lib/genalloc.c - kernel/msm-5.4 - Gitiles

 /*
  * Basic general purpose allocator for managing special purpose
  * memory, for example, memory that is not managed by the regular
  * kmalloc/kfree interface.  Uses for this includes on-device special
  * memory, uncached memory etc.
  *
  * It is safe to use the allocator in NMI handlers and other special
  * unblockable contexts that could otherwise deadlock on locks.  This
  * is implemented by using atomic operations and retries on any
  * conflicts.  The disadvantage is that there may be livelocks in
  * extreme cases.  For better scalability, one allocator can be used
  * for each CPU.
  *
  * The lockless operation only works if there is enough memory
  * available.  If new memory is added to the pool a lock has to be
  * still taken.  So any user relying on locklessness has to ensure
  * that sufficient memory is preallocated.
  *
  * The basic atomic operation of this allocator is cmpxchg on long.
  * On architectures that don't have NMI-safe cmpxchg implementation,
  * the allocator can NOT be used in NMI handler.  So code uses the
  * allocator in NMI handler should depend on
  * CONFIG_ARCH_HAVE_NMI_SAFE_CMPXCHG.
  *
  * 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/export.h>
 #include <linux/bitmap.h>
 #include <linux/rculist.h>
 #include <linux/interrupt.h>
 #include <linux/genalloc.h>
 #include <linux/of_address.h>
 #include <linux/of_device.h>

 static inline size_t chunk_size(const struct gen_pool_chunk *chunk)
 {
 	return chunk->end_addr - chunk->start_addr + 1;
 }

 static int set_bits_ll(unsigned long *addr, unsigned long mask_to_set)
 {
 	unsigned long val, nval;

 	nval = *addr;
 	do {
 		val = nval;
 		if (val & mask_to_set)
 			return -EBUSY;
 		cpu_relax();
 	} while ((nval = cmpxchg(addr, val, val | mask_to_set)) != val);

 	return 0;
 }

 static int clear_bits_ll(unsigned long *addr, unsigned long mask_to_clear)
 {
 	unsigned long val, nval;

 	nval = *addr;
 	do {
 		val = nval;
 		if ((val & mask_to_clear) != mask_to_clear)
 			return -EBUSY;
 		cpu_relax();
 	} while ((nval = cmpxchg(addr, val, val & ~mask_to_clear)) != val);

 	return 0;
 }

 /*
  * bitmap_set_ll - set the specified number of bits at the specified position
  * @map: pointer to a bitmap
  * @start: a bit position in @map
  * @nr: number of bits to set
  *
  * Set @nr bits start from @start in @map lock-lessly. Several users
  * can set/clear the same bitmap simultaneously without lock. If two
  * users set the same bit, one user will return remain bits, otherwise
  * return 0.
  */
 static int bitmap_set_ll(unsigned long *map, int start, int nr)
 {
 	unsigned long *p = map + BIT_WORD(start);
 	const int size = start + nr;
 	int bits_to_set = BITS_PER_LONG - (start % BITS_PER_LONG);
 	unsigned long mask_to_set = BITMAP_FIRST_WORD_MASK(start);

 	while (nr - bits_to_set >= 0) {
 		if (set_bits_ll(p, mask_to_set))
 			return nr;
 		nr -= bits_to_set;
 		bits_to_set = BITS_PER_LONG;
 		mask_to_set = ~0UL;
 		p++;
 	}
 	if (nr) {
 		mask_to_set &= BITMAP_LAST_WORD_MASK(size);
 		if (set_bits_ll(p, mask_to_set))
 			return nr;
 	}

 	return 0;
 }

 /*
  * bitmap_clear_ll - clear the specified number of bits at the specified position
  * @map: pointer to a bitmap
  * @start: a bit position in @map
  * @nr: number of bits to set
  *
  * Clear @nr bits start from @start in @map lock-lessly. Several users
  * can set/clear the same bitmap simultaneously without lock. If two
  * users clear the same bit, one user will return remain bits,
  * otherwise return 0.
  */
 static int bitmap_clear_ll(unsigned long *map, int start, int nr)
 {
 	unsigned long *p = map + BIT_WORD(start);
 	const int size = start + nr;
 	int bits_to_clear = BITS_PER_LONG - (start % BITS_PER_LONG);
 	unsigned long mask_to_clear = BITMAP_FIRST_WORD_MASK(start);

