBOL(gen_pool_create);

  /**
   * gen_pool_add - add a new chunk of special memory to the pool

   * @pool: pool to add new memory chunk to
   * @addr: starting address of memory chunk to add to pool
   * @size: size in bytes of the memory chunk to add to pool
   * @nid: node id of the node the chunk structure and bitmap should be
   *       allocated on, or -1

   *
   * Add a new chunk of special memory to the specified pool.

   */

  int gen_pool_add(struct gen_pool *pool, unsigned long addr, size_t size,
  		 int nid)

  {

  	struct gen_pool_chunk *chunk;
  	int nbits = size >> pool->min_alloc_order;
  	int nbytes = sizeof(struct gen_pool_chunk) +
  				(nbits + BITS_PER_BYTE - 1) / BITS_PER_BYTE;

  	chunk = kmalloc_node(nbytes, GFP_KERNEL | __GFP_ZERO, nid);

  	if (unlikely(chunk == NULL))
  		return -1;

  	spin_lock_init(&chunk->lock);
  	chunk->start_addr = addr;
  	chunk->end_addr = addr + size;

  	write_lock(&pool->lock);
  	list_add(&chunk->next_chunk, &pool->chunks);
  	write_unlock(&pool->lock);
  
  	return 0;

  }

  EXPORT_SYMBOL(gen_pool_add);

  /**
   * gen_pool_destroy - destroy a special memory pool

   * @pool: pool to destroy

   *
   * Destroy the specified special memory pool. Verifies that there are no
   * outstanding allocations.

   */
  void gen_pool_destroy(struct gen_pool *pool)
  {
  	struct list_head *_chunk, *_next_chunk;
  	struct gen_pool_chunk *chunk;
  	int order = pool->min_alloc_order;
  	int bit, end_bit;

  	list_for_each_safe(_chunk, _next_chunk, &pool->chunks) {
  		chunk = list_entry(_chunk, struct gen_pool_chunk, next_chunk);
  		list_del(&chunk->next_chunk);
  
  		end_bit = (chunk->end_addr - chunk->start_addr) >> order;
  		bit = find_next_bit(chunk->bits, end_bit, 0);
  		BUG_ON(bit < end_bit);
  
  		kfree(chunk);
  	}
  	kfree(pool);
  	return;
  }
  EXPORT_SYMBOL(gen_pool_destroy);

  /**
   * gen_pool_alloc - allocate special memory from the pool

   * @pool: pool to allocate from
   * @size: number of bytes to allocate from the pool

   *
   * Allocate the requested number of bytes from the specified pool.
   * Uses a first-fit algorithm.

   */

  unsigned long gen_pool_alloc(struct gen_pool *pool, size_t size)

  {

  	struct list_head *_chunk;
  	struct gen_pool_chunk *chunk;
  	unsigned long addr, flags;
  	int order = pool->min_alloc_order;

  	int nbits, start_bit, end_bit;

  	if (size == 0)
  		return 0;

  	nbits = (size + (1UL << order) - 1) >> order;
  
  	read_lock(&pool->lock);
  	list_for_each(_chunk, &pool->chunks) {
  		chunk = list_entry(_chunk, struct gen_pool_chunk, next_chunk);
  
  		end_bit = (chunk->end_addr - chunk->start_addr) >> order;

  
  		spin_lock_irqsave(&chunk->lock, flags);

  		start_bit = bitmap_find_next_zero_area(chunk->bits, end_bit, 0,
  						nbits, 0);
  		if (start_bit >= end_bit) {

  			spin_unlock_irqrestore(&chunk->lock, flags);

  			continue;

  		}

  
  		addr = chunk->start_addr + ((unsigned long)start_bit << order);
  
  		bitmap_set(chunk->bits, start_bit, nbits);

  		spin_unlock_irqrestore(&chunk->lock, flags);

  		read_unlock(&pool->lock);
  		return addr;

  	}
  	read_unlock(&pool->lock);
  	return 0;
  }
  EXPORT_SYMBOL(gen_pool_alloc);

  /**
   * gen_pool_free - free allocated special memory back to the pool

   * @pool: pool to free to
   * @addr: starting address of memory to free back to pool
   * @size: size in bytes of memory to free

   *
   * Free previously allocated special memory back to the specified pool.

   */
  void gen_pool_free(struct gen_pool *pool, unsigned long addr, size_t size)
  {
  	struct list_head *_chunk;
  	struct gen_pool_chunk *chunk;
  	unsigned long flags;
  	int order = pool->min_alloc_order;
  	int bit, nbits;
  
  	nbits = (size + (1UL << order) - 1) >> order;
  
  	read_lock(&pool->lock);
  	list_for_each(_chunk, &pool->chunks) {
  		chunk = list_entry(_chunk, struct gen_pool_chunk, next_chunk);
  
  		if (addr >= chunk->start_addr && addr < chunk->end_addr) {
  			BUG_ON(addr + size > chunk->end_addr);
  			spin_lock_irqsave(&chunk->lock, flags);
  			bit = (addr - chunk->start_addr) >> order;
  			while (nbits--)

  				__clear_bit(bit++, chunk->bits);

  			spin_unlock_irqrestore(&chunk->lock, flags);

  			break;
  		}

  	}

  	BUG_ON(nbits > 0);
  	read_unlock(&pool->lock);

  }
  EXPORT_SYMBOL(gen_pool_free);