1/* NOMMU mmap support for RomFS on MTD devices
2 *
3 * Copyright �� 2007 Red Hat, Inc. All Rights Reserved.
4 * Written by David Howells (dhowells@redhat.com)
5 *
6 * This program is free software; you can redistribute it and/or
7 * modify it under the terms of the GNU General Public License
8 * as published by the Free Software Foundation; either version
9 * 2 of the License, or (at your option) any later version.
10 */
11
12#include <linux/mm.h>
13#include <linux/mtd/super.h>
14#include "internal.h"
15
16/*
17 * try to determine where a shared mapping can be made
18 * - only supported for NOMMU at the moment (MMU can't doesn't copy private
19 *   mappings)
20 * - attempts to map through to the underlying MTD device
21 */
22static unsigned long romfs_get_unmapped_area(struct file *file,
23					     unsigned long addr,
24					     unsigned long len,
25					     unsigned long pgoff,
26					     unsigned long flags)
27{
28	struct inode *inode = file->f_mapping->host;
29	struct mtd_info *mtd = inode->i_sb->s_mtd;
30	unsigned long isize, offset;
31
32	if (!mtd)
33		goto cant_map_directly;
34
35	isize = i_size_read(inode);
36	offset = pgoff << PAGE_SHIFT;
37	if (offset > isize || len > isize || offset > isize - len)
38		return (unsigned long) -EINVAL;
39
40	/* we need to call down to the MTD layer to do the actual mapping */
41	if (mtd->get_unmapped_area) {
42		if (addr != 0)
43			return (unsigned long) -EINVAL;
44
45		if (len > mtd->size || pgoff >= (mtd->size >> PAGE_SHIFT))
46			return (unsigned long) -EINVAL;
47
48		offset += ROMFS_I(inode)->i_dataoffset;
49		if (offset > mtd->size - len)
50			return (unsigned long) -EINVAL;
51
52		return mtd->get_unmapped_area(mtd, len, offset, flags);
53	}
54
55cant_map_directly:
56	return (unsigned long) -ENOSYS;
57}
58
59/*
60 * permit a R/O mapping to be made directly through onto an MTD device if
61 * possible
62 */
63static int romfs_mmap(struct file *file, struct vm_area_struct *vma)
64{
65	return vma->vm_flags & (VM_SHARED | VM_MAYSHARE) ? 0 : -ENOSYS;
66}
67
68const struct file_operations romfs_ro_fops = {
69	.llseek			= generic_file_llseek,
70	.read			= do_sync_read,
71	.aio_read		= generic_file_aio_read,
72	.splice_read		= generic_file_splice_read,
73	.mmap			= romfs_mmap,
74	.get_unmapped_area	= romfs_get_unmapped_area,
75};
76