 	while (nr - bits_to_clear >= 0) {
 		if (clear_bits_ll(p, mask_to_clear))
 			return nr;
 		nr -= bits_to_clear;
 		bits_to_clear = BITS_PER_LONG;
 		mask_to_clear = ~0UL;
 		p++;
 	}
 	if (nr) {
 		mask_to_clear &= BITMAP_LAST_WORD_MASK(size);
 		if (clear_bits_ll(p, mask_to_clear))
 			return nr;
 	}

 	return 0;
 }

 /**
  * 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) {
 		spin_lock_init(&pool->lock);
 		INIT_LIST_HEAD(&pool->chunks);
 		pool->min_alloc_order = min_alloc_order;
 		pool->algo = gen_pool_first_fit;
 		pool->data = NULL;
 	}
 	return pool;
 }
 EXPORT_SYMBOL(gen_pool_create);

 /**
  * gen_pool_add_virt - add a new chunk of special memory to the pool
  * @pool: pool to add new memory chunk to
  * @virt: virtual starting address of memory chunk to add to pool
  * @phys: physical 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.
  *
  * Returns 0 on success or a -ve errno on failure.
  */
 int gen_pool_add_virt(struct gen_pool *pool, unsigned long virt, phys_addr_t phys,
 		 size_t size, int nid)
 {
 	struct gen_pool_chunk *chunk;
 	int nbits = size >> pool->min_alloc_order;
 	int nbytes = sizeof(struct gen_pool_chunk) +
 				BITS_TO_LONGS(nbits) * sizeof(long);

 	chunk = kzalloc_node(nbytes, GFP_KERNEL, nid);
 	if (unlikely(chunk == NULL))
 		return -ENOMEM;

 	chunk->phys_addr = phys;
 	chunk->start_addr = virt;
 	chunk->end_addr = virt + size - 1;
 	atomic_set(&chunk->avail, size);

 	spin_lock(&pool->lock);
 	list_add_rcu(&chunk->next_chunk, &pool->chunks);
 	spin_unlock(&pool->lock);

 	return 0;
 }
 EXPORT_SYMBOL(gen_pool_add_virt);

 /**
  * gen_pool_virt_to_phys - return the physical address of memory
  * @pool: pool to allocate from
  * @addr: starting address of memory
  *
  * Returns the physical address on success, or -1 on error.
  */
 phys_addr_t gen_pool_virt_to_phys(struct gen_pool *pool, unsigned long addr)
 {
 	struct gen_pool_chunk *chunk;
 	phys_addr_t paddr = -1;

 	rcu_read_lock();
 	list_for_each_entry_rcu(chunk, &pool->chunks, next_chunk) {
 		if (addr >= chunk->start_addr && addr <= chunk->end_addr) {
 			paddr = chunk->phys_addr + (addr - chunk->start_addr);
 			break;
 		}
 	}
 	rcu_read_unlock();

 	return paddr;
 }
 EXPORT_SYMBOL(gen_pool_virt_to_phys);

 /**
  * 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_size(chunk) >> 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 the pool allocation function (with first-fit algorithm by default).
  * Can not be used in NMI handler on architectures without
  * NMI-safe cmpxchg implementation.
  */
 unsigned long gen_pool_alloc(struct gen_pool *pool, size_t size)
 {
 	struct gen_pool_chunk *chunk;
 	unsigned long addr = 0;
 	int order = pool->min_alloc_order;
 	int nbits, start_bit = 0, end_bit, remain;

