/* SPDX-License-Identifier: GPL-2.0 */
/*
 * ION Page Pool kernel interface header
 *
 * Copyright (C) 2011 Google, Inc.
 */

#ifndef _ION_PAGE_POOL_H
#define _ION_PAGE_POOL_H

#include <linux/mm_types.h>
#include <linux/mutex.h>
#include <linux/shrinker.h>
#include <linux/types.h>

/**
 * functions for creating and destroying a heap pool -- allows you
 * to keep a pool of pre allocated memory to use from your heap.  Keeping
 * a pool of memory that is ready for dma, ie any cached mapping have been
 * invalidated from the cache, provides a significant performance benefit on
 * many systems
 */

/**
 * struct ion_page_pool - pagepool struct
 * @high_count:		number of highmem items in the pool
 * @low_count:		number of lowmem items in the pool
 * @high_items:		list of highmem items
 * @low_items:		list of lowmem items
 * @mutex:		lock protecting this struct and especially the count
 *			item list
 * @gfp_mask:		gfp_mask to use from alloc
 * @order:		order of pages in the pool
 * @list:		plist node for list of pools
 *
 * Allows you to keep a pool of pre allocated pages to use from your heap.
 * Keeping a pool of pages that is ready for dma, ie any cached mapping have
 * been invalidated from the cache, provides a significant performance benefit
 * on many systems
 */
struct ion_page_pool {
	int high_count;
	int low_count;
	struct list_head high_items;
	struct list_head low_items;
	struct mutex mutex;
	gfp_t gfp_mask;
	unsigned int order;
	struct plist_node list;
};

struct ion_page_pool *ion_page_pool_create(gfp_t gfp_mask, unsigned int order);
void ion_page_pool_destroy(struct ion_page_pool *pool);
struct page *ion_page_pool_alloc(struct ion_page_pool *pool);
void ion_page_pool_free(struct ion_page_pool *pool, struct page *page);
int ion_page_pool_nr_pages(struct ion_page_pool *pool);

/** ion_page_pool_shrink - shrinks the size of the memory cached in the pool
 * @pool:		the pool
 * @gfp_mask:		the memory type to reclaim
 * @nr_to_scan:		number of items to shrink in pages
 *
 * returns the number of items freed in pages
 */
int ion_page_pool_shrink(struct ion_page_pool *pool, gfp_t gfp_mask,
			 int nr_to_scan);
#endif /* _ION_PAGE_POOL_H */