drivers/staging/android/ion/heaps/ion_system_contig_heap.c

// SPDX-License-Identifier: GPL-2.0
/*
 * ION Memory Allocator system contig heap exporter
 *
 * Copyright (C) 2019 Google, Inc.
 */

#include <asm/page.h>
#include <linux/dma-mapping.h>
#include <linux/err.h>
#include <linux/highmem.h>
#include <linux/ion.h>
#include <linux/mm.h>
#include <linux/module.h>
#include <linux/scatterlist.h>
#include <linux/slab.h>

static int ion_system_contig_heap_allocate(struct ion_heap *heap,
					   struct ion_buffer *buffer,
					   unsigned long len,
					   unsigned long flags)
{
	int order = get_order(len);
	struct page *page;
	struct sg_table *table;
	unsigned long i;
	int ret;

	page = alloc_pages(GFP_HIGHUSER | __GFP_ZERO | __GFP_NOWARN, order);
	if (!page)
		return -ENOMEM;

	split_page(page, order);

	len = PAGE_ALIGN(len);
	for (i = len >> PAGE_SHIFT; i < (1 << order); i++)
		__free_page(page + i);

	table = kmalloc(sizeof(*table), GFP_KERNEL);
	if (!table) {
		ret = -ENOMEM;
		goto free_pages;
	}

	ret = sg_alloc_table(table, 1, GFP_KERNEL);
	if (ret)
		goto free_table;

	sg_set_page(table->sgl, page, len, 0);

	buffer->sg_table = table;

	ion_buffer_prep_noncached(buffer);

	return 0;

free_table:
	kfree(table);
free_pages:
	for (i = 0; i < len >> PAGE_SHIFT; i++)
		__free_page(page + i);

	return ret;
}

static void ion_system_contig_heap_free(struct ion_buffer *buffer)
{
	struct sg_table *table = buffer->sg_table;
	struct page *page = sg_page(table->sgl);
	unsigned long pages = PAGE_ALIGN(buffer->size) >> PAGE_SHIFT;
	unsigned long i;

	for (i = 0; i < pages; i++)
		__free_page(page + i);
	sg_free_table(table);
	kfree(table);
}

static struct ion_heap_ops kmalloc_ops = {
	.allocate = ion_system_contig_heap_allocate,
	.free = ion_system_contig_heap_free,
};

static struct ion_heap contig_heap = {
	.ops = &kmalloc_ops,
	.type = ION_HEAP_TYPE_SYSTEM_CONTIG,
	.name = "ion_system_contig_heap",
};

static int __init ion_system_contig_heap_init(void)
{
	return ion_device_add_heap(&contig_heap);
}

static void __exit ion_system_contig_heap_exit(void)
{
	ion_device_remove_heap(&contig_heap);
}

module_init(ion_system_contig_heap_init);
module_exit(ion_system_contig_heap_exit);
MODULE_LICENSE("GPL v2");