 #ifndef CONFIG_ARCH_HAVE_NMI_SAFE_CMPXCHG
 	BUG_ON(in_nmi());
 #endif

 	if (size == 0)
 		return 0;

 	nbits = (size + (1UL << order) - 1) >> order;
 	rcu_read_lock();
 	list_for_each_entry_rcu(chunk, &pool->chunks, next_chunk) {
 		if (size > atomic_read(&chunk->avail))
 			continue;

 		end_bit = chunk_size(chunk) >> order;
 retry:
 		start_bit = pool->algo(chunk->bits, end_bit, start_bit, nbits,
 				pool->data);
 		if (start_bit >= end_bit)
 			continue;
 		remain = bitmap_set_ll(chunk->bits, start_bit, nbits);
 		if (remain) {
 			remain = bitmap_clear_ll(chunk->bits, start_bit,
 						 nbits - remain);
 			BUG_ON(remain);
 			goto retry;
 		}

 		addr = chunk->start_addr + ((unsigned long)start_bit << order);
 		size = nbits << order;
 		atomic_sub(size, &chunk->avail);
 		break;
 	}
 	rcu_read_unlock();
 	return addr;
 }
 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.  Can not be used in NMI handler on architectures without
  * NMI-safe cmpxchg implementation.
  */
 void gen_pool_free(struct gen_pool *pool, unsigned long addr, size_t size)
 {
 	struct gen_pool_chunk *chunk;
 	int order = pool->min_alloc_order;
 	int start_bit, nbits, remain;

 #ifndef CONFIG_ARCH_HAVE_NMI_SAFE_CMPXCHG
 	BUG_ON(in_nmi());
 #endif

 	nbits = (size + (1UL << order) - 1) >> order;
 	rcu_read_lock();
 	list_for_each_entry_rcu(chunk, &pool->chunks, next_chunk) {
 		if (addr >= chunk->start_addr && addr <= chunk->end_addr) {
 			BUG_ON(addr + size - 1 > chunk->end_addr);
 			start_bit = (addr - chunk->start_addr) >> order;
 			remain = bitmap_clear_ll(chunk->bits, start_bit, nbits);
 			BUG_ON(remain);
 			size = nbits << order;
 			atomic_add(size, &chunk->avail);
 			rcu_read_unlock();
 			return;
 		}
 	}
 	rcu_read_unlock();
 	BUG();
 }
 EXPORT_SYMBOL(gen_pool_free);

 /**
  * gen_pool_for_each_chunk - call func for every chunk of generic memory pool
  * @pool:	the generic memory pool
  * @func:	func to call
  * @data:	additional data used by @func
  *
  * Call @func for every chunk of generic memory pool.  The @func is
  * called with rcu_read_lock held.
  */
 void gen_pool_for_each_chunk(struct gen_pool *pool,
 	void (*func)(struct gen_pool *pool, struct gen_pool_chunk *chunk, void *data),
 	void *data)
 {
 	struct gen_pool_chunk *chunk;

 	rcu_read_lock();
 	list_for_each_entry_rcu(chunk, &(pool)->chunks, next_chunk)
 		func(pool, chunk, data);
 	rcu_read_unlock();
 }
 EXPORT_SYMBOL(gen_pool_for_each_chunk);

 /**
  * gen_pool_avail - get available free space of the pool
  * @pool: pool to get available free space
  *
  * Return available free space of the specified pool.
  */
 size_t gen_pool_avail(struct gen_pool *pool)
 {
 	struct gen_pool_chunk *chunk;
 	size_t avail = 0;

 	rcu_read_lock();
 	list_for_each_entry_rcu(chunk, &pool->chunks, next_chunk)
 		avail += atomic_read(&chunk->avail);
 	rcu_read_unlock();
 	return avail;
 }
 EXPORT_SYMBOL_GPL(gen_pool_avail);

 /**
  * gen_pool_size - get size in bytes of memory managed by the pool
  * @pool: pool to get size
  *
  * Return size in bytes of memory managed by the pool.
  */
 size_t gen_pool_size(struct gen_pool *pool)
 {
 	struct gen_pool_chunk *chunk;
 	size_t size = 0;

 	rcu_read_lock();
 	list_for_each_entry_rcu(chunk, &pool->chunks, next_chunk)
 		size += chunk_size(chunk);
 	rcu_read_unlock();
 	return size;
 }
 EXPORT_SYMBOL_GPL(gen_pool_size);

 /**
  * gen_pool_set_algo - set the allocation algorithm
  * @pool: pool to change allocation algorithm
  * @algo: custom algorithm function
  * @data: additional data used by @algo
  *
  * Call @algo for each memory allocation in the pool.
  * If @algo is NULL use gen_pool_first_fit as default
  * memory allocation function.
  */
 void gen_pool_set_algo(struct gen_pool *pool, genpool_algo_t algo, void *data)
 {
 	rcu_read_lock();

 	pool->algo = algo;
 	if (!pool->algo)
 		pool->algo = gen_pool_first_fit;

 	pool->data = data;

 	rcu_read_unlock();
 }
 EXPORT_SYMBOL(gen_pool_set_algo);

 /**
  * gen_pool_first_fit - find the first available region
  * of memory matching the size requirement (no alignment constraint)
  * @map: The address to base the search on
  * @size: The bitmap size in bits
  * @start: The bitnumber to start searching at
  * @nr: The number of zeroed bits we're looking for
  * @data: additional data - unused
  */
 unsigned long gen_pool_first_fit(unsigned long *map, unsigned long size,
 		unsigned long start, unsigned int nr, void *data)
 {
 	return bitmap_find_next_zero_area(map, size, start, nr, 0);
 }
 EXPORT_SYMBOL(gen_pool_first_fit);

 /**
  * gen_pool_best_fit - find the best fitting region of memory
  * macthing the size requirement (no alignment constraint)
  * @map: The address to base the search on
  * @size: The bitmap size in bits
  * @start: The bitnumber to start searching at
  * @nr: The number of zeroed bits we're looking for
  * @data: additional data - unused
  *
  * Iterate over the bitmap to find the smallest free region
  * which we can allocate the memory.
  */
 unsigned long gen_pool_best_fit(unsigned long *map, unsigned long size,
 		unsigned long start, unsigned int nr, void *data)
 {
 	unsigned long start_bit = size;
 	unsigned long len = size + 1;
 	unsigned long index;

 	index = bitmap_find_next_zero_area(map, size, start, nr, 0);

 	while (index < size) {
 		int next_bit = find_next_bit(map, size, index + nr);
 		if ((next_bit - index) < len) {
 			len = next_bit - index;
 			start_bit = index;
 			if (len == nr)
 				return start_bit;
 		}
 		index = bitmap_find_next_zero_area(map, size,
 						   next_bit + 1, nr, 0);
 	}

 	return start_bit;
 }
 EXPORT_SYMBOL(gen_pool_best_fit);

 static void devm_gen_pool_release(struct device *dev, void *res)
 {
 	gen_pool_destroy(*(struct gen_pool **)res);
 }

 /**
  * devm_gen_pool_create - managed gen_pool_create
  * @dev: device that provides the gen_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. The pool will be
  * automatically destroyed by the device management code.
  */
 struct gen_pool *devm_gen_pool_create(struct device *dev, int min_alloc_order,
 		int nid)
 {
 	struct gen_pool **ptr, *pool;

 	ptr = devres_alloc(devm_gen_pool_release, sizeof(*ptr), GFP_KERNEL);

 	pool = gen_pool_create(min_alloc_order, nid);
 	if (pool) {
 		*ptr = pool;
 		devres_add(dev, ptr);
 	} else {
 		devres_free(ptr);
 	}

 	return pool;
 }

 /**
  * dev_get_gen_pool - Obtain the gen_pool (if any) for a device
  * @dev: device to retrieve the gen_pool from
  * @name: Optional name for the gen_pool, usually NULL
  *
  * Returns the gen_pool for the device if one is present, or NULL.
  */
 struct gen_pool *dev_get_gen_pool(struct device *dev)
 {
 	struct gen_pool **p = devres_find(dev, devm_gen_pool_release, NULL,
 					NULL);

 	if (!p)
 		return NULL;
 	return *p;
 }
 EXPORT_SYMBOL_GPL(dev_get_gen_pool);

 #ifdef CONFIG_OF
 /**
  * of_get_named_gen_pool - find a pool by phandle property
  * @np: device node
  * @propname: property name containing phandle(s)
  * @index: index into the phandle array
  *
  * Returns the pool that contains the chunk starting at the physical
  * address of the device tree node pointed at by the phandle property,
  * or NULL if not found.
  */
 struct gen_pool *of_get_named_gen_pool(struct device_node *np,
 	const char *propname, int index)
 {
 	struct platform_device *pdev;
 	struct device_node *np_pool;

 	np_pool = of_parse_phandle(np, propname, index);
 	if (!np_pool)
 		return NULL;
 	pdev = of_find_device_by_node(np_pool);
 	if (!pdev)
 		return NULL;
 	return dev_get_gen_pool(&pdev->dev);
 }
 EXPORT_SYMBOL_GPL(of_get_named_gen_pool);
 #endif /* CONFIG_OF */
	/*
	* Basic general purpose allocator for managing special purpose
	* memory, for example, memory that is not managed by the regular
	* kmalloc/kfree interface. Uses for this includes on-device special
	* memory, uncached memory etc.
	*
	* It is safe to use the allocator in NMI handlers and other special
	* unblockable contexts that could otherwise deadlock on locks. This
	* is implemented by using atomic operations and retries on any
	* conflicts. The disadvantage is that there may be livelocks in
	* extreme cases. For better scalability, one allocator can be used
	* for each CPU.
	*
	* The lockless operation only works if there is enough memory
	* available. If new memory is added to the pool a lock has to be
	* still taken. So any user relying on locklessness has to ensure
	* that sufficient memory is preallocated.
	*
	* The basic atomic operation of this allocator is cmpxchg on long.
	* On architectures that don't have NMI-safe cmpxchg implementation,
	* the allocator can NOT be used in NMI handler. So code uses the
	* allocator in NMI handler should depend on
	* CONFIG_ARCH_HAVE_NMI_SAFE_CMPXCHG.
	*
	* 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/export.h>
	#include <linux/bitmap.h>
	#include <linux/rculist.h>
	#include <linux/interrupt.h>
	#include <linux/genalloc.h>
	#include <linux/of_address.h>
	#include <linux/of_device.h>

	static inline size_t chunk_size(const struct gen_pool_chunk *chunk)
	{
	return chunk->end_addr - chunk->start_addr + 1;
	}

	static int set_bits_ll(unsigned long *addr, unsigned long mask_to_set)
	{
	unsigned long val, nval;

	nval = *addr;
	do {
	val = nval;
	if (val & mask_to_set)
	return -EBUSY;
	cpu_relax();
	} while ((nval = cmpxchg(addr, val, val \| mask_to_set)) != val);

	return 0;
	}

	static int clear_bits_ll(unsigned long *addr, unsigned long mask_to_clear)
	{
	unsigned long val, nval;

	nval = *addr;
	do {
	val = nval;
	if ((val & mask_to_clear) != mask_to_clear)
	return -EBUSY;
	cpu_relax();
	} while ((nval = cmpxchg(addr, val, val & ~mask_to_clear)) != val);

	return 0;
	}

	/*
	* bitmap_set_ll - set the specified number of bits at the specified position
	* @map: pointer to a bitmap
	* @start: a bit position in @map
	* @nr: number of bits to set
	*
	* Set @nr bits start from @start in @map lock-lessly. Several users
	* can set/clear the same bitmap simultaneously without lock. If two
	* users set the same bit, one user will return remain bits, otherwise
	* return 0.
	*/
	static int bitmap_set_ll(unsigned long *map, int start, int nr)
	{
	unsigned long *p = map + BIT_WORD(start);
	const int size = start + nr;
	int bits_to_set = BITS_PER_LONG - (start % BITS_PER_LONG);
	unsigned long mask_to_set = BITMAP_FIRST_WORD_MASK(start);

	while (nr - bits_to_set >= 0) {
	if (set_bits_ll(p, mask_to_set))
	return nr;
	nr -= bits_to_set;
	bits_to_set = BITS_PER_LONG;
	mask_to_set = ~0UL;
	p++;
	}
	if (nr) {
	mask_to_set &= BITMAP_LAST_WORD_MASK(size);
	if (set_bits_ll(p, mask_to_set))
	return nr;
	}

	return 0;
	}

	/*
	* bitmap_clear_ll - clear the specified number of bits at the specified position
	* @map: pointer to a bitmap
	* @start: a bit position in @map
	* @nr: number of bits to set
	*
	* Clear @nr bits start from @start in @map lock-lessly. Several users
	* can set/clear the same bitmap simultaneously without lock. If two
	* users clear the same bit, one user will return remain bits,
	* otherwise return 0.
	*/
	static int bitmap_clear_ll(unsigned long *map, int start, int nr)
	{
	unsigned long *p = map + BIT_WORD(start);
	const int size = start + nr;
	int bits_to_clear = BITS_PER_LONG - (start % BITS_PER_LONG);
	unsigned long mask_to_clear = BITMAP_FIRST_WORD_MASK(start);

	while (nr - bits_to_clear >= 0) {
	if (clear_bits_ll(p, mask_to_clear))
	return nr;
	nr -= bits_to_clear;
	bits_to_clear = BITS_PER_LONG;
	mask_to_clear = ~0UL;
	p++;
	}
	if (nr) {
	mask_to_clear &= BITMAP_LAST_WORD_MASK(size);
	if (clear_bits_ll(p, mask_to_clear))
	return nr;
	}

	return 0;
	}

	/**
	* 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) {
	spin_lock_init(&pool->lock);
	INIT_LIST_HEAD(&pool->chunks);
	pool->min_alloc_order = min_alloc_order;
	pool->algo = gen_pool_first_fit;
	pool->data = NULL;
	}
	return pool;
	}
	EXPORT_SYMBOL(gen_pool_create);

	/**
	* gen_pool_add_virt - add a new chunk of special memory to the pool
	* @pool: pool to add new memory chunk to
	* @virt: virtual starting address of memory chunk to add to pool
	* @phys: physical 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.
	*
	* Returns 0 on success or a -ve errno on failure.
	*/
	int gen_pool_add_virt(struct gen_pool *pool, unsigned long virt, phys_addr_t phys,
	size_t size, int nid)
	{
	struct gen_pool_chunk *chunk;
	int nbits = size >> pool->min_alloc_order;
	int nbytes = sizeof(struct gen_pool_chunk) +
	BITS_TO_LONGS(nbits) * sizeof(long);

	chunk = kzalloc_node(nbytes, GFP_KERNEL, nid);
	if (unlikely(chunk == NULL))
	return -ENOMEM;

	chunk->phys_addr = phys;
	chunk->start_addr = virt;
	chunk->end_addr = virt + size - 1;
	atomic_set(&chunk->avail, size);

	spin_lock(&pool->lock);
	list_add_rcu(&chunk->next_chunk, &pool->chunks);
	spin_unlock(&pool->lock);

	return 0;
	}
	EXPORT_SYMBOL(gen_pool_add_virt);

	/**
	* gen_pool_virt_to_phys - return the physical address of memory
	* @pool: pool to allocate from
	* @addr: starting address of memory
	*
	* Returns the physical address on success, or -1 on error.
	*/
	phys_addr_t gen_pool_virt_to_phys(struct gen_pool *pool, unsigned long addr)
	{
	struct gen_pool_chunk *chunk;
	phys_addr_t paddr = -1;

	rcu_read_lock();
	list_for_each_entry_rcu(chunk, &pool->chunks, next_chunk) {
	if (addr >= chunk->start_addr && addr <= chunk->end_addr) {
	paddr = chunk->phys_addr + (addr - chunk->start_addr);
	break;
	}
	}
	rcu_read_unlock();

	return paddr;
	}
	EXPORT_SYMBOL(gen_pool_virt_to_phys);

	/**
	* 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_size(chunk) >> 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 the pool allocation function (with first-fit algorithm by default).
	* Can not be used in NMI handler on architectures without
	* NMI-safe cmpxchg implementation.
	*/
	unsigned long gen_pool_alloc(struct gen_pool *pool, size_t size)
	{
	struct gen_pool_chunk *chunk;
	unsigned long addr = 0;
	int order = pool->min_alloc_order;
	int nbits, start_bit = 0, end_bit, remain;

	#ifndef CONFIG_ARCH_HAVE_NMI_SAFE_CMPXCHG
	BUG_ON(in_nmi());
	#endif

	if (size == 0)
	return 0;

	nbits = (size + (1UL << order) - 1) >> order;
	rcu_read_lock();
	list_for_each_entry_rcu(chunk, &pool->chunks, next_chunk) {
	if (size > atomic_read(&chunk->avail))
	continue;

	end_bit = chunk_size(chunk) >> order;
	retry:
	start_bit = pool->algo(chunk->bits, end_bit, start_bit, nbits,
	pool->data);
	if (start_bit >= end_bit)
	continue;
	remain = bitmap_set_ll(chunk->bits, start_bit, nbits);
	if (remain) {
	remain = bitmap_clear_ll(chunk->bits, start_bit,
	nbits - remain);
	BUG_ON(remain);
	goto retry;
	}

	addr = chunk->start_addr + ((unsigned long)start_bit << order);
	size = nbits << order;
	atomic_sub(size, &chunk->avail);
	break;
	}
	rcu_read_unlock();
	return addr;
	}
	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. Can not be used in NMI handler on architectures without
	* NMI-safe cmpxchg implementation.
	*/
	void gen_pool_free(struct gen_pool *pool, unsigned long addr, size_t size)
	{
	struct gen_pool_chunk *chunk;
	int order = pool->min_alloc_order;
	int start_bit, nbits, remain;

	#ifndef CONFIG_ARCH_HAVE_NMI_SAFE_CMPXCHG
	BUG_ON(in_nmi());
	#endif

	nbits = (size + (1UL << order) - 1) >> order;
	rcu_read_lock();
	list_for_each_entry_rcu(chunk, &pool->chunks, next_chunk) {
	if (addr >= chunk->start_addr && addr <= chunk->end_addr) {
	BUG_ON(addr + size - 1 > chunk->end_addr);
	start_bit = (addr - chunk->start_addr) >> order;
	remain = bitmap_clear_ll(chunk->bits, start_bit, nbits);
	BUG_ON(remain);
	size = nbits << order;
	atomic_add(size, &chunk->avail);
	rcu_read_unlock();
	return;
	}
	}
	rcu_read_unlock();
	BUG();
	}
	EXPORT_SYMBOL(gen_pool_free);

	/**
	* gen_pool_for_each_chunk - call func for every chunk of generic memory pool
	* @pool: the generic memory pool
	* @func: func to call
	* @data: additional data used by @func
	*
	* Call @func for every chunk of generic memory pool. The @func is
	* called with rcu_read_lock held.
	*/
	void gen_pool_for_each_chunk(struct gen_pool *pool,
	void (func)(struct gen_pool pool, struct gen_pool_chunk chunk, void data),
	void *data)
	{
	struct gen_pool_chunk *chunk;

	rcu_read_lock();
	list_for_each_entry_rcu(chunk, &(pool)->chunks, next_chunk)
	func(pool, chunk, data);
	rcu_read_unlock();
	}
	EXPORT_SYMBOL(gen_pool_for_each_chunk);

	/**
	* gen_pool_avail - get available free space of the pool
	* @pool: pool to get available free space
	*
	* Return available free space of the specified pool.
	*/
	size_t gen_pool_avail(struct gen_pool *pool)
	{
	struct gen_pool_chunk *chunk;
	size_t avail = 0;

	rcu_read_lock();
	list_for_each_entry_rcu(chunk, &pool->chunks, next_chunk)
	avail += atomic_read(&chunk->avail);
	rcu_read_unlock();
	return avail;
	}
	EXPORT_SYMBOL_GPL(gen_pool_avail);

	/**
	* gen_pool_size - get size in bytes of memory managed by the pool
	* @pool: pool to get size
	*
	* Return size in bytes of memory managed by the pool.
	*/
	size_t gen_pool_size(struct gen_pool *pool)
	{
	struct gen_pool_chunk *chunk;
	size_t size = 0;

	rcu_read_lock();
	list_for_each_entry_rcu(chunk, &pool->chunks, next_chunk)
	size += chunk_size(chunk);
	rcu_read_unlock();
	return size;
	}
	EXPORT_SYMBOL_GPL(gen_pool_size);

	/**
	* gen_pool_set_algo - set the allocation algorithm
	* @pool: pool to change allocation algorithm
	* @algo: custom algorithm function
	* @data: additional data used by @algo
	*
	* Call @algo for each memory allocation in the pool.
	* If @algo is NULL use gen_pool_first_fit as default
	* memory allocation function.
	*/
	void gen_pool_set_algo(struct gen_pool pool, genpool_algo_t algo, void data)
	{
	rcu_read_lock();

	pool->algo = algo;
	if (!pool->algo)
	pool->algo = gen_pool_first_fit;

	pool->data = data;

	rcu_read_unlock();
	}
	EXPORT_SYMBOL(gen_pool_set_algo);

	/**
	* gen_pool_first_fit - find the first available region
	* of memory matching the size requirement (no alignment constraint)
	* @map: The address to base the search on
	* @size: The bitmap size in bits
	* @start: The bitnumber to start searching at
	* @nr: The number of zeroed bits we're looking for
	* @data: additional data - unused
	*/
	unsigned long gen_pool_first_fit(unsigned long *map, unsigned long size,
	unsigned long start, unsigned int nr, void *data)
	{
	return bitmap_find_next_zero_area(map, size, start, nr, 0);
	}
	EXPORT_SYMBOL(gen_pool_first_fit);

	/**
	* gen_pool_best_fit - find the best fitting region of memory
	* macthing the size requirement (no alignment constraint)
	* @map: The address to base the search on
	* @size: The bitmap size in bits
	* @start: The bitnumber to start searching at
	* @nr: The number of zeroed bits we're looking for
	* @data: additional data - unused
	*
	* Iterate over the bitmap to find the smallest free region
	* which we can allocate the memory.
	*/
	unsigned long gen_pool_best_fit(unsigned long *map, unsigned long size,
	unsigned long start, unsigned int nr, void *data)
	{
	unsigned long start_bit = size;
	unsigned long len = size + 1;
	unsigned long index;

	index = bitmap_find_next_zero_area(map, size, start, nr, 0);

	while (index < size) {
	int next_bit = find_next_bit(map, size, index + nr);
	if ((next_bit - index) < len) {
	len = next_bit - index;
	start_bit = index;
	if (len == nr)
	return start_bit;
	}
	index = bitmap_find_next_zero_area(map, size,
	next_bit + 1, nr, 0);
	}

	return start_bit;
	}
	EXPORT_SYMBOL(gen_pool_best_fit);

	static void devm_gen_pool_release(struct device dev, void res)
	{
	gen_pool_destroy((struct gen_pool *)res);
	}

	/**
	* devm_gen_pool_create - managed gen_pool_create
	* @dev: device that provides the gen_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. The pool will be
	* automatically destroyed by the device management code.
	*/
	struct gen_pool devm_gen_pool_create(struct device dev, int min_alloc_order,
	int nid)
	{
	struct gen_pool *ptr, pool;

	ptr = devres_alloc(devm_gen_pool_release, sizeof(*ptr), GFP_KERNEL);

	pool = gen_pool_create(min_alloc_order, nid);
	if (pool) {
	*ptr = pool;
	devres_add(dev, ptr);
	} else {
	devres_free(ptr);
	}

	return pool;
	}

	/**
	* dev_get_gen_pool - Obtain the gen_pool (if any) for a device
	* @dev: device to retrieve the gen_pool from
	* @name: Optional name for the gen_pool, usually NULL
	*
	* Returns the gen_pool for the device if one is present, or NULL.
	*/
	struct gen_pool dev_get_gen_pool(struct device dev)
	{
	struct gen_pool **p = devres_find(dev, devm_gen_pool_release, NULL,
	NULL);

	if (!p)
	return NULL;
	return *p;
	}
	EXPORT_SYMBOL_GPL(dev_get_gen_pool);

	#ifdef CONFIG_OF
	/**
	* of_get_named_gen_pool - find a pool by phandle property
	* @np: device node
	* @propname: property name containing phandle(s)
	* @index: index into the phandle array
	*
	* Returns the pool that contains the chunk starting at the physical
	* address of the device tree node pointed at by the phandle property,
	* or NULL if not found.
	*/
	struct gen_pool of_get_named_gen_pool(struct device_node np,
	const char *propname, int index)
	{
	struct platform_device *pdev;
	struct device_node *np_pool;

	np_pool = of_parse_phandle(np, propname, index);
	if (!np_pool)
	return NULL;
	pdev = of_find_device_by_node(np_pool);
	if (!pdev)
	return NULL;
	return dev_get_gen_pool(&pdev->dev);
	}
	EXPORT_SYMBOL_GPL(of_get_named_gen_pool);
	#endif /* CONFIG_OF */